[APML] FM3A MLU and a manual stacking question

["Eric Z. Beard" <ericzbeard@yahoo.com>]

Hi everyone,

I sure am glad to see SEDS back up and running.. anyone know where they got the
funds for the new server?  Many thanks to whomever the kind benefactor was.

I have two questions today:

First of all, I'm considering selling my OM-1 setup in favor of an FM3A.  But
I'm not sure about the mirror lock-up on the FM3A when in Bulb mode.  How does
this work?  From what I have read, the MLU is tied to the timer.  I'm used to
just flipping the mirror down on my OM-1 and leaving it there.

The second question is about manual stacking of images in Photoshop (or the
equivalent).  Let's say I have 3 nice images that I want to align and stack,
and I plan to use the average blending mode by setting the opacity of each
overlaid image to 50%.

I start with the first image, which sits on the bottom with 100% opacity, then
I overlay the second at 50%, and when I'm happy with the alignment, I flatten
the image.  Then I repeat with the 3rd image.

Here's the problem: Let's pick an arbitrary pixel in each image, and to narrow
it down, let's say the RED value is 100 in the first, 100 in the second, and 70
in the third.  A real average would be 100+100+70=270/3=90.  But with the
aboove method, after the first flattening, the red value sits at 100.  Then
after averaging with the third, it is 100+70=170/2=85.  85 is not the real
average.

Does that make sense?  Any ideas on how to solve it?

Thanks!

EZB

=====
Eric Z. Beard
http://www.honeydewphoto.com/eric
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