110 deg of view: Hologon vs Distagon with Sony ILCE-7 (A7)

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110 deg of view: Hologon vs Distagon with Sony ILCE-7 (A7)

By Wojciech Zielinski

Greetings,
I finally took series of comparison shots with Hologon 8/16mm CG and Distagon 2.8/15 ZE. As Dr Nasse published and elaborated by measurements (with courtesy of Horst Wittmann), Hologon has very huge resolution drops at the edge of full frame. With APS-C there wasn't such a problem, especially without this severity (at Sony NEX-7). Telecentric Distagon lens hasn't any problem to image to Sony A7's sensor with very pleasant outcome.

http://www.zeissimages.com/gallery/1155/U1155I1388588774.SEQ.0.jpg
Carl Zeiss Hologon 8/16 CG

http://www.zeissimages.com/gallery/1155/U1155I1388588935.SEQ.0.jpg
Carl Zeiss Distagon 2.8/15 ZE at f/2.8

http://www.zeissimages.com/gallery/1155/U1155I1388595142.SEQ.0.jpg
Crop 200% of photo shows bands (with Carl Zeiss Hologon 8/16 CG)

One more interesting observation are horizontal strong bands (lines) in the extreme regions of images, which was taken with Hologon lens. They are symmetrically distributed in extreme upper and extreme lower part of photo, horizontally they are best visible at 1/3 and 2/3 of photo's length but they are available at full width of image. They forms regular, repeated pattern, which upper and lower group of lines are mirrored to each other. Even magenta colour of upper lines are complemented with green colour of lower bands. Upper bands, around text label, are better visible, because they are projected at quite bright, plain (solid color) background. If I moved the lens radially, those lines didn't change position (rotation). So this effect isn't connected with any not radial properties of lens (like scratches on lens's surfaces).

Do You have any idea if those bands are physic devoted (like some of optical effect, eg. diffraction) or it could be some post-production (like eg. electronic or firmware related problem) error?

I even thought about some sensor malfunction but as far as I tested it, those bands are not visible with any SLR lenses, even those with very short front focal lengths.

Thanks for any advices or ideas.
best regards, WZ.

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Replies

Reply from Wojciech Zielinski on 01-11-14 10:42 PM

Greetings Filipe :)
Thanks for making some research and finding for me those information. I am a little sceptical about involving Phase-detect sensor with dotted problem. Those special pixels are located in center of image and they are not available at extreme part of image but those mysterious bands are visible there too.
About shutter problem there is no additional information if author of this information has used a modified version of Hologon lens or just a raw one. As it was described by few sources I have cut out sensor-side 'ears' of lens. If there should be any problem with totally plane shutter, it should hit most inward located part of last lens element, which is most centre part of the lens in radial point of view. But at the center of image, there isn't any signs of bands. If You even assume that whole exit part of lens has been slashed by shutter, those sign of slapping should be equally distributed over the whole image plate and as far as I see it, they aren't equally distributed.

I believe that I have already lost obstinacy to use my Hologon lens with my A7 camera. I will try to follow up history of use to this lens but I will try to shoot with another my lens, Distagon 2.8/15mm ZE. It doesn't bother me it is big and heavy lens, unless it is Carl Zeiss lens :)
Best regards, WZ.

Reply from Filipe BrandÃo on 01-5-14 4:07 PM

Hello,
I read a report here: http://www.flickr.com/photos/dierktopp/11015638594/in/set-72157637947047035
He basically says that his hologon blocked the travel of the shutter on the A7r. Either there is a difference between the A7r and the A7 regarding the position of the shutter or your are making something different that's preventing the problem.
In any case I was wondering if the shutter could be the cause of the dotted lines.
There is yet another possibility. It seems the A7 has on sensor phase detection AF, while the A7r does not. Those dotted lines could be the sensor photo sites dedicated to AF. If this was true, then you shouldn't be seeing the dotted lines on the center of the frame, since the light would be hitting the sensor at a less acute angles. Just throwing some ideas. Hope it helps.
cheers,
Filipe

Reply from Wojciech Zielinski on 01-4-14 5:06 AM

Greetings Filipeb :)
In camera lens correction was applied only in module 'Peripheral Shading'. 'Chromatic Aberration' and 'Distortion' was untouched (it was left at '0' correction level). Even without in camera lens correction application ,those bands were visible too. Hologon has great flatness of image, it doesn't need any distortion correction.
Purple holos (magenta shift) are natural with Hologon lens, it was also visible with APS-C sensor :) It was expected, but those bands not :( I am still curious. I made multiple images already with Carl Zeiss Hologon lens and Sony A7. In all of conditions, all photos has those bands available. Do You have any ideas?
Best regards, WZ.

Reply from Filipe BrandÃo on 01-3-14 4:15 AM

Hello,
Thank you for taking the time to make these comparisons and share them.
Do these bands show up on the image before the image is distortion corrected?

I noticed some purple halos on the sky in the Hologon image. Considering the lens design it is very likely that it is caused by the acute angles of light hitting the sensor.

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