55mm f1.8 corners smeared on 6500

I've used a Zony 55mm happily with three full frame bodies, including the A7RII. It's very sharp in the center by f2.2, sharp over most of the frame by f4, and sharp even in the extreme corners by f5.6.

So when I got the a6500, I thought it would be a good option as a moderate telephoto. However, in my testing it stays smeary in the corners even at f5.6. (All four corners.)

I compared it to the Sigma 60 f2.8 using the exact same setup, and the Sigma just destroyed it. The Sigma is noticeably sharper in the corners at f2.8 than the 55mm at f4, sharper at f4 than the 55mm is at f5.6. Hmm.

Is there some physics I don't understand here? I know that high-density APSC sensors can put a strain on lenses. But this result seems extreme, considering that I'm only using the center of the 55mm image circle. One possibility is that there is some distance-related field curvature issue (I tested at a range of 3-4 feet).

Incidentally, my Zony 35mm f2.8 shows no such behavior. It's razor sharp on the a6500 starting wide open; a great little standard lens for this camera.

I bet this is pixeldensity magnifying lens flaws. To test this, take a photo with you A7rii in crop mode. Then take same picture with your APS-C camera and downsample in Photoshop to same pixel size as from your full frame crop mode.

I bet they look the same.

Well heck...this is not what I wanted to hear. I sold my 50 OSS knowing that I would be getting the 55 to match up with my a6500.

mixem227 said:

Well heck...this is not what I wanted to hear. I sold my 50 OSS knowing that I would be getting the 55 to match up with my a6500.

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I think you will not be disappointed - the 55/1.8 is very good indeed and there is more to image quality than ultimate corner sharpness wide open. I use both 55/1.8 and Batis 85 with excellent results on my A6300.

Besides, having that lens gives you an upgrade path to FF.

BBQue said:

mixem227 said:

Well heck...this is not what I wanted to hear. I sold my 50 OSS knowing that I would be getting the 55 to match up with my a6500.

Click to expand...

I think you will not be disappointed - the 55/1.8 is very good indeed and there is more to image quality than ultimate corner sharpness wide open. I use both 55/1.8 and Batis 85 with excellent results on my A6300.

Besides, having that lens gives you an upgrade path to FF.

Click to expand...

I have now tested the 50 OSS as well. On the a6500m at the distance tested (3-4 feet), It is noticeably sharper in the corners than my 55 Zony from f1.8 to f5.6. The Sigma 60 is better than either of them. Not what I expected.

However, all are good lenses; all will be fine at reasonable print sizes. And the Zony can do double duty with a full frame body.

I would note that this is NOT the same comparative result recorded by photozone on the NEX-7. JohnNEX has put the data together HERE: https://www.dpreview.com/forums/post/58672512

In the useful charts he assembled, the Sigma 60 does come out on top, but the 55 Zony has better results than the 50 OSS. I'm not sure what accounts for the discrepancy--the different camera sensor or copy variation. Possibly I have a weak copy of the 55mm, although it is great on full frame.

This YouTube video is relevant to the 50 vs 55 discussion:


Summary: A comparison is done with multiple shots and images are pixel peeped with almost no difference. My take is if you only have an a6000/6300/6500 and no a7 series camera you should stick with the cheaper 50 as the 55 provides no real gain in IQ.

BBQue said:

I bet this is pixeldensity magnifying lens flaws. To test this, take a photo with you A7rii in crop mode. Then take same picture with your APS-C camera and downsample in Photoshop to same pixel size as from your full frame crop mode.

I bet they look the same.

Click to expand...

You may be right. Although if I crop a full frame image to APSC size, I see no lack of sharpness in the cropped corners, at any magnification.

At the end of the day, comparing the 55 Zony, the Sigma 60 and the 50 OSS lenses on the same a6500 body resulted in a difference in corner sharpness. I believe this would only be noticeable, even in a large print, when corner sharpness is important (and at larger apertures).

I'd love to have somebody else do a similar comparison, if only to see if my 55 Zony is a weak copy. Tests at different distances would be useful, too. If I have time, I'll do some.

DragonPunch said:

This YouTube video is relevant to the 50 vs 55 discussion:

Summary: A comparison is done with multiple shots and images are pixel peeped with almost no difference. My take is if you only have an a6000/6300/6500 and no a7 series camera you should stick with the cheaper 50 as the 55 provides no real gain in IQ.

Click to expand...

Good link. If you look at some of the corner comparisons, especially after 10 minutes into the video, you see some slight advantage to the 50mm lens. Although at f8, there is virtually no difference.

Since you see it on the 6500 but not the a7, could the source be in-camera distortion correction?

missingendpoint said:

Since you see it on the 6500 but not the a7, could the source be in-camera distortion correction?

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Good thought, but in-camera correction was turned off.