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Re: [OM] Lens testing, including centering

Subject: Re: [OM] Lens testing, including centering
From: Mike Gordon via olympus <olympus@xxxxxxxxxxxxxxxxx>
Date: Mon, 21 Feb 2022 00:13:44 +0000 (UTC)
Cc: usher99@xxxxxxx
<<If I were looking for an ideal copy of a Blogogon 8/1.0, all it takes is a 
couple of minutes and a few shots, to document each one, as I rent or buy and 
return. No adjustment/accommodation <<for different foliage, light, etc. as 
with this outside technique.

The Blogogon gets nice reviews.  Filed curvature can vary with focusing 
distance.  Not sure how far away the test targets must be for an ultrawide and 
is that practical?  Otherwise I would agree I like your methodology and it has 
advantages.   I had had to quickly determine centering issues so proceeded 
accordingly.   

<<Is this from Roger? I'm wondering how someone outside of Oly production 
<<engineers can know this, especially statistics.

That data was from an Oly engineer during one of those long boring interviews.  
I slogged through the whole thing.


<<<<Roger has also stated MFT lenses have more sample variability than others.

<<Might this be related to scale? Missing spec by 0.01 mm makes a larger 
<<difference for 4/3 than FF?

Good question.  Your speculation seems reasonable to me. 

<<<OK, this raises a question. Why does linear distortion matter - for this 
specific purpose? If the stars are nice pinpoints, does it matter if their 
locations differ a bit from a true star map?

Agreed, but any tutorial I have read said to not correct distortion.  Also 
might screw up the stacking with dark frames.  Do you think the stars would not 
be affected? You know more about how the various correction algorithms work 
than almost anyone. 

Unstandardized, Mike
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