Puzzling glow in inverted SMC-M 28mm/3.5

**K-Three** · 11-20-2016, 04:55 PM - **1 Like**

Interesting,
Got my curiosity up, and made me dig out my reversing ring and M 28, 3.5; put it on my K5, and played around with a single LED flood off the side. My reversing ring is 49mm so no other adaptors in the system.
Exposure was f/8 @1s, iso 160. I used a #3 extension tube from the Pentax Auto K set as a lens hood for some, never noticed a big difference one way or the other.
The subject is a large commemorative bronze coin.
This combination does get you very close.
I played with a number of different subjects, some more reflective others not so much. This coin is the most like what you showed for a subject.
On more reflective subjects I was seeing a lot of the lens and the chrome of the lens mount in the subject. I would think about masking that off with something to knock back reflections if I was doing something critical.
Never saw anything like the flare you are getting. Don't know what to think about that now.

I would take any extra glass out of that system, I don't think filters are going to help, only degrade the image more, more surfaces to reflect off of.

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LensBeginner · 11-21-2016, 11:18 AM

Well, it's fiddly for sure...

First I tried shooting something other than coins, and the page of a newspaper proved less problematic - but the glow was still there albeit much less evident.

Second I tried fabricating a paper cutout (I'll do it with proper cardboard as soon as I have the chance & time), with a hole about 1cm in diameter, and fitted it between the lens' front element and the step-up ring.
This solved the issue, and if it's still there it's much more difficult to notice.
I still have to try the coin again though, but I'm pretty satisfied. DoF is obviously razor-thin, and I don't have the equipment to focus accurately (rails etc.), but at least the result is decent.

Thanks all for your invaluable feedback :-)

ok by Lens Beginner, su Flickr

**K-Three** · 11-21-2016, 08:49 PM

Yes, that was the key piece of gear I had to find was my macro focusing rail.
No way I was going to get and keep sharp focus without it that close.
I used to do a lot of macro, but not as much these days, still have most of my gear from film era,
Extension tubes, reversing ring, 100 M macro, and that rail, all official Pentax from the late '70s early '80s

Lots easier these days with instant feed back on how you are doing for focus and exposure.

Keep at it, you'll get there.

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11-21-2016, 11:18 AM	#17
LensBeginner Veteran Member Join Date: Sep 2014 Photos: Albums Posts: 4,696 Original Poster	Well, it's fiddly for sure... First I tried shooting something other than coins, and the page of a newspaper proved less problematic - but the glow was still there albeit much less evident. Second I tried fabricating a paper cutout (I'll do it with proper cardboard as soon as I have the chance & time), with a hole about 1cm in diameter, and fitted it between the lens' front element and the step-up ring. This solved the issue, and if it's still there it's much more difficult to notice. I still have to try the coin again though, but I'm pretty satisfied. DoF is obviously razor-thin, and I don't have the equipment to focus accurately (rails etc.), but at least the result is decent. Thanks all for your invaluable feedback :-) ok by Lens Beginner, su Flickr

11-21-2016, 08:49 PM	#18
K-Three Loyal Site Supporter Join Date: May 2014 Location: Pugetopolis, WA Photos: Gallery Posts: 938	Yes, that was the key piece of gear I had to find was my macro focusing rail. No way I was going to get and keep sharp focus without it that close. I used to do a lot of macro, but not as much these days, still have most of my gear from film era, Extension tubes, reversing ring, 100 M macro, and that rail, all official Pentax from the late '70s early '80s Lots easier these days with instant feed back on how you are doing for focus and exposure. Keep at it, you'll get there.