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Archive 2016 · SEL3518 vs SEL5018 - Do I have a bad lens?
  
 
dills84
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p.1 #1 · p.1 #1 · SEL3518 vs SEL5018 - Do I have a bad lens?


Hey all... I've been pretty disappointed with my SEL3518 (Sony 35mm f1.8 OSS) sharpness wide open. However, I'm pretty happy with my SEL5018 (Sony 50mm f1.8 OSS) sharpness. I'm starting to wonder if I got a bad copy of the 35mm?

I decided to do some non-scientific tests in my kitchen. I printed the B&H test chart and took some shots with the 35mm and 50mm. I moved the 50mm back to get the composition nearly identical. The camera is my A6300 and it was mounted to a tripod and shot with a 2 second self timer. Camera settings were identical in manual mode.

If you look at this gallery I posted to google drive you can see that the 35mm is terribly soft wide open.

Is my copy bad? Or is the 35mm known to be super soft wide open? It's not terrible at 2.8 and above... but 1.8 is nearly useless. I have some adapted Canon FD glass that's sharper!

What do you think?

https://drive.google.com/drive/folders/0Bz0WeUKyeOS4c3MtZjNtemgzdkU



Oct 15, 2016 at 05:05 PM
mogul
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p.1 #2 · p.1 #2 · SEL3518 vs SEL5018 - Do I have a bad lens?


I have both lenses but never have tested them against a chart...off hand, I would say you may have a sub par lens.


Oct 15, 2016 at 06:34 PM
Princeps
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p.1 #3 · p.1 #3 · SEL3518 vs SEL5018 - Do I have a bad lens?


I have had both of them and didn't notice significant differences in their wide-open sharpness, both were very good.

At some point I tested 5 50s on a bookshelf (Canon EF 50 1.4, C/Y 50 1.4, OM 50 1.8, OM 50 3.5) and the Sony was the best at equivalent apertures. Never felt like the 35 was behind, felt like the same lens at a different FL.

I think you may have a bad copy or may be seeing field curvature, where was your focus point on those photos? Does it not get sharp in the corner if you focus *on that corner*?

I noticed the 35 did not play well with filters, showing flare, I think something about the concave front element.



Oct 16, 2016 at 12:05 AM
 

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dills84
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p.1 #4 · p.1 #4 · SEL3518 vs SEL5018 - Do I have a bad lens?


No filters andboth lenses were focused manually to the center of the test chart using magnification and peaking... I took several shots to make sure the focus was nailed. The 50 is plenty sharp for me... I really like it. But the 35 feels like mud on comparison! I might swing buy a local store to see if I can try a different copy.

Thanks for your input!

Princeps wrote:
I have had both of them and didn't notice significant differences in their wide-open sharpness, both were very good.

At some point I tested 5 50s on a bookshelf (Canon EF 50 1.4, C/Y 50 1.4, OM 50 1.8, OM 50 3.5) and the Sony was the best at equivalent apertures. Never felt like the 35 was behind, felt like the same lens at a different FL.

I think you may have a bad copy or may be seeing field curvature, where was your focus point on those photos? Does it not get sharp in the corner if you focus *on
...Show more



Oct 16, 2016 at 12:17 AM
stevei
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p.1 #5 · p.1 #5 · SEL3518 vs SEL5018 - Do I have a bad lens?


One thing I like to do is to shoot a subject at an angle, e.g. have your printed target on a table facing straight upwards, and then have the camera pointing down at it at approx 45 degrees. If you do that you can 100% rule out focusing as an issue, as you can see where the sharpest focus is, with it becoming progressively more blurred both in front of, and behind, where the sharpest focus is. If I do this with my recently purchased Sony 50/2.8 macro, for example, the point of sharpest focus on the left is much softer than the point of sharpest focus on the right, and I can see that the problem with the lens is that it is simply soft on the left, rather than it having a tilted plane of focus. If I tried to shoot a flat subject straight on, it would be hard to rule out misalignment of camera and subject as the cause of the softness on one side, and also it wouldn't be possible to differentiate between the cause being a tilted plane of focus, or it being soft at the point of sharpest focus, and I always like to be able to accurately report exactly what is wrong with a lens if I'm going to return it.


Oct 16, 2016 at 06:46 PM
dills84
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p.1 #6 · p.1 #6 · SEL3518 vs SEL5018 - Do I have a bad lens?


As an update... I ended up returning my SEL3518 and getting a new copy. The new copy is WAY sharper wide open. Pretty obvious that the other copy I had was flawed.


Oct 17, 2016 at 03:59 PM







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