buggz Posted September 24, 2015 Share Posted September 24, 2015 Hello everyone,I've been playing with my Kowa B&H 2X on my 5DMkII via the excellent REDSTAN clamp.I'm currently using my Contax/Yashica Zeiss 100/f2.I notice that a "regular" 5DMkII still .CR2 RAW file size is:Image Width : 5616Image Height : 3744So, to desqueeze this, I have simply been doubling the width to: 11232However, from the following image, I see that the Kowa B&H isn't actually 2xI have also read that this is true of all anamorphic lenses?Are EACH individual lenses different, or are ALL the Kowa B&H have the same aspect ratio?How would I find this information?I have also read that one can draw circles, and figure out the correct ratio?Does it matter how close the focus is to the target?Anyone have a "Workflow" to calculate the ascept ratio of a lens?I'm guessing there isn't anyway to measure it?oh, and the image...Was testing the flaring *8^)Notice the Sun isn't circular. Quote Link to comment Share on other sites More sharing options...
ken Posted September 24, 2015 Share Posted September 24, 2015 Usually, I think above 10m can be treated as 2x. Closer focus will reduce the ratio. Closest 5f/1.5m is about 1.85x, IMO. Also, center part is less ratio then left/right edge. There is always some distortion. Quote Link to comment Share on other sites More sharing options...
Blake.H Posted September 24, 2015 Share Posted September 24, 2015 Best to just photograph a perfect circle that has horizontal and vertical lines intersecting at the middle of it from various distances away. Then unsqueeze at say 1.8x, 1.9x and 2x and compare until you see a perfectly round circle, that will be the squeeze factor.I have an Isco Ultra Star that is labelled as 2x but after testing it this way myself I found it to be 1.8x. Flynn 1 Quote Link to comment Share on other sites More sharing options...
ken Posted September 24, 2015 Share Posted September 24, 2015 Best to just photograph a perfect circle that has horizontal and vertical lines intersecting at the middle of it from various distances away. Then unsqueeze at say 1.8x, 1.9x and 2x and compare until you see a perfectly round circle, that will be the squeeze factor.I have an Isco Ultra Star that is labelled as 2x but after testing it this way myself I found it to be 1.8x.To me, all 2x lenses are always 2x if focus distance far enough. I think the reason is mounted, not closed enough. Here is an sample taken by ISCO's integrated projector lens.https://flic.kr/p/qqGzkQ Quote Link to comment Share on other sites More sharing options...
buggz Posted September 26, 2015 Author Share Posted September 26, 2015 Thanks for the replies!I am reading a reply on another forum, that this is normal, for the Sun NOT to be a perfect circle?I would have thought you could desqueeze to normal proportions?Is this possible, or not?I also read from Ken's reply here, that the horizontal field is not linear.This makes sense.Also from from another forum, I see a reply suggesting that the distance could be too far from the anamorphic lens, and the taking lens.However, I am only using the awesome REDSTAN calmp, and one stepdown ring between the two lenses.I could see this being a problem if I was using multiple rings...Many thanks for the valuable information replies!I will will continue to refine my experiments. Quote Link to comment Share on other sites More sharing options...
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