[visiono]

I got my hands on a 28m smc pentax f2.0 lens (the rare one) and along with a canon 50d dslr I want to copy or photograph a 645 medium format film negative. Those who are unaware this is like scanning a film negative only cheaper , faster and sometimes better than expensive scanners.
I will use the 28mm smc with a reverse ring so i can use it as macro. My question is , will this work? How close will i have to be to the negative with a reverse ring on a 28mm and apsc sensor? Will I get good results at f5.6?

People recommend a 105mm on a full frame dslr to do this type of work but I don't have a high quality macro lens in this focal length . I have a Sigma 17-50 f2.8 with a 78mm filter diameter. I suppose I could reverse thing that but the quality is very inferior to the smc 28mm.

thanks

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Last edited by visiono; 12-24-2016 at 09:43 PM.

[alamo5000]

I have done some macro shooting with 50mm and 28mm lenses (reversed). Although I am not a big time macro guy I am familiar with it.

I can say that I have never heard of the process you're undertaking either. That said with a 28mm lens reversed I think you will get really good detail and of course you're going to have to get really close. The good thing is your target isn't moving. I was trying to take pictures of bugs and such but with a flat surface I think you could get it done.

From what little I know you might want to stop down to like f8 and work on getting better lighting. Your other challenge will be holding the camera flat and on the same plane as your negative. I would also think you will end up having to stitch the image together. A 28mm lens reversed is going to give a whole lot of magnification.

[photoptimist]

A 645 negative is 56 x 41.5 mm and the APS-C frame of the Canon is 23.7 x 15.6 mm so you need a magnification of under 1:2.66 to get the whole negative in one shot.

Unfortunately, a reversed 28mm is almost certainly going to be very high magnification (greater than 1:1) so unless you want to do each negative as a set of tiles and merge them panorama-style, this won't work.

You could try reversing the Sigma -- don't buy the reverse ring yet, just hold the lens reversed, look through the viewfinder, and then point the rig at a ruler to see if it can work and whether you can see at least 42 mm across the height of the frame.

[visiono]

thanks everyone. I also have 2 mamiya 645 lenses. 80mm f2.8 and 150mm f3.5. Could I reverse ring and use any of these on my canon 50d? which would be better? 150mm ?

[photoptimist]

thanks everyone. I also have 2 mamiya 645 lenses. 80mm f2.8 and 150mm f3.5. Could I reverse ring and use any of these on my canon 50d? which would be better? 150mm ?

Maybe. It's worth just trying it with hand-held rig just to see if it can focus at a sufficient distance to see the whole negative. Of course, you may find you'll need a bellows to get the right camera-to-lens distance especially with the 150.


Good luck!

[Canada_Rockies]

28 mm reversed on a 52-49 step down ring gives 2.1x magnification. For 1 to 1, a 50 mm would be a better choice.

[leekil]

I got my hands on a 28m smc pentax f2.0 lens (the rare one) and along with a canon 50d dslr I want to copy or photograph a 645 medium format film negative.

I'm not sure if the image quality of that lens would be as good reversed as it is normally. Anyone have any experience with that type of usage?

[wombat2go]

I made a little geo-optics diagram for the 645 negs on to apsc.
https://app.box.com/s/blhtruiyx6si1lwumbfy4ncgjnubs7eh
It looks like you need a lens in the range of 90mm, along with a pentax bellows, or at least a helical extension tube.
It is not likely a 28mm lens will work because its N2 needs to be 38mm from the sensor, whereas the pentax registyer is 45.6mm

[Kerrowdown]

I got my hands on a 28m smc pentax f2.0 lens

It'll be absolute rubbish for what your trying to do, you must give it to me immediately.

[alamo5000]

thanks everyone. I also have 2 mamiya 645 lenses. 80mm f2.8 and 150mm f3.5. Could I reverse ring and use any of these on my canon 50d? which would be better? 150mm ?

When reversing lenses the longer the lens the LESS magnification you get. Conversely the shorter the focal length the more magnification you get.

If it were me I would give the 28mm or even an old 35mm lens a go. You will end up stitching the photo digitally but you definitely will get a lot of detail.

The biggest problem you will find no matter how you do it is the lighting. Getting enough light without glare is what you should be concerned with IMO.

[visiono]

I tried all 3 lenses just hand holding. The 80mm mamiya was the only one that could focus but get this, only at 1 inch from the lens mount.
photoptimist, when you say using the 28mm ff lens will give me tiles , how many do you mean? like 10 ? I don't mind stiching 10 together, i will also get a very high mp file. So a 50mm ff pentax would be a better recomendation?

[photoptimist]

If what Canada_Rockies said is true for the 28 mm f/2 lens, then the tiles would be tiny and you'd need at least 30 to scan one negative.

A 50 mm lens would probably work better but it's really tricky because it's very sensitive to the choice of lens and the length of your reversing mount.

If I hand-hold a reversed lens on a Pentax APS-C camera (a K-10D in this case), the largest FOV varies hugely across different 50 mm lenses:

Pentax K 50 mm f/1.2: 16 x 24 mm
Olympus Zuiko 50 mm f/1.4: 17 x 26 mm
Olympus Zuiko 50 mm f/1.8: 26 x 39 mm
Takumar M42 55 mm f/1.8: 41 x 62 mm

The longer the length of the reversing mount, the smaller the tile size.

[visiono]

Dcshooter, did you say 50mm with extension tubes? you don't think it would work with the 28mm and 3 tubes stacked? Manual macro lenses are fairly cheap. The tube method is not as sharp as a real macro prime yes?

[visiono]

do you mean have the camera and lens hood rest on the light table yet not on the neg assembly? I don't understand the idea of the larger lens hood. Thanks, so it sounds like a dedicated macro is required for pro results. which do you feel is better? Vivitar 100mm f3.5 Macro, pentax m 50mm f/4 macro or Sigma 50mm F2.8 AF Macro?

[wombat2go]

Has anybody done a mf neg scan using stitching?
Is the distortion due to stitching artifacts evident?