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02-07-2022, 11:59 AM   #1
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Bellows To Digitize Negatives

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Mornin' folks!

I'm hoping to start using my M42 bellows with slide copier to digitize my 35mm film negatives.

I'm using my K-70 with an M42 adapter, connected to the bellows and slide copier.
My problem is with the lenses I currently have, the magnification is too great - that is, I can't back up enough to get the whole negative in the frame. The resulting digitizing is substantially cropped.

Therefore, I need a lens that produces a lower magnification.
One that allows me to use my APS-C camera to capture a full frame 35mm film negative.

My problems come around when considering the crop-factor... I've never really good at considering 'equivalencies'

I'm guessing a Super-Takumar 55mm f/1.8 may suit my needs (spec sheet attached).
With the 1.5x crop factor, I'd need to have an equivalent coverage of 36mm x 54mm, no?
Since this lens has a lowest magnification is 0.66, that would equal 37mm x 55mm area.
Meaning I'd have more than enough room to capture the full negative..

May someone please double-check my reasoning?

Thanks in advance!

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02-07-2022, 12:16 PM   #2
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Getting the slide copier to work with APS is difficult without providing some sort of extension to the bellows between the lens and the slide/negative. Alternatively, a lower magnification lens may help solve the problem (e.g. 35mm).

In regards to theory, I have found the tutorials on the site below to be very helpful.

Coin Imaging | Optics Articles

The third article is the one that is applicable to this case, but the #1 and #2 are helpful to understanding of #3.


Steve
02-07-2022, 12:23 PM   #3
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This is one of those situations where I'd suggest :- "If I wanted to go there I wouldn't start from here!"
Seriously, the bellows are simply not the tool for the job with a 55mm lens ... you need either a wider angle lens or a set of extension tubes.
A 36mm tube seems to be about right with my Pentax-M 50mm f/2.
Alternatively, a macro lens ... my Tamron Adaptall-2 90mm seems to do the job "as close as dammit" by itself or spot-on with a 12mm extension tube.
Hope this helps
02-07-2022, 12:56 PM   #4
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QuoteOriginally posted by kypfer Quote
This is one of those situations where I'd suggest :- "If I wanted to go there I wouldn't start from here!"
That is sort of my perspective, except that I would suggest a bellows, but not the slide copier setup.

I use the Bellows Unit K for fine work where 0.67x magnification (FF equivalent) is essential.

PENTAX Bellows Unit K reviews - Pentax Camera Accessory Review Database


Steve

02-07-2022, 01:45 PM   #5
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The formula for a simple lens and magnification might help in your case: 1/FL = 1/IMG + 1/OBJ and MAG = IMG/OBJ where FL is the lens focal length, IMG is the lens-to-image distance and OBJ is the lens-to-object distance. These might allow you to approximate what lens focal length you need given the bellows extension range and your known magnification (0.67). Start with the distance span that your bellows allows for lens-to-image distance, and the distance you want to place your negative (the lens-to-object distance) from the lens. You know you want a final MAG of about 0.67 but that can be adjusted once you get an acceptable focus somewhere in the middle of your bellows range.

Last edited by Bob 256; 02-07-2022 at 01:50 PM.
02-07-2022, 01:46 PM   #6
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It might just work. I don't have the 55mm Takumar but my 18-55mm on my Auto Bellows A seemed to work. Some of the slide mount was visible but that's what you expected. I didn't unbox the slide copier but hand holding the slide there appeared to be enough room for it to work.

If it works in practice I wonder why someone hasn't come up with this earlier? The 55mm may not be the sharpest lens in the bag but is probably good enough.
02-07-2022, 02:53 PM   #7
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I am using a Makinon Zoom slide copier, but that also works only with Full Frame camera.

There is one at ebay UK at this moment for 20 pound

Makinon Zoom Slide Duplicator - For SLR 35mm Film Cameras* + Case BOXED | eBay

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Last edited by Sakura; 02-07-2022 at 03:01 PM.
02-07-2022, 03:01 PM   #8
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I recently came across this informative video on YouTube which you might find helpful. He's using a K3 and Pentax bellows. He explains the process quite well, I thought.


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02-07-2022, 04:20 PM   #9
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There are a number of DIY posts on PF on using the Pentax Bellows and slide copier and APS-C bodies. There was just a thread in the last six or so months as I recall.
02-07-2022, 05:10 PM   #10
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I didn't have much luck with the bellows and instead used a light table, film holder, and macro lens. I only experimented a little, there are other people that have done far more, but the results were promising.
02-07-2022, 05:14 PM   #11
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QuoteOriginally posted by stevebrot Quote
Getting the slide copier to work with APS is difficult without providing some sort of extension to the bellows between the lens and the slide/negative. Alternatively, a lower magnification lens may help solve the problem (e.g. 35mm).

In regards to theory, I have found the tutorials on the site below to be very helpful.

Coin Imaging | Optics Articles

The third article is the one that is applicable to this case, but the #1 and #2 are helpful to understanding of #3.


Steve
Great tutorials thanks !
02-08-2022, 02:09 AM   #12
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QuoteOriginally posted by Not a Number Quote
It might just work. I don't have the 55mm Takumar but my 18-55mm on my Auto Bellows A seemed to work. Some of the slide mount was visible but that's what you expected. I didn't unbox the slide copier but hand holding the slide there appeared to be enough room for it to work.
If it works in practice I wonder why someone hasn't come up with this earlier? The 55mm may not be the sharpest lens in the bag but is probably good enough.

"I wonder why someone hasn't come up with this earlier?"
Probably because the 18-55mm doesn't have an aperture ring … one normally closes down a couple of stops to maximise the performance and compensate for any slight focussing errors
02-08-2022, 05:39 AM   #13
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The Pentax slide copiers work with lenses that has a 49mm or 52mm filter size. The 18-55mm does not fit the bill. It also has a narrow range of extension that was designed for 135 (full frame) negs, 50mm lens and 135 image size. There is a little scope to crop/enlarge/adjust the image but not much. Something like the 18-55mm is just too big to fit.

As far as the focal length goes, 50mm will probably not play nice with APS-C. A 35mm or 28mm is more ideal, but some experimenting may be required. On full frame, a 50mm macro is said to work better because it has a flatter focus plane. Unfortunately, there is no modern macro shorter than 50mm that has an aperture ring.
02-08-2022, 10:35 AM   #14
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QuoteOriginally posted by kypfer Quote
"I wonder why someone hasn't come up with this earlier?"
Probably because the 18-55mm doesn't have an aperture ring … one normally closes down a couple of stops to maximise the performance and compensate for any slight focussing errors
I meant with a 55mm Takumar M42 prime lens since that is the lens in discussion. The 18-55 was used only as proof of concept.
02-08-2022, 06:39 PM   #15
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FozzFoster. You need to find one of these lenses that zoom and have a macro setting. I just used mine to “scan” sides using a Pentax bellows. Allowed me to get the proper framing of the slide using a k-3. Worked great

SMC Pentax-M 40-80mm F2.8-4 Reviews - M Zoom Lenses - Pentax Lens Reviews & Lens Database

Tom
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