Stage micrometer slide image

Just bought that first macro lens? Post here to get helpful feedback and answers to any questions you might have.

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Photosbykev
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Stage micrometer slide image

Post by Photosbykev »

Can someone just confirm my math is correct based on the image shown below please?

Image

This link is to an image which has been resized by exactly 50%

regards
Kev

rjlittlefield
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Post by rjlittlefield »

That all looks correct.

--Rik

Photosbykev
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Post by Photosbykev »

rjlittlefield wrote:That all looks correct.

--Rik
Thank you Rik, that microscope slide you suggested is a very useful little tool.

regards
Kev

ChrisR
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Post by ChrisR »

Yes, the LSA isn't precisely 200mm. I measured one a year or so ago.
Then forgot..
Chris R

Photosbykev
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Post by Photosbykev »

ChrisR wrote:Yes, the LSA isn't precisely 200mm. I measured one a year or so ago.
Then forgot..
rightly or wrongly, I mounted the LSA on a M42 tube extension and a M42 > M52 helical focuser and then used the focuser to focus on a star last night so it's at a true infinity.

regards
Kev

rjlittlefield
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Post by rjlittlefield »

Photosbykev wrote:I mounted the LSA on a M42 tube extension and a M42 > M52 helical focuser and then used the focuser to focus on a star last night so it's at a true infinity.
That's the correct approach to nominally minimize aberrations.

If having exactly 10.0X magnification ever becomes important, you can slightly increase the extension behind the LSA to achieve that. With the roughly 3% increase needed to go from 9.67X to 10.0X, you would never notice a change in aberrations. This is the method that I used to match magnification and field size in my tube lens tests at http://www.photomacrography.net/forum/v ... hp?t=23898 .

--Rik

Photosbykev
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Post by Photosbykev »

rjlittlefield wrote:
Photosbykev wrote:I mounted the LSA on a M42 tube extension and a M42 > M52 helical focuser and then used the focuser to focus on a star last night so it's at a true infinity.
That's the correct approach to nominally minimize aberrations.

If having exactly 10.0X magnification ever becomes important, you can slightly increase the extension behind the LSA to achieve that. With the roughly 3% increase needed to go from 9.67X to 10.0X, you would never notice a change in aberrations. This is the method that I used to match magnification and field size in my tube lens tests at http://www.photomacrography.net/forum/v ... hp?t=23898 .

--Rik
I'm not overly worried by the exact magnification, 9.67x is just fine now I know what it is :) I need to flock line the extension tube to minimise any internal reflections and I'm good to go :)

regards
Kev

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