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aspect ratio help


buggz

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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                       : 5616
Image Height                      : 3744
So, to desqueeze this, I have simply been doubling the width to: 11232
However, from the following image, I see that the Kowa B&H isn't actually 2x
I 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.

 

_MG_6870-KowaBH-CYZ100f2-resized.jpg

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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.

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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

 

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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.

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