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M42 aperture adapter w 90mm schneider barrel lens
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PostPosted: Wed Mar 11, 2020 7:07 pm    Post subject: M42 aperture adapter w 90mm schneider barrel lens Reply with quote
I got this Chinese m42 aperture adapter to give additional flexibility with some of my lenses eg projector, process or barrel lenses. It has no clicks. So just best guess as to next appropriate aperture. These were taken with 90mm apo-componon hm F4. From wide open to completely stopped down, using shutter priority on a tripod, A little bit windy so might show some motion blur towards the end of the series. Anybody know how to derive the f numbers? Sorry they are a bit overexposed.













PostPosted: Wed Mar 11, 2020 10:46 pm    Post subject: Re: M42 aperture adapter w 90mm schneider barrel lens Reply with quote
jamaeolus wrote:
I got this Chinese m42 aperture adapter to give additional flexibility with some of my lenses eg projector, process or barrel lenses. It has no clicks. So just best guess as to next appropriate aperture. These were taken with 90mm apo-componon hm F4. From wide open to completely stopped down, using shutter priority on a tripod, A little bit windy so might show some motion blur towards the end of the series. Anybody know how to derive the f numbers?


Probably easiest using Av rather than Tv. Just check your ttl meter for the shutter speed as you stop down. For example, choose an ISO that'll give you a well-exposed shot at 1/1000 sec wide open, then watch the shutter speed as you close down. 1/500 sec will be f/5.6, 1/250 will be f/8 etc etc Wink


PostPosted: Thu Mar 12, 2020 1:38 pm    Post subject: Reply with quote
Great rendering, by the way! Very natural and bright.


PostPosted: Thu Mar 12, 2020 6:15 pm    Post subject: Reply with quote
hmm I didn't actually look at these after I posted. The ARW files on my galaxy tab s9 looked way better (sharper ) at ever aperture. I will redo the test when I get a chance. I will also take kypfer's advice on settings. I also really must dig through my bins as I have a couple relatively soft WO projection lenses (A Kodak ektar and a Staeble Stellar) that I really want to try.


PostPosted: Thu Mar 12, 2020 10:22 pm    Post subject: Reply with quote
jamaeolus wrote:
hmm I didn't actually look at these after I posted. The ARW files on my galaxy tab s9 looked way better (sharper ) at ever aperture. I will redo the test when I get a chance. I will also take kypfer's advice on settings. I also really must dig through my bins as I have a couple relatively soft WO projection lenses (A Kodak ektar and a Staeble Stellar) that I really want to try.


It isn't your lens or computer. MFLenses seems to use a compression algorithm when loading images above a certain size. If you click on your image it will open in a big version on a separate page, which is usually noticeably sharper.
Tom


PostPosted: Thu Mar 12, 2020 11:48 pm    Post subject: Reply with quote
The highlights look blown??


PostPosted: Sat Mar 14, 2020 4:37 pm    Post subject: Reply with quote
Blown highlights, motion blur, photos display poor technique. That's what I get for using a part of the camera I rarely ever use. I nearly always use manual exposure and visually correct using the lowest ISO to what looks good to my eyes. I wanted the exposure to be controlled to show just the sharpness and depth of field of the adapter. Embarrassing learning experience.


PostPosted: Sun Mar 15, 2020 5:54 pm    Post subject: Reply with quote
A second attempt.
Wide open:


About half closed (guessing fCool


The exposure control was accomplished by adjusting the shutter speed looking at the monitor. So not a perfect match but displays what I was trying to show.


PostPosted: Mon Mar 16, 2020 2:46 am    Post subject: Reply with quote
I really like those last two photos!

You can calculate your f number using this formula: f-stop = focal length / aperture circle diameter .

All the best,

Paul
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