Photoclubalpha

I thought I'd post a couple of shots comparing the Minolta 500mm reflex to the Tamron 70-300mm. They were taken under similar lighting even though they were taken on 2 different days. The Minolta has much better range, but is also softer than the Tamron. Also the Minolta is fixed f/8. The Tamron image was also shot using f/8. The Minolta had no CA while the Tamron had a very minimal amount of CA around the back of the deer and the antlers. LR easily took care of it. These shots have not been cropped but have had some minor adjustments in LR.

The first is the Minolta and the second is the Tamron.

100% crops Minolta first then the Tamron. The noise in the Minolta shot is at least partly to do with being shot at ISO 400 while the Tamron was ISO 100. Next time I do this I'm going to have to make sure the ISO settings are the same.

Okay, Hefay, I have to ask - why were there no shots of them hanging from the tree after you field dressed them?

Dusty

Well Dusty, it's like this. They always go on a ten day vacation during October.

I've never used the 500mm F8 it's a curious lens possibly a bit specialist for me. Which Tamron is this the newer USD version?

Yes it's the USD version.

I was interested to see your comparison, but don't feel that the deer you shot with the Minolta and posted at 1:1 is in focus. Looking at the whole frame, the plane of sharp focus is definitely behind the nearer animal that you also showed as a 1:1 crop, and possibly even slightly behind the other deer.

I turned down the chance to buy an example of the 500 mirror a few weeks ago, but am regretting it, because I think I'd make good use of it, so long as the AF works well.

I checked the image again and the whisker detail on the buck are similar to the hairs sticking off of the rear leg of the doe. The grass and sticks that are just beyond the doe seem sharper until you zoom in on them and then they are pretty much the same as the deer. So perhaps the center of the focus is closer to the second deer but the sharpness from the buck to weeds beyond the doe seem to be similar. Another thing to consider is that my tripod is not really sturdy enough for this lens camera combination. The weight is borderline and that is quite a long zoom. It is possible that there was some very slight camera jiggle or drifting during the shot. Also, it turns out that my Minolta lens has a slight amount of something that looks like spider webs or very fine lines on the mirror. I suppose it is fungus. YUCK! I wonder what affect that has on the IQ.

Oh drat...the dreaded fungus...I hate that stuff!!

I've just been doing a similar test -- comparing my Sony 500mm reflex with the Tamron 70-300mm on my A77. The reflex came out much sharper, but the Tamron at 300mm was fuzzy enough that I suspect I must have messed up somehow. I'm going to have to do some more careful testing with manual focus on a tripod with good light and clear calm air and not wearing gloves

Years ago I did a quick test of the 500mm reflex against the then new Sony 70-400mm G. They let me take the 70-400mm out of the camera shop and try a monopod shot of a church roof down the street. I tested them with my A77 and the shop's A99. The result was the same with both cameras. The 70-400mm at 400mm was getting a just discernible amount of extra detail if you examined the pixels very carefully.

I've been reading up on the technology of catadioptric camera lenses. The web seems curiously vague about this 500mm Minolta/Sony reflex. Is it a Schmidt-Cassegrain Newtonian with Mangin mirrors?

The Min-Sony 500mm is a hybrid. It has a more 'important' optical group than most mirror lenses and it's very much cata-di-optric not catoptic. The Tamron 500mm macro reflex I've bought recently is in a different class - never expected to use any mirror lens with the same contrast and sharpness.

David