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05-14-2007, 08:27 AM   #1
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Question about the DA 50-200mm

This lens says it works for digital only, but if you hypothetically could put it on a film body, would it work like a 75-300 film equiv. on a digital body or because it's digital only would it look like 50-200?

I don't get how the designed for digital stuff works, I guess.

05-14-2007, 09:02 AM   #2
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There are a bunch of different issues here. First of all, the Pentax digital sensor is smaller than the 35mm film. When a lens says "digital only'" it means that it was designed to fit the smaller digital sensor, if you could put it on a film camera the chances are that there would be severe vignetting...you'd get a round image with the corners cut off. The second problem is that the DA 50-200mm does not have an aperture ring. There is no way to manually change aperture. I don't know if the electronics of the Pentax film cameras is the same, it's possible that the cameras that support automatic aperture will be able to operate the diaphragm of the 50-200, does anybody out there know for sure? Otherwise you would have to use the 50-200 wide open only, and it's not terribly great wide open, IMHO.
Thirdly you have it backwards. A 50-200 digital lens would have the FOV of a 35-135 lens on a film camera, (actually 33.333-133.33) this is due to the vignetting problem I first mentioned.

NaCl(hope that helps)H2O
05-14-2007, 10:39 AM   #3
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The DA lenses will not work on any film SLR that pentax produced (I have not checked in to their latest models, but I haven't seen any material that supports the idea of a DA lens on a film body.)... A have a ZX30, and it won't even work with a manual lens without an "A" position aperature ring.
05-14-2007, 11:25 AM   #4
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As long as the film camera supports P mode (auto-aperture), you'll be able to use DA lenses. However, as Buschmaster said, you'll get severe vignetting unless you're close to the 200mm setting.


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05-14-2007, 11:43 AM   #5
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QuoteOriginally posted by NaClH2O Quote
Thirdly you have it backwards. A 50-200 digital lens would have the FOV of a 35-135 lens on a film camera, (actually 33.333-133.33) this is due to the vignetting problem I first mentioned.

I think though that this is not quite right. The 50-200 would have the FOV on film of a 50-200 on 35mm. Focal length is focal length. What 35mm film users see as a 50mm would be seen using this lens on their 35mm film camera - with some dark corners and such. What we see thru our digital SLR is what the 35mm film user sees when he puts his 75mm on the camera.
05-14-2007, 02:19 PM   #6
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Here is an example

DA 18-55 on a Pentax SFXn (circa 1989) taken at 18mm.

As Mo mentioned, the lens should work on any Pentax camera supporting control of the aperture from the body even if its only program mode. So Super A onwards in theory. I did find that I couldn't get the auto focus to work with the SFXn but didn't bother investigating. I've also used on pre "A" bodies where it just shoots at one aperture.

At the 55mm end of the range this lens shows little or no vignetting but I was only interested in having an 18mm wide angle on film which is novel for me.

cheers

Greg
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05-14-2007, 08:32 PM   #7
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QuoteOriginally posted by ccallana Quote
I think though that this is not quite right. The 50-200 would have the FOV on film of a 50-200 on 35mm. Focal length is focal length. What 35mm film users see as a 50mm would be seen using this lens on their 35mm film camera - with some dark corners and such. What we see thru our digital SLR is what the 35mm film user sees when he puts his 75mm on the camera.
Thanks, I think that's what I was asking. I guess I even confused myself!

I wouldn't be trying to put it on a film SLR, but I was just wondering. So the 50-200 is basically like a 75-300 lens would be on a film SLR, that's what I was trying to figure out.
05-14-2007, 08:36 PM   #8
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QuoteOriginally posted by Buschmaster Quote
So the 50-200 is basically like a 75-300 lens would be on a film SLR, that's what I was trying to figure out.
Yep, that's it. That's what 1.5x crop factor refers to.

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