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Next PZ lens test report: Zeiss ZF Distagon T* 35mm f/2.0 (FX) - Printable Version

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Next PZ lens test report: Zeiss ZF Distagon T* 35mm f/2.0 (FX) - AT75 - 02-24-2011

so I'm sure this is not a "tester error" or "measurement method", as "individual approach" or a human factor in the CA measurements could be really misleading.



what is it, then? <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='Smile' />) why such a difference of the same lens, giving such different results on the sensors, that are more or less close in resolution. that looks very-very strange, but interesting <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='Smile' />))



could it be a sensor behaviour? microlenses?


Next PZ lens test report: Zeiss ZF Distagon T* 35mm f/2.0 (FX) - mst - 02-24-2011

[quote name='Brightcolours' timestamp='1298547691' post='6316']

In my opinion, it is the different tester doing the measurements. It is quite hard to measure CA "amount".

[/quote]



Sorry to disappoint you but it's actually quite simple. Almost a byproduct of the MTF analysis in Imatest.



-- Markus


Next PZ lens test report: Zeiss ZF Distagon T* 35mm f/2.0 (FX) - mst - 02-24-2011

[quote name='AT75' timestamp='1298571737' post='6326']

could it be a sensor behaviour? microlenses?

[/quote]



Maybe. But honestly I can only speculate, too. Could also be the different RAW converters we use, or many other things. Or an ugly mixture of all of it <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='Wink' />



-- Markus


Next PZ lens test report: Zeiss ZF Distagon T* 35mm f/2.0 (FX) - AT75 - 02-24-2011

Markus, do you shoot the CA tests in RAW first and then process them in C1?


Next PZ lens test report: Zeiss ZF Distagon T* 35mm f/2.0 (FX) - Brightcolours - 02-24-2011

It most certainly can NOT be the microlenses, it is impossible for those to increase or decrease CA.


Next PZ lens test report: Zeiss ZF Distagon T* 35mm f/2.0 (FX) - mst - 02-24-2011

[quote name='AT75' timestamp='1298575762' post='6330']

Markus, do you shoot the CA tests in RAW first and then process them in C1?

[/quote]



The same RAW images are used for MTF and CA. They are converted by RAW Developer (a Mac only tool) and then fed to Imatest. There is no CA correction happening.



-- Markus


Next PZ lens test report: Zeiss ZF Distagon T* 35mm f/2.0 (FX) - AT75 - 02-24-2011

[quote name='mst' timestamp='1298582386' post='6336']

The same RAW images are used for MTF and CA. They are converted by RAW Developer (a Mac only tool) and then fed to Imatest. There is no CA correction happening.



-- Markus

[/quote]

I see, thanks. And the Canon conversion (done by Klaus?) - does it include the same procedures and software?


Next PZ lens test report: Zeiss ZF Distagon T* 35mm f/2.0 (FX) - mst - 02-24-2011

Same procedure, but different software. ACR, to my knowledge.



-- Markus


Next PZ lens test report: Zeiss ZF Distagon T* 35mm f/2.0 (FX) - AT75 - 02-25-2011

[quote name='mst' timestamp='1298583378' post='6339']

Same procedure, but different software. ACR, to my knowledge.



-- Markus

[/quote]

I've made a small test to check, if the Raw Developer shows more CAs on the same file, than the ACR



And see no significant difference to speak of.



So, if we have the same lens, same shooting distance, same testchart, (also same lightning, I hope?) and same Imatest version, it is unlikely to find twice as much CAs between these 2 different RAW converters (as we see sometimes in the tests of ZF lenses). So, if the conditions are the same between your shots and Klaus', it really could be a sort of sensor difference.



If they are not the same... I think there should be some more unity in the measurements <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='Smile' />)))


Next PZ lens test report: Zeiss ZF Distagon T* 35mm f/2.0 (FX) - Brightcolours - 02-25-2011

[quote name='AT75' timestamp='1298616211' post='6345']

I've made a small test to check, if the Raw Developer shows more CAs on the same file, than the ACR



And see no significant difference to speak of.



So, if we have the same lens, same shooting distance, same testchart, (also same lightning, I hope?) and same Imatest version, it is unlikely to find twice as much CAs between these 2 different RAW converters (as we see sometimes in the tests of ZF lenses). So, if the conditions are the same between your shots and Klaus', it really could be a sort of sensor difference.



If they are not the same... I think there should be some more unity in the measurements <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='Smile' />)))

[/quote]

You must have littel understanding of LaCA, if you think the sensor or its microlenses can affect the amount. The D3x has a vertical resolution of 4032 pixels, the 5D mk II has a vertical resolution of 3744 pixels.

The resolution of the sensors is the only thing that can influence the LoCA measurements (if done correctly).



The D3x should have a higher CA value with the same lens of 100 / 3744 * 4032 = 108%.



It is impossible for microlenses to make for instance the whole red projection bigger (that is what LaCA is about, it is measuring how the different colours or wavelengths of light get bent more or less through the optics of the camera's lens, producing some colours to have a bigger or smaller image projected onto the sensor). Microlenses can only affect the pixel they reside above, they can NOT direct light of only a certain wavelength uniformly to neighbouring pixels.



Even a difference of AA filter strength should not affect CA measurements. Most probably, the software doing the measuring is not very reliable / not very good at it / not really measuring CA as we know it.