Sign in with
Sign up | Sign in
Your question

Canon 5D and limited lens choices

Last response: in Digital Camera
Share
Anonymous
September 26, 2005 10:03:01 PM

Archived from groups: rec.photo.digital (More info?)

Canon "designed for digital" lenses which will cover a sensor the size
of a 35mm frame are pretty thin on the ground. This means early buyers
of 5D Canon DSLRs could experience "purple fringing" or Chromatic
Aberrations off the sensor's micro lenses far worse than 'crop factor'
camera users. Just using 'made for 35mm film' lenses will not overcome
the issue.

Of course all those Pro's using 1Ds Canon's and Kodak Pro DSLR cameras
already know about this effect and probably try to avoid situations
where this will occur. Pretty easy if you are a fashion photographer.

Action Photojournalists and sports photographers who often have no
choice in their subject location and buy a 5d thinking they'll get
better results will discover this problem real fast and go back to their
'crop factor' cameras.

Canon will point out (if you push them) the 5D is not a Professional
camera and they do market 2 different Pro camera so you have a choice of
which to use for what type of photography. Of course! It makes perfectly
good sense. The 1Ds for studio and controllable subjects and the 1D for
sports photographers... Now why didn't I think of that! The "s" on the
end of 1D is for "STUDIO".

The purple fringe problem occurs when adjacent photo detectors overload.
That is to say when the contrast range between the elements in a
photograph are outside that which the camera is capable of recording
detail in... Shooting a branch or building edge with bright sky will do
it as will shooting into the sun. Pretty much anything that will produce
CA in a lens, will add the sensor to the area of responsibility. CA from
the micro lenses is not yet fully understood (by me at any rate) but it
has been found to exist in laboratory tests.

Steve has some information most people should find easy to understand
(it's in picture form) about lens design to prevent or at least try to
prevent the problem ...which is currently being built into Olympus
digital lenses. http://www.steves-digicams.com/2004_reviews/e300_pg2.ht...

The Canon "S" series digital SLR lenses that are suitable for 300D, 350D
and 20D won't work on a 5D. I'd expect Sigma, Tokina and Tamron "made
for digital" lenses to pick up sales as people discover these are the
only currently offered digital lenses to fit a 5D.

--
Douglas...
Have gun will travel... Said his card.
I didn't care, I shot him anyway.
1/125th @ f5.6. R.I.P. Mamiya.
Anonymous
September 26, 2005 10:03:02 PM

Archived from groups: rec.photo.digital (More info?)

"Pix on Canvas" <canvaspix@yahoo.com.au> wrote in message
news:4337ab37$1@dnews.tpgi.com.au...
> Canon "designed for digital" lenses which will cover a sensor the size of
> a 35mm frame are pretty thin on the ground. This means early buyers of 5D
> Canon DSLRs could experience "purple fringing" or Chromatic Aberrations
> off the sensor's micro lenses far worse than 'crop factor' camera users.
> Just using 'made for 35mm film' lenses will not overcome the issue.
>

Any of Canon's standard EF lenses will work fine, of which they have quite a
large selection. What makes you say they won't?

Mark
Anonymous
September 26, 2005 10:03:02 PM

Archived from groups: rec.photo.digital (More info?)

In article <4337ab37$1@dnews.tpgi.com.au>,
Pix on Canvas <canvaspix@yahoo.com.au> wrote:
>Canon "designed for digital" lenses which will cover a sensor the size
>of a 35mm frame are pretty thin on the ground.

[snip scratched record]

Were your parents blown up by a cannon when you were young, leaving you with
lasting emotional damage, or something? I offer the following two tips which
may make you happier:

1) Don't buy one.

2) Get out more.
Related resources
Can't find your answer ? Ask !
Anonymous
September 26, 2005 10:03:02 PM

Archived from groups: rec.photo.digital (More info?)

Pix on Canvas wrote:
> Canon "designed for digital" lenses which will cover a sensor the size
> of a 35mm frame are pretty thin on the ground. This means early buyers
> of 5D Canon DSLRs could experience "purple fringing" or Chromatic
> Aberrations off the sensor's micro lenses far worse than 'crop factor'
> camera users. Just using 'made for 35mm film' lenses will not overcome
> the issue.

Perhaps you need to look at the thread titled:
Full-frame sensors can't do wide angle - NOT!

Check the link to the image below, a corner crop from a 12mm lens.
It proves chromatic aberration from the sensor's micro lenses
is not a factor.

In that thread David Littleboy said:
>>>Lenses designed specifically for digital sensors, direct the light at 90
>>>degrees to the sensor plane and avoid CA from the micro lenses on the
>>>sensor (or at least try to). Conventional film camera lenses direct
>>>light to the film at angles other than 90 degrees. This causes Chromatic
>>>Aberrations from the sensors themselves. Simple digital logic, Brian.
>>
>>Yeah, too bad angle of light incidence and chromatic aberration aren't
>>directly linked.
>>
>>Additionally, you fail to explain why angle of incidence would cause
>>color shift... because it doesn't.
>
>
> To say nothing of explaining how a high angle of incidence can even occur in
> a dSLR in which the rear element of the lens has to be far enough from the
> sensor to allow the mirror to swing, limiting the maximum angle of incidence
> to well within angles which microlenses have no problem handling. Oops.
>
> To reiterate, the high angle of incidence "problem" isn't a problem at, it's
> just is marketing FUD.
>
> If you don't believe that, crop out 2400 x 1980 pixels from the very upper
> right corner (the other corners are in shadow and too dark) of the following
> image, sharpen by 120%, r = 1.2, t = 0 (or whatever pleases), and print at
> 8x10. (This is an 8x10 crop from a 12x18 print.)
>
> http://dc.watch.impress.co.jp/cda/parts/image_for_link/...
>
> Of course, we'll hear a chorus of "it doesn't look all that great to me"
> from folks who bought into that fud, but anyone who's head isn't wedged up a
> warm dark place, and realizes that this is from a 12mm lens producing a full
> 12mm FOV, will have trouble getting their jaw off the floor.
>
> David J. Littleboy
> Tokyo, Japan
Anonymous
September 26, 2005 10:03:02 PM

Archived from groups: rec.photo.digital (More info?)

"Pix on Canvas" <canvaspix@yahoo.com.au> wrote in message
news:4337ab37$1@dnews.tpgi.com.au...
> snip

What makes you say this? This isn't not the first full frame DSLR produced
by Canon, it's their third. Have you seen this condition in the previous two
iterations? Have you tested any of their lenses with the 5D to determine if
any of what you say is true?

Sorry, I'm not buying any of this nonsense. If you can prove any of it,
please do so. Show me where a FF DSLR is more prone to fringing than a
sub-frame DSLR.
Anonymous
September 26, 2005 10:03:02 PM

Archived from groups: rec.photo.digital (More info?)

On 9/26/05 3:03 AM, in article 4337ab37$1@dnews.tpgi.com.au, "Pix on Canvas"
<canvaspix@yahoo.com.au> wrote:


>
> Of course all those Pro's using 1Ds Canon's and Kodak Pro DSLR cameras
> already know about this effect and probably try to avoid situations
> where this will occur. Pretty easy if you are a fashion photographer.
>

Most of your total BS snipped.
It's funny I use a Canon 1Ds and I don't "know" anything about this effect!
Others have already addressed the absurdity of your other claims so no need
to say anything further.
Do you even realize that you have turned into nothing more than a troll?
Anonymous
September 26, 2005 10:29:39 PM

Archived from groups: rec.photo.digital (More info?)

On Mon, 26 Sep 2005 13:59:10 +0000, C Wright wrote:

> On 9/26/05 3:03 AM, in article 4337ab37$1@dnews.tpgi.com.au, "Pix on Canvas"
> <canvaspix@yahoo.com.au> wrote:
>
>
>>
>> Of course all those Pro's using 1Ds Canon's and Kodak Pro DSLR cameras
>> already know about this effect and probably try to avoid situations
>> where this will occur. Pretty easy if you are a fashion photographer.
>>
>
> Most of your total BS snipped.
> It's funny I use a Canon 1Ds and I don't "know" anything about this effect!
> Others have already addressed the absurdity of your other claims so no need
> to say anything further.
> Do you even realize that you have turned into nothing more than a troll?
You got his point all wrong, it was his dress he was talking about.
--
Neil
Delete delete to reply by email
Anonymous
September 26, 2005 10:31:45 PM

Archived from groups: rec.photo.digital (More info?)

On Mon, 26 Sep 2005 10:29:37 +0000, Chris Brown wrote:

> In article <4337ab37$1@dnews.tpgi.com.au>,
> Pix on Canvas <canvaspix@yahoo.com.au> wrote:
>>Canon "designed for digital" lenses which will cover a sensor the size
>>of a 35mm frame are pretty thin on the ground.
>
> [snip scratched record]
>
> Were your parents blown up by a cannon when you were young, leaving you with
> lasting emotional damage, or something? I offer the following two tips which
> may make you happier:
>
> 1) Don't buy one.
>
> 2) Get out more.
Please don't inflict him on us - I would rather he stayed in more. The
smallest room comes to ming.

--
Neil
Delete delete to reply by email
September 26, 2005 11:18:26 PM

Archived from groups: rec.photo.digital (More info?)

On Mon, 26 Sep 2005 07:08:15 -0600, "Roger N. Clark (change username
to rnclark)" <username@qwest.net> wrote:

>Pix on Canvas wrote:
>> Canon "designed for digital" lenses which will cover a sensor the size
>> of a 35mm frame are pretty thin on the ground. This means early buyers
>> of 5D Canon DSLRs could experience "purple fringing" or Chromatic
>> Aberrations off the sensor's micro lenses far worse than 'crop factor'
>> camera users. Just using 'made for 35mm film' lenses will not overcome
>> the issue.
>
>Perhaps you need to look at the thread titled:
> Full-frame sensors can't do wide angle - NOT!
>
>Check the link to the image below, a corner crop from a 12mm lens.
>It proves chromatic aberration from the sensor's micro lenses
>is not a factor.
>
>In that thread David Littleboy said:
> >>>Lenses designed specifically for digital sensors, direct the light at 90
> >>>degrees to the sensor plane and avoid CA from the micro lenses on the
> >>>sensor (or at least try to). Conventional film camera lenses direct
> >>>light to the film at angles other than 90 degrees. This causes Chromatic
> >>>Aberrations from the sensors themselves. Simple digital logic, Brian.
> >>
> >>Yeah, too bad angle of light incidence and chromatic aberration aren't
> >>directly linked.
> >>
> >>Additionally, you fail to explain why angle of incidence would cause
> >>color shift... because it doesn't.
> >
> >
> > To say nothing of explaining how a high angle of incidence can even occur in
> > a dSLR in which the rear element of the lens has to be far enough from the
> > sensor to allow the mirror to swing, limiting the maximum angle of incidence
> > to well within angles which microlenses have no problem handling. Oops.
> >
> > To reiterate, the high angle of incidence "problem" isn't a problem at, it's
> > just is marketing FUD.
> >
> > If you don't believe that, crop out 2400 x 1980 pixels from the very upper
> > right corner (the other corners are in shadow and too dark) of the following
> > image, sharpen by 120%, r = 1.2, t = 0 (or whatever pleases), and print at
> > 8x10. (This is an 8x10 crop from a 12x18 print.)
> >
> > http://dc.watch.impress.co.jp/cda/parts/image_for_link/...

Kind of clear that there is CA going on in this image. Check the
> >
> > Of course, we'll hear a chorus of "it doesn't look all that great to me"
> > from folks who bought into that fud, but anyone who's head isn't wedged up a
> > warm dark place, and realizes that this is from a 12mm lens producing a full
> > 12mm FOV, will have trouble getting their jaw off the floor.
> >
> > David J. Littleboy
> > Tokyo, Japan
Anonymous
September 27, 2005 12:16:57 AM

Archived from groups: rec.photo.digital (More info?)

"Pix on Canvas" <canvaspix@yahoo.com.au> wrote in message
news:4337ab37$1@dnews.tpgi.com.au...
> Canon "designed for digital" lenses which will cover a sensor the size
> of a 35mm frame are pretty thin on the ground. This means early buyers

Of course they're thin on the ground you tit.
'Designed for digital' lenses are designed for less than full frame sensors,
not a full frame sensor, such as in the 5D.

And the rest of your ramblings: utter deluded ramblings.

Go away.
Anonymous
September 27, 2005 12:44:02 AM

Archived from groups: rec.photo.digital (More info?)

Mark B. wrote:
> "Pix on Canvas" <canvaspix@yahoo.com.au> wrote in message
> news:4337ab37$1@dnews.tpgi.com.au...
>
>>Canon "designed for digital" lenses which will cover a sensor the size of
>>a 35mm frame are pretty thin on the ground. This means early buyers of 5D
>>Canon DSLRs could experience "purple fringing" or Chromatic Aberrations
>>off the sensor's micro lenses far worse than 'crop factor' camera users.
>>Just using 'made for 35mm film' lenses will not overcome the issue.
>>
>
>
> Any of Canon's standard EF lenses will work fine, of which they have quite a
> large selection. What makes you say they won't?
>
> Mark
>
>
Didn't say the existing lenses "won't" work. I said because of their
design they will probably produce more purple fringing than the smaller
sensors. No doubt Canon will address this issue when there is a
groundswell of complaints and not before.

--
Douglas...
Have gun will travel... Said his card.
I didn't care, I shot him anyway.
1/125th @ f5.6. R.I.P. Mamiya.
Anonymous
September 27, 2005 8:09:07 AM

Archived from groups: rec.photo.digital (More info?)

In article <4337ab37$1@dnews.tpgi.com.au>, canvaspix@yahoo.com.au
says...
> The purple fringe problem occurs when adjacent photo detectors overload.
> That is to say when the contrast range between the elements in a
> photograph are outside that which the camera is capable of recording
> detail in... Shooting a branch or building edge with bright sky will do
> it as will shooting into the sun. Pretty much anything that will produce
> CA in a lens, will add the sensor to the area of responsibility. CA from
> the micro lenses is not yet fully understood (by me at any rate) but it
> has been found to exist in laboratory tests.

Yeah... no. "Blooming" doesn't occur with modern CCD or CMOS sensors...
so, no... you lose, sorry.
--
http://www.pbase.com/bcbaird
Anonymous
September 27, 2005 9:43:11 AM

Archived from groups: rec.photo.digital (More info?)

Gormless wrote:
> "Pix on Canvas" <canvaspix@yahoo.com.au> wrote in message
> news:4337ab37$1@dnews.tpgi.com.au...
>
>>Canon "designed for digital" lenses which will cover a sensor the size
>>of a 35mm frame are pretty thin on the ground. This means early buyers
>
>
> Of course they're thin on the ground you tit.
> 'Designed for digital' lenses are designed for less than full frame sensors,
> not a full frame sensor, such as in the 5D.
>
> And the rest of your ramblings: utter deluded ramblings.
>
> Go away.
>
>
>
It's very curious that all the replies here are personal attacks. Could
it be that the EOS devotees are so (un)knowledgeable about their
interest that they have no understanding of the issue? Quite likely.

At least half of the images offered as examples of how good the camera
is, have substantial flaws yet a lot of 'gatta-haves are about to sell
the family jewels to buy one. The rest of you probably deserve Canon
products.

--
Douglas...
Anonymous
September 27, 2005 9:43:12 AM

Archived from groups: rec.photo.digital (More info?)

"Pix on Canvas" <canvaspix@yahoo.com.au> wrote in message
news:43384f52$1@dnews.tpgi.com.au...
> It's very curious that all the replies here are personal attacks. Could it
> be that the EOS devotees are so (un)knowledgeable about their interest
> that they have no understanding of the issue? Quite likely.
>
> At least half of the images offered as examples of how good the camera is,
> have substantial flaws yet a lot of 'gatta-haves are about to sell the
> family jewels to buy one. The rest of you probably deserve Canon products.
>

You've offered no proof of what you are claiming, other than some sweeping
statements:

> Of course all those Pro's using 1Ds Canon's and Kodak Pro DSLR cameras
> already know about this effect and probably try to avoid situations where
> this will occur. Pretty easy if you are a fashion photographer.

Can you offer any examples?

You also state the obvious:

> The Canon "S" series digital SLR lenses that are suitable for 300D, 350D
> and 20D won't work on a 5D

Not only are they unsuitable, they have an entirely different mount and
physically will not work.

But this statement has me puzzled:

>I'd expect Sigma, Tokina and Tamron "made for digital" lenses to pick up
>sales as people discover these are the only currently offered digital
>lenses to fit a 5D.

The 'designed for digital' lenses by 3rd party lens makers are specifically
meant for <full frame sensors, and it's generally listed in their specs. I
would expect anyone spending more than $3k on a body would know that. So
I'm curious how you arrive at the conclusion they are the only lenses to fit
the 5D.

Mark
Anonymous
September 27, 2005 9:43:12 AM

Archived from groups: rec.photo.digital (More info?)

In article <43384f52$1@dnews.tpgi.com.au>,
Pix on Canvas <canvaspix@yahoo.com.au> wrote:
>
>At least half of the images offered as examples of how good the camera
>is, have substantial flaws yet a lot of 'gatta-haves are about to sell
>the family jewels to buy one. The rest of you probably deserve Canon
>products.

OK, how about you leave us soon-to-be 5D owners to our soon-to-be miserable
contemplation on having wasted so much money on an obvious lemon? You've
warned us all about this critical flaw, and we don't seem to be listening to
your cautionary tales about how this non-lens-related, lens-related effect
is going to ruin all our photos. We're obviously beyond help. You can go now
if you like...
Anonymous
September 27, 2005 5:02:00 PM

Archived from groups: rec.photo.digital (More info?)

>Action Photojournalists and sports photographers who often have no
>choice in their subject location and buy a 5d thinking they'll get
>better results will discover this problem real fast and go back to their
>'crop factor' cameras.

How many sports shooters will be buying the 5D for better results?
ZERO.
Duh!

Perhaps you meant "slower results?"
The rest of your trollish post is equally nonsensical.
Anonymous
September 27, 2005 11:01:52 PM

Archived from groups: rec.photo.digital (More info?)

"Pix on Canvas" <canvaspix@yahoo.com.au> wrote in message
news:43384f52$1@dnews.tpgi.com.au...
> >
> It's very curious that all the replies here are personal attacks. Could

And rightly so - you don't know what you're talking about so we have to
attack you personally. Simple.
Anonymous
September 27, 2005 11:11:13 PM

Archived from groups: rec.photo.digital (More info?)

"Pix on Canvas" <canvaspix@yahoo.com.au> wrote in message
news:4337ab37$1@dnews.tpgi.com.au...
> Canon "designed for digital" lenses which will cover a sensor the size of
> a 35mm frame are pretty thin on the ground. This means early buyers of 5D
> Canon DSLRs could experience "purple fringing" or Chromatic Aberrations
> off the sensor's micro lenses far worse than 'crop factor' camera users.
> Just using 'made for 35mm film' lenses will not overcome the issue.
>
> Of course all those Pro's using 1Ds Canon's and Kodak Pro DSLR cameras
> already know about this effect and probably try to avoid situations where
> this will occur. Pretty easy if you are a fashion photographer.
>
> Action Photojournalists and sports photographers who often have no choice
> in their subject location and buy a 5d thinking they'll get better results
> will discover this problem real fast and go back to their 'crop factor'
> cameras.
>
> Canon will point out (if you push them) the 5D is not a Professional
> camera and they do market 2 different Pro camera so you have a choice of
> which to use for what type of photography. Of course! It makes perfectly
> good sense. The 1Ds for studio and controllable subjects and the 1D for
> sports photographers... Now why didn't I think of that! The "s" on the end
> of 1D is for "STUDIO".
>
> The purple fringe problem occurs when adjacent photo detectors overload.
> That is to say when the contrast range between the elements in a
> photograph are outside that which the camera is capable of recording
> detail in... Shooting a branch or building edge with bright sky will do it
> as will shooting into the sun. Pretty much anything that will produce CA
> in a lens, will add the sensor to the area of responsibility. CA from the
> micro lenses is not yet fully understood (by me at any rate) but it has
> been found to exist in laboratory tests.
>
> Steve has some information most people should find easy to understand
> (it's in picture form) about lens design to prevent or at least try to
> prevent the problem ...which is currently being built into Olympus digital
> lenses. http://www.steves-digicams.com/2004_reviews/e300_pg2.ht...
>
> The Canon "S" series digital SLR lenses that are suitable for 300D, 350D
> and 20D won't work on a 5D. I'd expect Sigma, Tokina and Tamron "made for
> digital" lenses to pick up sales as people discover these are the only
> currently offered digital lenses to fit a 5D.
>

I have only heard of the EF 14mm showing much of a problem, even then it
might just be lens CA. Most people using the 1Ds do not have problems,
unless you are paranoid enough to think they are concealing it.

Telecentric lens designs would help but I don't think are the limiting
factor yet.
September 28, 2005 4:56:50 AM

Archived from groups: rec.photo.digital (More info?)

Pix on Canvas wrote:


> It's very curious that all the replies here are personal attacks.

You didn't post "Canon is the only camera people should buy" so of course
you get personally insulted. You expected something else?

--

Stacey
Anonymous
September 28, 2005 6:07:28 PM

Archived from groups: rec.photo.digital (More info?)

Kennedy,

A purely educational question. You talk about 'telecentric' lens
designs.
I had never heard of this and looked it up on the web. From what
I could understand, a telecentric lens maps objects of the same
dimension
to the same size on the film plane regardless of object distance from
lens (i.e.
no 'perspective distortion'). Is that what you are referring to or
something different?

Kennedy McEwen wrote:
> In article <341_e.10010$w74.7940@trndny05>, SamSez
> <samtheman@verizon.net> writes
> >
> >So then why do Sigma, Tamron, Nikon, and yes, [lower your head respectfully],
> >even Canon, all use the phrase 'Optimized for digital SLR*' for SOME, but not
> >all of their products???
>
> Because most of the lenses bearing this tag are designed for a smaller
> field coverage, eg. all of Canon's EF-S range, and therefore do not need
> the overhead in glass, mount and movement that is requird to cover the
> full field. Sure, some of them are allegedly closer to telecentric
> design, but then most wide angle lenses for SLRs have to be closer to
> telecentric than those for P&S cameras simply to provide enough room for
> the mirror to flip out of the light path when the exposure is made. All
> such inverse telephoto (where the distance from the optical centre to
> the focal plane is longer than the focal length) designs are partially
> telecentric - it is a consequence of the geometry. For focal lengths
> greater than the mirror height, the non-telecentricity is negligible in
> term of the ray-bundle offset between the filter and the silicon, which
> gives rise to the CA you are sputtering about. In short, the problem is
> negligible in an SLR design in any case, although it may well be a
> problem with P&S cameras, particularly small pixel devices.
> --
> Kennedy
> Yes, Socrates himself is particularly missed;
> A lovely little thinker, but a bugger when he's pissed.
> Python Philosophers (replace 'nospam' with 'kennedym' when replying)
Anonymous
September 28, 2005 10:48:09 PM

Archived from groups: rec.photo.digital (More info?)

In article <341_e.10010$w74.7940@trndny05>, SamSez
<samtheman@verizon.net> writes
>
>So then why do Sigma, Tamron, Nikon, and yes, [lower your head respectfully],
>even Canon, all use the phrase 'Optimized for digital SLR*' for SOME, but not
>all of their products???

Because most of the lenses bearing this tag are designed for a smaller
field coverage, eg. all of Canon's EF-S range, and therefore do not need
the overhead in glass, mount and movement that is requird to cover the
full field. Sure, some of them are allegedly closer to telecentric
design, but then most wide angle lenses for SLRs have to be closer to
telecentric than those for P&S cameras simply to provide enough room for
the mirror to flip out of the light path when the exposure is made. All
such inverse telephoto (where the distance from the optical centre to
the focal plane is longer than the focal length) designs are partially
telecentric - it is a consequence of the geometry. For focal lengths
greater than the mirror height, the non-telecentricity is negligible in
term of the ray-bundle offset between the filter and the silicon, which
gives rise to the CA you are sputtering about. In short, the problem is
negligible in an SLR design in any case, although it may well be a
problem with P&S cameras, particularly small pixel devices.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)
Anonymous
September 28, 2005 11:28:00 PM

Archived from groups: rec.photo.digital (More info?)

Kennedy,

Thanks for the explanation. The only thing that still puzzles me is
this:
If a lens is fully telecentric, wouldn't that mean that a one foot
ruler
that was let's say 2 feet from the lens and a one foot ruler that was
4 feet from the lens would produced the same size image on the film
plane
(assuming they are within the depth of field)?
Wouldn't that lead to strange looking images? Or is it that when you
refer
to 'partially telecentric' you are saying that we are somewhere in
between
where perspective is maintained but the variation in angle of the
principle rays to the film plane is minimized?

Thanks again


Kennedy McEwen wrote:
> In article <1127941648.059540.293340@f14g2000cwb.googlegroups.com>,
> "winhag@yahoo.com" <winhag@yahoo.com> writes
> >Kennedy,
> >
> >A purely educational question. You talk about 'telecentric' lens
> >designs.
> >I had never heard of this and looked it up on the web. From what
> >I could understand, a telecentric lens maps objects of the same
> >dimension
> >to the same size on the film plane regardless of object distance from
> >lens (i.e.
> >no 'perspective distortion'). Is that what you are referring to or
> >something different?
> >
> Yes.
>
> If you draw out a simple lens then all of the principle rays (the
> principle ray is the central ray in the bundle) to every point between
> the object and its image on the focal plane passes through the centre of
> the lens. This means that there is only one point in the image where
> the principle ray is perpendicular to the focal plane - the centre of
> the focal plane. At every other point on the focal plane, the principle
> ray diverges from the centre. The easiest way to visualise this is just
> to draw a lens with an object and its image on a sheet of paper and then
> draw in the principle rays from the object to the image, making sure
> that they all pass through the centre of the lens. Now, if the angle of
> incidence at the focal plane is not 90deg, there is a chance that some
> of the light passing through the filter will actually land on an
> adjacent pixel rather than the pixel some small distance under the
> filter, and this causes colour distortions because the camera expects
> all of the light falling on certain pixels to have been filtered to the
> appropriate colour. Obviously the greater the angle from perpendicular
> of the principle ray, and the lower the f/# (ie. the wider the cone
> formed by the bundle of incident rays around the principle one), then
> the more light that can 'leak' into adjacent pixels this way.#
>
> With a telecentric lens, all of the principle rays reaching the focal
> plane are perpendicular to it and, since the same f/# must be produced
> across the focal plane, this means that each point of the image does not
> use all of the available lens aperture - so the rear lens elements are
> physically larger than would be required normally. Of course, that
> means that all of the rays incident at the corner of the focal plane are
> coming from the periphery of the lens, making it more difficult to
> control all aberations, not just chromatic. So telecentric lenses tend
> to have a poorer performance than conventional designs - or they are
> much more expensive for the same performance. The main reason for
> producing such a lens in pre-digital days was, as you have found in your
> net search, to ensure that images did not change size when the system
> was focus was moved. This would be important in instruments measuring
> dimensions directly from the image. However, since telecentricity means
> that the principle ray to every point in the image is perpendicular to
> the focal plane, there is an argument that it is ideal in digital
> sensors to ensure that the amount of leakage from one filter to adjacent
> pixels is fixed - although it does still change with f/# of course.
>
> In most cases though the CA from non-telecentric lenses argument is
> overhyped and you just need to examine the pixel dimensions to see how
> spurious it is. Based on the minimum back working distance to clear the
> mirror, which is proportional to the sensor size, the angle of incidence
> in the corner of the field for the principle ray from this worst case
> situation is almost the same in both formats - leaving only the pixel
> dimension as being the critical parameter. Smaller format sensors
> usually have smaller pixels and they consequently suffer more from this
> problem than larger sensors - completely contrary to the hype.
>
> However, putting this all into perspective, the semi-angle of the light
> cone itself with a fast optic is about the same angle as the worst case
> off-perpendiularity of the non-telecentric lens. So even a perfect
> "designed for digital" fully telecentric lens will produce the same
> colour distortion across the entire field as the worst case simple lens
> will produce at the corner. Added to which, that worst case only occurs
> at one particular focal length - shorter focal length lenses than this
> are partially telecentric because of their inverse telephoto design
> keeping the principle ray closer to perpendicular even in the corner of
> the frame, whilst longer focal length lenses produce principle rays
> closer to perpendicular in any case.
>
> In short, the entire CA argument (and this is one of the cornerstones of
> the entire 4/3 strategy!) is based on nothing more than hype. 4/3 and
> APS formats are there because they are cheaper to make, not because they
> or their optics are intrinsically superior.
>
> If there is CA in the image then it is almost entirely coming from the
> lens, just in the same way as it did on good old analogue colour film
> where, incidentally, the distance between the layers of emulsion isn't
> too different from the distance between the filter and silicon in a CCD
> or CMOS sensor.
>
> Yes, this issue will eventually become a problem, when pixel sizes get
> down to 3um or less on these larger focal planes, but obviously the
> smaller 4/3 and APS cameras will need to be there a long time before
> full frame cameras do, just on the pixel count wars alone. And to make
> it worse, these small size pixels will be restricted to faster minimum
> apertures (as they currently are in P&S cameras) to take full advantage
> of the pixel count in terms of real resolution, making the CA problem
> even more significant - telecentric lenses or not.
> --
> Kennedy
> Yes, Socrates himself is particularly missed;
> A lovely little thinker, but a bugger when he's pissed.
> Python Philosophers (replace 'nospam' with 'kennedym' when replying)
Anonymous
September 29, 2005 4:18:28 AM

Archived from groups: rec.photo.digital (More info?)

In article <1127941648.059540.293340@f14g2000cwb.googlegroups.com>,
"winhag@yahoo.com" <winhag@yahoo.com> writes
>Kennedy,
>
>A purely educational question. You talk about 'telecentric' lens
>designs.
>I had never heard of this and looked it up on the web. From what
>I could understand, a telecentric lens maps objects of the same
>dimension
>to the same size on the film plane regardless of object distance from
>lens (i.e.
>no 'perspective distortion'). Is that what you are referring to or
>something different?
>
Yes.

If you draw out a simple lens then all of the principle rays (the
principle ray is the central ray in the bundle) to every point between
the object and its image on the focal plane passes through the centre of
the lens. This means that there is only one point in the image where
the principle ray is perpendicular to the focal plane - the centre of
the focal plane. At every other point on the focal plane, the principle
ray diverges from the centre. The easiest way to visualise this is just
to draw a lens with an object and its image on a sheet of paper and then
draw in the principle rays from the object to the image, making sure
that they all pass through the centre of the lens. Now, if the angle of
incidence at the focal plane is not 90deg, there is a chance that some
of the light passing through the filter will actually land on an
adjacent pixel rather than the pixel some small distance under the
filter, and this causes colour distortions because the camera expects
all of the light falling on certain pixels to have been filtered to the
appropriate colour. Obviously the greater the angle from perpendicular
of the principle ray, and the lower the f/# (ie. the wider the cone
formed by the bundle of incident rays around the principle one), then
the more light that can 'leak' into adjacent pixels this way.#

With a telecentric lens, all of the principle rays reaching the focal
plane are perpendicular to it and, since the same f/# must be produced
across the focal plane, this means that each point of the image does not
use all of the available lens aperture - so the rear lens elements are
physically larger than would be required normally. Of course, that
means that all of the rays incident at the corner of the focal plane are
coming from the periphery of the lens, making it more difficult to
control all aberations, not just chromatic. So telecentric lenses tend
to have a poorer performance than conventional designs - or they are
much more expensive for the same performance. The main reason for
producing such a lens in pre-digital days was, as you have found in your
net search, to ensure that images did not change size when the system
was focus was moved. This would be important in instruments measuring
dimensions directly from the image. However, since telecentricity means
that the principle ray to every point in the image is perpendicular to
the focal plane, there is an argument that it is ideal in digital
sensors to ensure that the amount of leakage from one filter to adjacent
pixels is fixed - although it does still change with f/# of course.

In most cases though the CA from non-telecentric lenses argument is
overhyped and you just need to examine the pixel dimensions to see how
spurious it is. Based on the minimum back working distance to clear the
mirror, which is proportional to the sensor size, the angle of incidence
in the corner of the field for the principle ray from this worst case
situation is almost the same in both formats - leaving only the pixel
dimension as being the critical parameter. Smaller format sensors
usually have smaller pixels and they consequently suffer more from this
problem than larger sensors - completely contrary to the hype.

However, putting this all into perspective, the semi-angle of the light
cone itself with a fast optic is about the same angle as the worst case
off-perpendiularity of the non-telecentric lens. So even a perfect
"designed for digital" fully telecentric lens will produce the same
colour distortion across the entire field as the worst case simple lens
will produce at the corner. Added to which, that worst case only occurs
at one particular focal length - shorter focal length lenses than this
are partially telecentric because of their inverse telephoto design
keeping the principle ray closer to perpendicular even in the corner of
the frame, whilst longer focal length lenses produce principle rays
closer to perpendicular in any case.

In short, the entire CA argument (and this is one of the cornerstones of
the entire 4/3 strategy!) is based on nothing more than hype. 4/3 and
APS formats are there because they are cheaper to make, not because they
or their optics are intrinsically superior.

If there is CA in the image then it is almost entirely coming from the
lens, just in the same way as it did on good old analogue colour film
where, incidentally, the distance between the layers of emulsion isn't
too different from the distance between the filter and silicon in a CCD
or CMOS sensor.

Yes, this issue will eventually become a problem, when pixel sizes get
down to 3um or less on these larger focal planes, but obviously the
smaller 4/3 and APS cameras will need to be there a long time before
full frame cameras do, just on the pixel count wars alone. And to make
it worse, these small size pixels will be restricted to faster minimum
apertures (as they currently are in P&S cameras) to take full advantage
of the pixel count in terms of real resolution, making the CA problem
even more significant - telecentric lenses or not.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)
Anonymous
September 29, 2005 7:17:06 PM

Archived from groups: rec.photo.digital (More info?)

Kennedy,

Again thanks. I think I understand it now. I believe my confusion
was created by other sites which talked about lenses that were
telecentric in both the object and image plane. Your explanation
coupled with the explanation here:
http://www.edmundoptics.com/techsupport/DisplayArticle....

helped clear it up. It sounds like you're talking about lenses which
are telecentric on the image side only.
Thanks again for taking the time!


Kennedy McEwen wrote:
> In article <1127960880.935146.226250@g43g2000cwa.googlegroups.com>,
> "winhag@yahoo.com" <winhag@yahoo.com> writes
> >Kennedy,
> >
> >Thanks for the explanation. The only thing that still puzzles me is
> >this:
> >If a lens is fully telecentric, wouldn't that mean that a one foot
> >ruler
> >that was let's say 2 feet from the lens and a one foot ruler that was
> >4 feet from the lens would produced the same size image on the film
> >plane
> >(assuming they are within the depth of field)?
> >Wouldn't that lead to strange looking images?
>
> Not really. Perspective is still present, but the lens is just designed
> so that the principle ray is perpendicular to the focal plane, so that
> as focus moves from one plane to another, the images that are out of
> focus don't change size when they become sharp.
>
> One way to think about this, although not particularly accurate, is that
> the telecentric lens is just a conventional lens with an additional
> group at the back which bends all of the ray bundles back towards the
> optic axis by an amount proportional to their distance from the axis.
> The inaccuracy lies in the fact that the additional group obviously has
> some optical power, since all it would be is a spherical surface element
> itself, so that has to be compensated in the main image forming part of
> the lens, but that is unnecessary to explain the basic principle. The
> ray bundles still all come to a focus at the focal plane, but they are
> all symmetrical around the perpendicular to the plane. So the image
> just looks like a normal image, with correct perspective, but things
> don't change size as they pass through focus.
>
> You have probably seen the non-telecentric effect in the past without
> thinking it was odd. Take a wide angle lens (where the effect is most
> significant) and view a wall through the finder, noting where the edges
> of the frame are on the wall. Now adjust the focus from infinity to the
> closest range. With a non-telecentric lens, the edge of the frame will
> move in relative to the wall as the lens is focussed closer. This is
> because the principle rays at the edge of the frame are not
> perpendicular to the focal plane, so when the lens moves further from
> the focal plane to focus closer the rays that previously reached the
> edge now fall outside of the image frame. A telecentric lens would not
> do this - as you focus from infinity down to the closest range the edges
> of the frame would not change position. Everything still goes in and
> out of focus and has the same perspective, but their size does not
> change as the focus changes.
> --
> Kennedy
> Yes, Socrates himself is particularly missed;
> A lovely little thinker, but a bugger when he's pissed.
> Python Philosophers (replace 'nospam' with 'kennedym' when replying)
Anonymous
September 29, 2005 8:41:29 PM

Archived from groups: rec.photo.digital (More info?)

In article <1127960880.935146.226250@g43g2000cwa.googlegroups.com>,
"winhag@yahoo.com" <winhag@yahoo.com> writes
>Kennedy,
>
>Thanks for the explanation. The only thing that still puzzles me is
>this:
>If a lens is fully telecentric, wouldn't that mean that a one foot
>ruler
>that was let's say 2 feet from the lens and a one foot ruler that was
>4 feet from the lens would produced the same size image on the film
>plane
>(assuming they are within the depth of field)?
>Wouldn't that lead to strange looking images?

Not really. Perspective is still present, but the lens is just designed
so that the principle ray is perpendicular to the focal plane, so that
as focus moves from one plane to another, the images that are out of
focus don't change size when they become sharp.

One way to think about this, although not particularly accurate, is that
the telecentric lens is just a conventional lens with an additional
group at the back which bends all of the ray bundles back towards the
optic axis by an amount proportional to their distance from the axis.
The inaccuracy lies in the fact that the additional group obviously has
some optical power, since all it would be is a spherical surface element
itself, so that has to be compensated in the main image forming part of
the lens, but that is unnecessary to explain the basic principle. The
ray bundles still all come to a focus at the focal plane, but they are
all symmetrical around the perpendicular to the plane. So the image
just looks like a normal image, with correct perspective, but things
don't change size as they pass through focus.

You have probably seen the non-telecentric effect in the past without
thinking it was odd. Take a wide angle lens (where the effect is most
significant) and view a wall through the finder, noting where the edges
of the frame are on the wall. Now adjust the focus from infinity to the
closest range. With a non-telecentric lens, the edge of the frame will
move in relative to the wall as the lens is focussed closer. This is
because the principle rays at the edge of the frame are not
perpendicular to the focal plane, so when the lens moves further from
the focal plane to focus closer the rays that previously reached the
edge now fall outside of the image frame. A telecentric lens would not
do this - as you focus from infinity down to the closest range the edges
of the frame would not change position. Everything still goes in and
out of focus and has the same perspective, but their size does not
change as the focus changes.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)
Anonymous
September 30, 2005 12:17:07 AM

Archived from groups: rec.photo.digital (More info?)

Brian Baird <no@no.thank.u> wrote:
> In article <4337ab37$1@dnews.tpgi.com.au>, canvaspix@yahoo.com.au
> says...
>> The purple fringe problem occurs when adjacent photo detectors overload.
>> That is to say when the contrast range between the elements in a
>> photograph are outside that which the camera is capable of recording
>> detail in... Shooting a branch or building edge with bright sky will do
>> it as will shooting into the sun. Pretty much anything that will produce
>> CA in a lens, will add the sensor to the area of responsibility. CA from
>> the micro lenses is not yet fully understood (by me at any rate) but it
>> has been found to exist in laboratory tests.
>
> Yeah... no. "Blooming" doesn't occur with modern CCD or CMOS sensors...
> so, no... you lose, sorry.

Er, do you have something to support that? Granted, it generally
isn't much of an issue with a decent lens, but I've had signs of
blooming on my 20D even with the 85mm f/1.8, which is about as good a
lens and as modern a CMOS as you can get.

The primary culprit is usually small leaves against bright sky, and
under magnification blooming is visible all the way around the leaf,
showing that it isn't just CA.

Perhaps you meant to say that modern microlenses don't contribute
anything significant to the problem? That I find quite plausible.

--
Zed Pobre <zed@resonant.org> a.k.a. Zed Pobre <zed@debian.org>
PGP key and fingerprint available on finger; encrypted mail welcomed.
!