Re: [OM] The KEH upgrade

Subject: Re: [OM] The KEH upgrade
From: Moose <olymoose@xxxxxxxxx>
Date: Tue, 12 May 2020 22:06:23 -0700
On 5/12/2020 4:49 PM, Ken Norton wrote:
AHA! Compare vignetting.
Holding My Breath Moose
No need to worry. The vignetting I'm seeing is specifically related to
the protruding lens mount into the corners. It's something I see
referenced all over the Interwebs regarding the SONY Alpha series. I
expected to see it and when I go looking for it, I can find it.

Not buying it.The throat of an Oly 25 mm extension tube is 37 mm, at the end away from the lens. That of the Fotasy adapter is 41.4 mm, at a distance eq. to a 28 mm tube. Larger opening, further away.

The Oly 14 mm tube is also 37 mm. The 7 mm tube's throat is 43 mm, perhaps for 
the cone of light reason I mentioned.?

I don't doubt that people are seeing vignetting, but there are multiple 
possible other causes for that.

other brands have a larger throat. Also, I've noticed a little corner
darkening related to sensor offset, but this is with the native lens
too. Regardless, it's not a big enough of an issue for me to worry
about at all. I almost always do a little cropping of my images
(usually because I have to level the image)

Separated at birth, still!

and if I think in terms of
35mm film, I was rarely able to use 100% of the image area either.

Yeah, never used to be bothered, until I got a scanner and digital cameras. :-)

The other optical vignetting with the OMZ lenses is certainly
prevalent with some of the lenses, but is either easily addressed in
the computer or eliminated by stopping down a couple of stops. The
wide-angle lenses certainly have a lot of vignetting wide-open,

As was true on film.

  but it gives the images character too. :)

Sometimes I leaves it, sometimes I don't. Not really referring to OM lenses, though, but to my motley army of other old and odd lenses.

As to the 300/4.5, I've found that this lens underperforms on the
crop-sensor cameras from what I can only surmise is an overly
"telecentric" lens, such as a super-telephoto where the exit glass is
so far from the film-plane, has the image compromised by the sensor's
microlenses that are designed for less telecentricity.

Whatever the reason, it is unimpressive on a 4/3 sensor.
The 300/4.5 could give me exceptionally sharp images on the 6D and I
can see that it's doing the same on the SONY.

Perhaps I'll find an extra round TUIT.

Dark Edges Moose

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