Olympus-OM
[Top] [All Lists]

Re: [OM] Lens Comparison Test Procedure

Subject: Re: [OM] Lens Comparison Test Procedure
From: PCA Cala <PCACala@xxxxxxx>
Date: Fri, 3 Apr 1998 05:23:43 EST
Hi BW:

Sounds like a fruitful exercise, if you can stick as close to possible to your
real world situations.

> Should I use flash, the lamps or take it outside?
2 lamps at 45 degree angles to minimize hot spots

>  What slide film should I use?
Velvia which has superior sharpness to Kodachrome 25

>  Is Sensia 100 OK or should I go to 25 ASA?
See above.  In BW, I'd choose Technical Pan to minimize loss of image quality
attributable to film

>  What subject should I use for flat?
The most detailed you can find.  Perhaps a colorful foreign currency bill.  My
favorite "real world" subject is a highly detailed topographic map, but at 1:2
testing it isn't detailed enough.  For 1:20, it is.  A fine quality halftone
reproduction might work, so would a contact print of an aerial photograph, but
both are better suited to 1:10

>  What subject should I use for 3-D?
I wouldn't since I find it meaningless.  Depth of field tables or the lines on
the lens barrel will predict the results you get.

>  Should the subject be Black & White or Color?
No opinion, BUT: Consider what you will use the lens at.  Perhaps 1:2 is too
restrictive.  Each lens will have it's own best use!

>  What do the professional labs use?
They are likely too busy to test, although I don't know what you mean by lab.
Read the photography magazine test procedures for theirs.  Air Force high
resolution test chats have been a favorite since they became available in the
early 1950's.  There are Internet sources for EPS files of these.

>  Evaluation can be done with a Peak 4X loupe and light table or should I
borrow a 8X or 10X?
My favorite in the past has been a microscope with bottom illumination!  A
poor second, due to marginal optical quality, is a folding pocket microscope,
like a 30x Panasonic.  A loupe won't magnify enough.  A slide generally has
the limitation of a poor projection lens, although it is a real world
evaluation for folks who take and project slides.
Recollection:  As a teen ager, I fitted a 100 mm f/3.5 (F/4 ?) Canon Serenar
lens (Canon series IV and V rangefinder vintage) in a barrel and used it as a
projection lens.  For real critical detail I stopped the lens down. When I
went off to college I put the original elements back in the barrel.  I got an
angry phone call, at some point, that the image from the projector was
unfocusable.  . . . I had put the elements back in the wrong way!  I still
don't know how that happened.  I knew the Tessar formula well enough that I
rectified the error in a minute when I got back home.

>  I could scan them into Photoshop?
Too much detail loss here due to scanner dpi limits

>  Should I mount the slides or leave them uncut?
Either way.  Mounted are easier to label and lend themselves to slide
projector evaluation.  Unmounted saves cost and time and the frame numbers
correspond to your procedure notes, albeit with frame sequence errors due to
the occasional goof along the way.

>  What should I look for in the slides?
Detail, detail, detail and how much contrast there is between the dark details
and white backgrounds.  When one or both aren't there, try and infer why not.
Perhaps too wide an aperture to compensate for aberrations, too much curvature
of field, or ???

Final comments.  I'd use a Varimagnifinder to ensure focusing accuracy and
tape the focusing ring down when shooting through a range of apertures.

Gary Reese
Las Vegas, NV

< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >


<Prev in Thread] Current Thread [Next in Thread>
Sponsored by Tako
Impressum | Datenschutz