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Author Topic: Is it possible for a lens to shoot better wide open than stopped to f8 ?  (Read 681 times)
One Frame at a Time
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« on: November 09, 2012, 05:13:00 PM »
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I just got an NEX 6 delivered with the 16 to 50 mm zoom.  I shot a few test images with the new lens and an older - cherry picked 18-55 from an NEX 5n.  

Initially, I thought the new lens was much better than the old one.  That thought faded as I compared images shot stopped down to f8.  The old lens had a significant improvement Stopped vs Wide Open.  The new lens was the reverse.  Stopped to f8 was slightly to noticeably worse than Wide??  Camera was set to auto focus and there are some frames that are off because of focus error.  But every shot at f8 with the new lens is worse than set to wide open, while every shot with the old 18-55 was better closed down. I shot both lenses at 18mm, 35, and 50mm.  Jpeg + RAW 

I"m too busy right now to figure out how to do 100% crops and post right now. I should not even be messing with them but hey, its a new toy!

 Thanks,  Paul
« Last Edit: November 09, 2012, 05:14:38 PM by One Frame at a Time » Logged
deejjjaaaa
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« Reply #1 on: November 09, 2012, 05:53:42 PM »
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probably... see how 18-55 was tested - certain focal length', center of the frame degraded being stopped down to f8

http://www.photozone.de/sony-alpha-aps-c-lens-tests/543-sony1855f3556nex?start=1

another test partially supports, partially contradicts

http://www.lenstip.com/293.4-Lens_review-Sony_E_18-55_mm_f_3.5-5.6_OSS_Image_resolution.html
« Last Edit: November 09, 2012, 06:00:22 PM by deejjjaaaa » Logged
Deep
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« Reply #2 on: November 10, 2012, 03:40:30 PM »
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Plenty of lenses are better wide open than at f8 (for example many, if not most, 4/3 lenses).  With some zooms, it depends on the focal length.  The very general pattern for many, many lenses is that they are best stopped down a little and deteriorate slightly from there.  No hard and fast rules though!  However, if you are seeing a drastic reduction in quality, I'd suggest there is something else happening (slower shutter speeds? a build problem with the particular lens).  F8 should be fine with those lenses.

Don
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Don
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« Reply #3 on: November 10, 2012, 05:55:22 PM »
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Thanks Guys,
I always thought stopping down a couple stops always improved sharpness.  Now I know otherwise.

Shot the test images on a tripod so I don't think shutter speed was in any way a factor (steady shot - off).  I have two copies of the new lens.  If the sun shines tomorrow I hope to make a comparison and see if one is a lemon.  Then I'll put the better one up against the 18-55.   One thing I noticed last night was the color rendering of the new lens is MUCH different.  Thought it might be a jpeg thing but its the same on the RAW images too.  The new lens is much warmer.  The old 18-55 is very noticeably cooler and a bit greener.  Did not realize that a lens could shift colors like that either? 
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