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Sony 85mm F2.8 SAM Prime Comparison to Zooms

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QuietOC View Drop Down
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Post Options Post Options   Quote QuietOC Quote  Post ReplyReply Direct Link To This Post Topic: Sony 85mm F2.8 SAM Prime Comparison to Zooms
    Posted: 23 June 2016 at 23:04
My second copy of the Sony AF 85 mm F2.8 SAM arrived in today, so I ran it through a comparison with a bunch of zooms at 85mm using the APS-C A58 and a test chart (so fairly close focus). These are all manually focused with magnification and peaking. All at f/4 or as close to f/4 as they could get.

Center Sharpness


Extreme Top Left Corner


Bottom Right Corner


The DT zooms have crazy center sharpness, especially the 18-135. The DT 55-300 SAM beats the 85mm F2.8 with much better CA control.

Edited by QuietOC - 10 September 2016 at 20:15
Sony A7RIV LA-EA5
Pentax Q7 5-15 15-45/2.8 8.5/1.9 11.5/9
 



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LAbernethy View Drop Down
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Post Options Post Options   Quote LAbernethy Quote  Post ReplyReply Direct Link To This Post Posted: 24 June 2016 at 01:36
an interesting comparison. how did the two Sony AF 85 mm F2.8 SAM lenses stack up against each other? have you done the same lens comparison on another body? as nutty as it seems I've found that different lenses preform differently on other bodies.
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Post Options Post Options   Quote QuietOC Quote  Post ReplyReply Direct Link To This Post Posted: 24 June 2016 at 01:50
Both 85/2.8s are there. They seem to perform very similarly--identical as far as my ability to test them.

I have an A65, and have compared a few lenses with both bodies. The A58 is the better body for lens testing.
Sony A7RIV LA-EA5
Pentax Q7 5-15 15-45/2.8 8.5/1.9 11.5/9
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Post Options Post Options   Quote LAbernethy Quote  Post ReplyReply Direct Link To This Post Posted: 24 June 2016 at 02:09
if the two frames i'm looking are correct (two center top row) the left hand one is the better by quite a bit.
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Post Options Post Options   Quote QuietOC Quote  Post ReplyReply Direct Link To This Post Posted: 24 June 2016 at 02:48
The two 85/2.8s are focused at different points. I can tell by the axial CA. The left one is showing more magenta in the center. Magenta fringing showing in the center tends to look sharper than cyan fringing showing. The focus plane is a bit curved so that one also ends up with more in-focus corners.
Sony A7RIV LA-EA5
Pentax Q7 5-15 15-45/2.8 8.5/1.9 11.5/9
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Post Options Post Options   Quote Miranda F Quote  Post ReplyReply Direct Link To This Post Posted: 24 June 2016 at 07:21
Interesting!
It seems to confirm my experience that the dt zooms are extremely sharp in the centre when you can get them focussed well enough, even near full aperture, though focussing them accurately enough in real life is often non-trivial (the A58 AF certainly isn't good enough).
The corners look good too on my phone screen, how do they look to you?
Miranda F & Sensorex, Sony A7Rii, A58, Nex-6, Dynax 4, 5, 60, 500si/600si/700si/800si, various Sony & Minolta lenses, several Tamrons, lots of MF primes and *far* too many old film cameras ...
 



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Post Options Post Options   Quote QuietOC Quote  Post ReplyReply Direct Link To This Post Posted: 24 June 2016 at 11:34
The more corrected lenses like the 18-135 and 55-300 are sharp in the center even with the focus off quite a bit. The ones with axial CA there is basically a choice between minimizing fringing or maximizing sharpness or somepoint between those. They just can't get very sharp.

A flat focus plane is not important for most photos.
Sony A7RIV LA-EA5
Pentax Q7 5-15 15-45/2.8 8.5/1.9 11.5/9
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Post Options Post Options   Quote thornburg Quote  Post ReplyReply Direct Link To This Post Posted: 24 June 2016 at 13:20
Did you take several shots with each lens and only use the best one?
Did you use a tripod?

It seems to me that some of your results are so blurry that there was either a flaw in the shot (camera shake, missed focus, etc), or you have a very poor copy of that lens.

For example, my first copy of the 24-85 was much sharper than your results here.

I haven't tested my current copy to the same extent, as I rarely use it.
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Post Options Post Options   Quote QuietOC Quote  Post ReplyReply Direct Link To This Post Posted: 24 June 2016 at 14:05
I used a tripod. Steady Shot off. I frame the chart with the prime and then keep the tripod in that location for all the other lenses. I focused the 55-200 and 55-300 twice which is why there are two photos of those.

These are all very good copies of these lenses. Well the 28-135 is pretty sad looking and doesn't focus at infinity right now. Remember the zooms here are all wide-open. I just tried another copy of the original 35-105 that was worse than this copy. I am surprised by how badly that lens did in this comparison. The chart might be a little closer than the MFD of the 35-105. That is not an issue for the 24-85 though.

I believe this is the sharpest 24-85 I've had. It is the third one. Performance at the 85 mm end is not its strength. I know the 28-105s were a lot sharper at 85 mm than the previous copies of the 24-85. The 85 mm end of the 24-85 does not match the field-of-view of the 85/2.8 here either. The 85/2.8 is a bit longer than 85 mm at this distance, and the 24-85 is shorter than 85 mm at this distance.

I do a lot of these comparisons. This isn't odd performance for the 24-85. It would look a lot better compared over its entire range with some other normal zooms instead of trying to match a prime and the telephoto zooms at 85 mm.
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Post Options Post Options   Quote thornburg Quote  Post ReplyReply Direct Link To This Post Posted: 24 June 2016 at 14:27
Originally posted by QuietOC QuietOC wrote:

I do a lot of these comparisons. This isn't odd performance for the 24-85. It would look a lot better compared over its entire range with some other normal zooms instead of trying to match a prime and the telephoto zooms at 85 mm.


Maybe I had a much better than average copy.

I mostly shot with it at 85, which is was my original rational for letting it go -- since I was only using the long end, other zooms, like the 35-105, made more sense (that, and a forum member made me a very good offer on it).
Sony a3000, a6000, a57, a99 - Sony E 16-50, 28/2 | Vivitar 13, 85 | Minolta 24, 28-105, 35-105, 50/1.7, 75-300 | Tokina 28-70/2.6-2.8 | Sigma 70/2.8 Macro | Tamron 70-200/2.8 | Celestron 1000/11
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Post Options Post Options   Quote craig66 Quote  Post ReplyReply Direct Link To This Post Posted: 24 June 2016 at 15:32
My copy of the 35-105 (orig) is sharper in the corners than the 55-300 DT at wider apertures. It also has much less off-axis astigmatism. The 55-300 is sharper in the centre but not by a large margin.

My only other DT zoom - the 16-50 f2.8 SSM - is an astigmatism monster at the long end. It also has considerable focus shift at the long end.

The problem with lens tests is the sample variation.
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Post Options Post Options   Quote addy landzaat Quote  Post ReplyReply Direct Link To This Post Posted: 24 June 2016 at 15:58
At what focus distance? The more experienced I get I find that focus distance is very important. Some lenses are great at longer distances but lousy at MFD and the other way round.
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Post Options Post Options   Quote QuietOC Quote  Post ReplyReply Direct Link To This Post Posted: 24 June 2016 at 16:37
This was pretty close. As I said above it was near the minimum focus distance of the 1985 Minolta AF 35-105 F3.5-5.6 ~1.5m.

The distance might matter, but I have gotten similar results at greater distances too. I've done some comparisons recently outdoors with a brick wall. I did a comparison last year with a large horse statue.

My main goal here was just to see if the new 85/2.8 was any better than the old one, and the answer is, no.
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Post Options Post Options   Quote addy landzaat Quote  Post ReplyReply Direct Link To This Post Posted: 24 June 2016 at 17:36
On other lenses there is a significant difference between MFD, Mid distances and infinity.
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