2X or 1.4X converters on DSLRs, and the 'crop factor'

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

>Many people in the 35mm film arena suggest never using­ more than a
>1.4X converter because any imperfections in the lens (and th­e
converter)
>are magnified, along with losses in contrast, saturation, an­d so on.

Good advice for cheap lenses, but with high quality lenses and matched
t/c's you still get good results. We use a 2x with a 500 f/4 L IS
often and the image quality is very high, but the lens is very
expensive. With even a 100-400 L IS lens I'd expect poor results.

>If a DSLR already has a 'crop factor' of, say, 1.5 is the le­ns
already
>stressed to its maximum? Does the crop factor have the same ­effect on
lens
>quality as putting a converter on the lens for a 35mm film c­amera?

The 'crop factor' means you are using the sweet spot of the lens,
cropping off the edges where most problems show up, so it's the
opposite of what you say.

Bill

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

"Phil Stripling" <phil_stripling@cieux.zzn.com> wrote in message
news:3q3bwiae16.fsf@shell4.tdl.com...
> Another poster has asked about a 2X Quantaray converter on a zoom
> lens. Many people in the 35mm film arena suggest never using more than a
> 1.4X converter because any imperfections in the lens (and the converter)
> are magnified, along with losses in contrast, saturation, and so on.
>
> If a DSLR already has a 'crop factor' of, say, 1.5 is the lens already
> stressed to its maximum? Does the crop factor have the same effect on lens
> quality as putting a converter on the lens for a 35mm film camera?
> --
> Phil Stripling | email to the replyto address is presumed
> The Civilized Explorer | spam and read later. email from this URL
> http://www.cieux.com/ | http://www.civex.com/ is read daily.

Another reason to use a 1.4 rather than a 2x is that Canon's less than top
line cameras, film and digital, won't autofocus at a max aperture of less
than f5.6. A 2x on an f2.8 lens gets you that, a 1.4x on an f4 lens stays
within limits, but a 2x on an f5.6 lens may have problems. With a Canon
telelconverter, it won't AF, with an after market converter, you may have
metering problems, since those converters tell the camera that it's really
at f5.6, so you might end up underexposed by a stop or more. You can always
crank in some EC, of course.

--
Skip Middleton
http://www.shadowcatcherimagery.com

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

In article <3q3bwiae16.fsf@shell4.tdl.com>, Phil Stripling
<phil_stripling@cieux.zzn.com> wrote:

> Another poster has asked about a 2X Quantaray converter on a zoom
> lens. Many people in the 35mm film arena suggest never using more than a
> 1.4X converter because any imperfections in the lens (and the converter)
> are magnified, along with losses in contrast, saturation, and so on.
>
> If a DSLR already has a 'crop factor' of, say, 1.5 is the lens already
> stressed to its maximum? Does the crop factor have the same effect on lens
> quality as putting a converter on the lens for a 35mm film camera?

Well, using teleconverters is never going to improve the quality.

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

The amount of image degradation will be the same. You are simply using
less of the image circle, and if there is any change n effect al all it
would be that the digital is using less of the circle's edge which is never
as good as the center anyway.

--
http://www.chapelhillnoir.com
home of The Camera-ist's Manifesto
The Improved Links Pages are at
http://www.chapelhillnoir.com/links/mlinks00.html
A sample chapter from "Haight-Ashbury" is at
http://www.chapelhillnoir.com/writ/hait/hatitl.html

"Phil Stripling" <phil_stripling@cieux.zzn.com> wrote in message
news:3q3bwiae16.fsf@shell4.tdl.com...
> Another poster has asked about a 2X Quantaray converter on a zoom
> lens. Many people in the 35mm film arena suggest never using more than a
> 1.4X converter because any imperfections in the lens (and the converter)
> are magnified, along with losses in contrast, saturation, and so on.
>
> If a DSLR already has a 'crop factor' of, say, 1.5 is the lens already
> stressed to its maximum? Does the crop factor have the same effect on lens
> quality as putting a converter on the lens for a 35mm film camera?
> --
> Phil Stripling | email to the replyto address is presumed
> The Civilized Explorer | spam and read later. email from this URL
> http://www.cieux.com/ | http://www.civex.com/ is read daily.

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

In message <1107115324.125168.190570@f14g2000cwb.googlegroups.com>,
"Bill Hilton" <bhilton665@aol.com> wrote:

>>Many people in the 35mm film arena suggest never using?more than a
>>1.4X converter because any imperfections in the lens (and th?
>>converter)
>>are magnified, along with losses in contrast, saturation, an? so on.

>Good advice for cheap lenses, but with high quality lenses and matched
>t/c's you still get good results. We use a 2x with a 500 f/4 L IS
>often and the image quality is very high, but the lens is very
>expensive. With even a 100-400 L IS lens I'd expect poor results.

I've taken shots with my 100-400 and a Tamron 2x that were sharp enough,
though not spectacular. It usually involves stopping down, though.

With a D30 the 2x might do a lot better.

>>If a DSLR already has a 'crop factor' of, say, 1.5 is the le?s
>>already
>>stressed to its maximum? Does the crop factor have the same ?ffect on
>>lens
>>quality as putting a converter on the lens for a 35mm film c?mera?

>The 'crop factor' means you are using the sweet spot of the lens,
>cropping off the edges where most problems show up, so it's the
>opposite of what you say.

.... but you still are cutting the lens' resolution per frame height or
width by 33% with a 1.5x crop. The corners may be worse, full-frame, if
the quality dropoff at the corners is dramatic (more than 1.5x worse
than the corners of the crop). People seem to forget this fact in this
type of discussion.

--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><

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

In message <300120051416575885%rag@nospam.techline.com>,
Randall Ainsworth <rag@nospam.techline.com> wrote:

>In article <3q3bwiae16.fsf@shell4.tdl.com>, Phil Stripling
><phil_stripling@cieux.zzn.com> wrote:
>
>> Another poster has asked about a 2X Quantaray converter on a zoom
>> lens. Many people in the 35mm film arena suggest never using more than a
>> 1.4X converter because any imperfections in the lens (and the converter)
>> are magnified, along with losses in contrast, saturation, and so on.
>>
>> If a DSLR already has a 'crop factor' of, say, 1.5 is the lens already
>> stressed to its maximum? Does the crop factor have the same effect on lens
>> quality as putting a converter on the lens for a 35mm film camera?
>
>Well, using teleconverters is never going to improve the quality.

Yes they can, Archie. If you have a lens that is sharper than the
sensor (or film grain) can resolve, then a teleconverter will capture
more detail. I don't expect you to be able to comprehend this.
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><

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

Skip M wrote:
> Another reason to use a 1.4 rather than a 2x is that Canon's less
than top
> line cameras, film and digital, won't autofocus at a max aperture of
less
> than f5.6. A 2x on an f2.8 lens gets you that, a 1.4x on an f4 lens
stays
> within limits, but a 2x on an f5.6 lens may have problems. With a
Canon
> telelconverter, it won't AF, with an after market converter, you may
have
> metering problems, since those converters tell the camera that it's
really
> at f5.6, so you might end up underexposed by a stop or more.

No, it shouldn't. After the 2x, f/5.6 becomes effectively f/11. Even
though the converter doesn't tell the camera about this, and the camera
still assumes f/5.6, the light passes through f/11 effective. So the
meter sees less light. It does not need to know that it's because f/5.6
changed to f/11, but just concludes that the light gets dimmer and sets
the correct shutter speed and/or sensitivity.

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

<bj286@scn.org> wrote in message
news:1108848324.664673.167030@z14g2000cwz.googlegroups.com...
> Skip M wrote:
>> Another reason to use a 1.4 rather than a 2x is that Canon's less
> than top
>> line cameras, film and digital, won't autofocus at a max aperture of
> less
>> than f5.6. A 2x on an f2.8 lens gets you that, a 1.4x on an f4 lens
> stays
>> within limits, but a 2x on an f5.6 lens may have problems. With a
> Canon
>> telelconverter, it won't AF, with an after market converter, you may
> have
>> metering problems, since those converters tell the camera that it's
> really
>> at f5.6, so you might end up underexposed by a stop or more.
>
> No, it shouldn't. After the 2x, f/5.6 becomes effectively f/11. Even
> though the converter doesn't tell the camera about this, and the camera
> still assumes f/5.6, the light passes through f/11 effective. So the
> meter sees less light. It does not need to know that it's because f/5.6
> changed to f/11, but just concludes that the light gets dimmer and sets
> the correct shutter speed and/or sensitivity.
>
Really, I wouldn't have thunk it...

--
Skip Middleton
http://www.shadowcatcherimagery.com