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Analog Lens F stop low light for digital

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Anonymous
April 19, 2005 4:31:31 PM

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

If you put a 400mm analog lens on a digital SLR camera, you will have
around a 600mm lens.

Our 400mm lens is F 4.5-.6.7 which is pretty low light.

Could anyone comment on just how restricted the lens would be shooting
at 600mm.

Using the 400mm on our analog Canon in Africa, has been working pretty
well. The results have been ok for our armature photography skills and
taste. .

But, I was wondering that with the 1.5x conversion and the low F stops,
shooting with 400m converted to 600m would make shooting with this lens
hard to do, like very obviously too low a light conditions at sunset or
early sunrise.

Daytime should be ok?

Thanks, Jon
April 19, 2005 4:56:31 PM

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

It has no impact. It's just like shooting film & cropping the edges off
then printing larger. That's the only difference. In fact for a 6MP
camera, you probably could get the same print with a cropped 35mm film
print.

scubatv wrote:

> If you put a 400mm analog lens on a digital SLR camera, you will have
> around a 600mm lens.
>
> Our 400mm lens is F 4.5-.6.7 which is pretty low light.
>
> Could anyone comment on just how restricted the lens would be shooting
> at 600mm.
>
> Using the 400mm on our analog Canon in Africa, has been working pretty
> well. The results have been ok for our armature photography skills and
> taste. .
>
> But, I was wondering that with the 1.5x conversion and the low F stops,
> shooting with 400m converted to 600m would make shooting with this lens
> hard to do, like very obviously too low a light conditions at sunset or
> early sunrise.
>
> Daytime should be ok?
>
> Thanks, Jon
>
Anonymous
April 19, 2005 6:05:39 PM

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

scubatv wrote:
>
> If you put a 400mm analog lens on a digital SLR camera, you will have
> around a 600mm lens.
>
> Our 400mm lens is F 4.5-.6.7 which is pretty low light.
>
> Could anyone comment on just how restricted the lens would be shooting
> at 600mm.
>
> Using the 400mm on our analog Canon in Africa, has been working pretty
> well. The results have been ok for our armature photography skills and
> taste. .
>
> But, I was wondering that with the 1.5x conversion and the low F stops,
> shooting with 400m converted to 600m would make shooting with this lens
> hard to do, like very obviously too low a light conditions at sunset or
> early sunrise.
>
> Daytime should be ok?
>
> Thanks, Jon

The 400mm lens remains a 400mm lens, so the same light/aperture/shutter
speed parameters remain. However, the 400mm lens on the digital body
has the same *angle of view* as a 600mm lens would have on a film body
(and the 1/focal-length rule of thumb becomes the 1/(focal-length * 1.5)
rule of thumb.)

-Dave
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Anonymous
April 20, 2005 1:09:57 AM

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

> If you put a 400mm analog lens on a digital SLR camera, you will have
> around a 600mm lens.
>
> Our 400mm lens is F 4.5-.6.7 which is pretty low light.
>
> Could anyone comment on just how restricted the lens would be shooting
> at 600mm.

The F values are the ratio of lens length to aperture size. The amount of
light transmitted by the lens is directly related to this ratio and it
doesn't change just because the back focus is longer or shorter to
accommodate different size film/sensors.

--
Mark Lauter

Photos, Ideas & Opinions
http://www.marklauter.com
April 20, 2005 1:22:53 AM

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

"scubatv" <scubatv@yahoo.com> wrote in message
news:1113939091.767507.13860@l41g2000cwc.googlegroups.com...
> If you put a 400mm analog lens on a digital SLR camera, you will have
> around a 600mm lens.
No, your lens now shows an image which has the angle of view of a 600 mm
lens.
>
> Our 400mm lens is F 4.5-.6.7 which is pretty low light.
>
> Could anyone comment on just how restricted the lens would be shooting
> at 600mm.
No more restricted than it is on a film camera, except you don't see as much
of the scene. By the way, the reduced image size has the advantage of using
the sharper part of the circle of illumination of the lens. It might result
in a sharper image on the digital camera.
>
> Using the 400mm on our analog Canon in Africa, has been working pretty
> well. The results have been ok for our armature photography skills and
> taste. .
>
> But, I was wondering that with the 1.5x conversion and the low F stops,
> shooting with 400m converted to 600m would make shooting with this lens
> hard to do, like very obviously too low a light conditions at sunset or
> early sunrise.
No the changed angle of view has no influence on the exposure.
>
> Daytime should be ok?
As good as it is on the film camera.
Jim
>
> Thanks, Jon
>
April 20, 2005 1:55:03 AM

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

"Mark Lauter" <available_upon_request@just_ask_in_a_post.com> wrote in
message news:Fse9e.7422$716.6370@tornado.tampabay.rr.com...
>> If you put a 400mm analog lens on a digital SLR camera, you will have
>> around a 600mm lens.
>>
>> Our 400mm lens is F 4.5-.6.7 which is pretty low light.
>>
>> Could anyone comment on just how restricted the lens would be shooting
>> at 600mm.
>
> The F values are the ratio of lens length to aperture size. The amount of
> light transmitted by the lens is directly related to this ratio and it
> doesn't change just because the back focus is longer or shorter to
> accommodate different size film/sensors.
>
> --
> Mark Lauter
>
> Photos, Ideas & Opinions
> http://www.marklauter.com
>
The "Back Focus" has not changed.

The only thing that has changed is that the Sensor is smaller than a 35mm
Film Frame. It is placed the same distance from the Lens Flange as a Film
would be. The smaller sensor only "Sees" the central portion of the Image
projected by the lens.

If this distance was not maintained Infinity Focus would be out.

Roy G
Anonymous
April 20, 2005 4:43:04 PM

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

In message <1113939091.767507.13860@l41g2000cwc.googlegroups.com>,
"scubatv" <scubatv@yahoo.com> wrote:

>If you put a 400mm analog lens on a digital SLR camera, you will have
>around a 600mm lens.

The more correct way of saying this is that it has a field of view
equivalent to 600mm on a 35mm camera. It is still, and always will be,
a 400mm lens. If you start calling it 600mm, someone is going to come
along, and multiply it again to 900mm.

>Our 400mm lens is F 4.5-.6.7 which is pretty low light.

That's pretty dark for deep woods, and dusk and dawn, but the high ISOs
on the Canon DSLRs work pretty well. Get out there and try; you're the
only one who can judge if it's worth doing; you set the quality
standard. What I do when light is getting low, is to set the camera to
the slowest shutter speed in Tv mode that will freeze the action and the
shaking, RAW, and ISO 1600 with +1 EC. That represents an exposure
index of (ISO) 800, and if there is enough light, I get a nice "800"
exposure with hardly any noise. If the light is too low, the camera
will fail to achieve +1 EC, and I will have an ISO 1600 shot, or even a
higher exposure index, which will have to be pushed in the RAW
converter. Sometimes even images that are still dark, even with the
maximum push in the RAW converter, can look usable if you push them
further in the image editor with the Levels tool, but they will look
best if you convert to an image mode like Lab or HSV, and blur
everything but the luminance channel, and then, if necessary, downsample
the image for noise-less display.

>Could anyone comment on just how restricted the lens would be shooting
>at 600mm.
>
>Using the 400mm on our analog Canon in Africa, has been working pretty
>well. The results have been ok for our armature photography skills and
>taste. .

If it works fine for film, then you should be OK with the digital.
Canon DSLRs outperform 35mm film at high ISOs.

>But, I was wondering that with the 1.5x conversion and the low F stops,
>shooting with 400m converted to 600m would make shooting with this lens
>hard to do, like very obviously too low a light conditions at sunset or
>early sunrise.
>
>Daytime should be ok?

Exposure and lighting issues should be the same as the film; the digital
sensor you have is merely smaller than a 35mm frame, and works like a
crop of one.

You will, however, have a shorter maximum shutter time, assuming that
the output will be viewed at the same size as the full 35mm-frame image,
since any blur do to camera motion will be 1.5x as large or long.
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
Anonymous
April 28, 2005 11:44:46 AM

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

Ok, I might have made a boo boo here.

After talking to Canon, the tech said, for wildlife photography, if you
are not interested in speed, any card will do.

Any card.

So, at egghead.com, I bought 2 Kingston 1gb CF/1024. Their lowest
quality/rated card for $113. not including a $30 rebate.
..
If I'm reading the charts right, it will take 2 seconds to write a raw
file to this card. That will certainly create a data bottle neck,
correct?

How long will I have to wait to take pictures between shots?

Sorry, for being so lame, I'm on the video side of photography and
these numbers don't seem to penetrate well.

Thanks,
Jon
!