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Vivitar Series 1 24-48mm f/3.8 tests
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PostPosted: Wed Nov 25, 2009 4:20 am    Post subject: Vivitar Series 1 24-48mm f/3.8 tests Reply with quote

Okay, as promised, I shot some test pics yesterday to evaluate my Vivitar Series 1 24-48mm f/3.8 that I bought about a month ago. It's in Canon FD mount, so previously I was only able to evaluate it shooting film. Unfortunately, the best film I had available for the evaluations was some ISO 200, which is too grainy to evaluate lens sharpness. About a week ago, I decided to buy a FD-EOS adapter with the glass element since I've seen some reports that indicate that one can achieve good results with it. So, I've used this adapter with the lens and my EOS DSLR for the evaluation. I've found that the adapter works very well with most lenses once they are stopped down to f/4 or so. Wider than that, there is quite a bit of flare.

This adapter also acts as a mild teleconverter, providing about 1.25x magnification. So, with the 1.6x crop factor added to the adapter's magnification factor, the focal length of the lens is about doubled. So this means that my tests are only meaningful, in terms of sharpness, when observing center sharpness, since the corners when used with an FF camera are not even close to being within the field of view with my setup.

Flare caused by the adapter with this lens wide open is noticeable, but not too bad, since its max aperture is only f/3.8. The following close-up photos were taken at f/3.8 and f/8. I used a small amount of contrast enhancement to remove a slight bit of hazy softness caused by the flare at f/3.8. No sharpness routines were used.

The photos are boring, but I'm shooting for detail, not visual interest. The subject is a storage barn in our backyard. The first two photos were taken from about 10 meters distance from the barn.

24mm @ f/8

48mm @ f/8

24mm @ f/3.8

24mm @ f/8

48mm @ f/3.8

48mm @ f/8

The photos are actually sharper than they seem to indicate. I need to do some 100% crops to show this. Too late to mess with it tonight. Maybe I'll post some tomorrow.

Last edited by cooltouch on Wed Nov 25, 2009 8:22 am; edited 1 time in total

PostPosted: Wed Nov 25, 2009 7:01 am    Post subject: Reply with quote

Looks a very usable lens to me! Not bad for an old zoom is it.

PostPosted: Wed Nov 25, 2009 6:48 pm    Post subject: Reply with quote

It would be better to test the lens without the adapter?

PostPosted: Wed Nov 25, 2009 7:03 pm    Post subject: Reply with quote

Yes, it would. But I don't own a DLSR that I can use it on to test it using digital format. I've already tested it using Kodak Gold ISO 200, and the grain clumps up before the resolution limit is reached. Actually, I've found with this lens and all my other FD-mount lenses, that center sharpness is still very high. So, I don't think it has much of an effect in that regard.

I should probably get a glass-less adapter also. The lenses will be of limited usefulness, but I can still do accurate resolution tests with them.

PostPosted: Wed Nov 25, 2009 7:35 pm    Post subject: Reply with quote

Okay, here are some 100% crops of the above close-ups. It was late afternoon and I was losing light. I was too lazy to drag out a tripod, so I bumped up the ISO instead. The pics were taken at ISO 400, and the noise is pretty obvious at 100%.

@ 24mm f/3.8

@ 24mm f/8

@ 48mm f/3.8

@ 48mm f/8

There is a noticeable difference in sharpness at 48mm between the two pictures. I think this is most likely due to human error than the lens or the adapter. I probably just missed on the focus slightly.

Here are 100% crops of the full shots of the barn. The point of focus for both images was the blue-and white porcelain flower pot.

@ 24mm f/8

@ 48mm f/8

Overall, I would rate the picture quality of this lens as 'good.' Not great, but a solid, good performer. To be most accurate, however, will require that I use some very fine grain slide film or buy an adapter with no glass for my EOS DSLR.