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11-25-2015, 09:15 AM   #1
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Suggestions for improving the quality of photographed negatives

Recently I started trying to scan a bunch of my fathers films going back to early seventies. In the process I went through taking photos with


* Tamron 70-200 at minimum focusing distance
* Pentax M50/1.7 at minimimum focusing distance (sharper)
* Pentax M50/1.7 with 23mm extension tube (bigger)
* Pentax M50/1.7 with 31mm extension tube (bigger)


All of the above against white of my monitor with amped up brightness and with film held between two cardboard pieces pressed together.


After the initial joy that I can get usable results I finally noticed that though central sharpness is excellent, the falloff is so fast I'd need to stich around six photos to cover one 35mm negative with satisfactory sharpness.




Then I changed the setup to camera pointing down from a tripod to film held between my phone serving as a light table and a chunk of safety glass. Instead of film I used a piece of paper with a fine print on it so I can easier trace the boundaries of 'sharp enough'. Even with this setup, I couldn't achieve satisfactory sharpness across the frame. Switching to FA43, it was a bit better but not significantly.


All of the above was done at f8 and occasionally f11 and above but without noticeable difference.


My questions here are:


1) Can I do better with the lenses I have? I reckon DoF is around 1mm at 50mm with 0.65 ratio so it seems normal to me I'm losing sharpness towards edges fast.
2) Would a macro lens be significantly better?
3) Finally, what focal length macro lens would best server this purpose; wide or long? I'm specifically considering 35mm, 50mm and 100mm Pentax offerings.


Thanks,

11-25-2015, 09:24 AM   #2
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QuoteOriginally posted by cxdoo Quote
1) Can I do better with the lenses I have? I reckon DoF is around 1mm at 50mm with 0.65 ratio so it seems normal to me I'm losing sharpness towards edges fast.
Not sure - the telepathy isn't one of my talents :P - but being serious it it reather impossible to judge the results you are getting without actually *seeing* them . From your description it seems that film isn't flatten and also lenses' field curvature could be a factor. Hard to say though without seeing your photos

QuoteOriginally posted by cxdoo Quote
2) Would a macro lens be significantly better?
Most probably yes. You could still do bad with macro lens , but provided your technique would be good and the focusing precise , a real macro lens will give you best results possible, especially flat field of macro with no curvature will reduce sharpness falloff which you can see with your other lenses.

QuoteOriginally posted by cxdoo Quote
3) Finally, what focal length macro lens would best server this purpose; wide or long? I'm specifically considering 35mm, 50mm and 100mm Pentax offerings.
I think 50 or 100mm will be best, 35mmis definitely too wide and the working distance would be very small.
11-25-2015, 11:26 AM   #3
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DFA-50/2.8 macro or DFA-100/2.8 macro or there earlier versions should do the trick. They seem to have very good flat field of view focus and edge to edge sharpness. With good lighting, slide scanning using both these worked a treat.
11-25-2015, 01:33 PM   #4
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QuoteOriginally posted by manntax Quote
but being serious it it reather impossible to judge the results you are getting without actually *seeing* them .
Thanks all for suggestions, I will put up relevant examples as soon as I can.

11-25-2015, 05:05 PM - 1 Like   #5
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QuoteOriginally posted by cxdoo Quote
I went through taking photos [...] against white of my monitor with amped up brightness and with film held between two cardboard pieces pressed together.
I used an identical setup here, but with a macro lens. I've uploaded the full-res image here if you'd like an example of what's possible with a flat-field lens. Note that film-lens alignment was likely imperfect.
11-26-2015, 01:46 AM   #6
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QuoteOriginally posted by Jens Lyn IV Quote
I used an identical setup here, but with a macro lens. I've uploaded the full-res image here if you'd like an example of what's possible with a flat-field lens. Note that film-lens alignment was likely imperfect.


Thank you. From what I see you also have slight defocus on the left side, however the area where dust specks are in focus is larger than in my photos.
Well if macro lens brings me from stitching 6 photos to stitching 2, it'd be worth it.




QuoteOriginally posted by Professor Batty Quote
Here is an example from a 6x6 neg (TXP) with my set up:

This looks great. I also have some rolls of 6x6 to scan hopefully they will turn out good.
11-29-2015, 08:46 AM - 1 Like   #7
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The biggest problem you will have with a freehand system is getting the film parallel with the sensor and I would suggest you look at some sort of slide copying device to attach to the end of your lens to alleviate this problem.

I found it interesting that you tried a Pentax 50mm 1.7 so I decided to do a few tests of my own with a Pentax M 50mm f1.7 on a 31mm extension tube against a Macro Takumar 50mm f4, the results were quite surprising.

There are slight differences in the magnification of the samples below because of the physical difficulties of setting the lenses both the same, but it's not enough to matter. Both lenses were set at f8.

First the Macro Tak, full frame




Then the Pentax M full frame




Macro Tak 100% centre crop




Pentax M 100% centre crop




Macro Tak 100% left crop




Pentax M 100% left crop




I didn't bother to post crops from the right because with both lenses they showed the same consistency as the left.

My opinion:

Although the Macro Takumar shows a slight overall lead, the Pentax M 50 f1.7 is more than capable of being used to copy negatives.
The M does show a slight fall off towards the edges but this is only just noticeable when viewed at 100% and for most purposes this wouldn't show.

Hope that helps

Ramon

11-29-2015, 12:10 PM   #8
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Hey thanks a lot!
I had a hunch M50/1.7 should be fine on extension tubes and at f8 and that main reason my results are unsatisfactory is my poor technique. Now I have something to strive for.

:waits for everyone in the house to go to sleep:
11-29-2015, 04:07 PM   #9
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If you are looking at a significant number of images to copy/digitize,
I would consider looking at a flat bed scanner with film copying capability,
I have an Epson 4180 that has a back-light in the lid, can do film up to 2-1/4 roll film sizes,
It was only a few hundred$, not sure what the current model is, or what may be out there used.
Something like this should be more than adequate for family type, snapshot photos you want to be able to share with extended family

Another option would be to send them out to a commercial lab to be scanned,
Without a dedicated copy stand set up to keep your camera square to the copy, I forcast a lot of frustration in your future.
11-29-2015, 08:27 PM - 1 Like   #10
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QuoteOriginally posted by K-Three Quote
Without a dedicated copy stand set up to keep your camera square to the copy, I forcast a lot of frustration in your future.
I agree,
With a 50 mm lens at f/8, the depth of field at 123 mm is about 0.7 mm (+/- 350 micrometre) -for a COC roughly based on 1400 pixels in the height of the aps-c sensor.

Th old Pentax Slide Copier M, and the Pentax Bellows M were built accurately of machined parts , but on the ones here, the weakness is in the slide coupling on the slide copier.
That coupling causes a "slop" of about +/- 55 micrometre at one edge of the 35mm frame.
Below is a phot of the old Pentax copier being measured with the vintage measuring gear I have here.
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11-29-2015, 08:56 PM   #11
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I scan negatives using my k3, a home built light box, a jig to hold things straight(ish, I'm working on it), a slide holder and a 100mm macro lens. I'd highly suggest getting a macro lens if you're serious about it, I can't come close to the same quality with extension tubes. (Edit I should say I'm sure it's definitely possible, but my experiments with extension tubes have never come close to matching macro shots done with my macro lens.)

If you can wood work, you can make something for really cheap that gives good results. Here's a good example of what's possible, check out the high res version.

11-30-2015, 01:09 AM   #12
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QuoteOriginally posted by K-Three Quote
If you are looking at a significant number of images to copy/digitize, I would consider looking at a flat bed scanner with film copying capability,

I tried that already and wasn't really satisfied. It works but I believe it can be done much better.


QuoteOriginally posted by K-Three Quote
Something like this should be more than adequate for family type, snapshot photos you want to be able to share with extended family


No doubt about that. However this is more of a hobby project without any timeframes or obligations to family members so I'm exploring all the options.

QuoteOriginally posted by K-Three Quote
Another option would be to send them out to a commercial lab to be scanned,


I considered this too and still might send a film or two to see what kind of results I can expect.

QuoteOriginally posted by K-Three Quote
Without a dedicated copy stand set up to keep your camera square to the copy, I forcast a lot of frustration in your future.


It's slowly dawning on me what I need, in equipment, skill and time.




QuoteOriginally posted by wombat2go Quote
Below is a phot of the old Pentax copier being measured with the vintage measuring gear I have here.


Thanks, this is very informative. I'm considering something like this Products
I'd put film on the bench between light table and a thick piece of safety glass to keep it flat. Then I reckon the most difficult part would be to align sensor and film planes but hopefully I'd need to do that only once per session.

---------- Post added 30th Nov 2015 at 10:16 ----------

QuoteOriginally posted by bobbotron Quote
I scan negatives using my k3, a home built light box, a jig to hold things straight(ish, I'm working on it), a slide holder and a 100mm macro lens. I'd highly suggest getting a macro lens if you're serious about it, I can't come close to the same quality with extension tubes. (Edit I should say I'm sure it's definitely possible, but my experiments with extension tubes have never come close to matching macro shots done with my macro lens.)

-ish is the keyword for where I'm at now.
I had another round of frustration last night but between using mobile on top of a stack of books as light table and a tripod as copy stand there were too many parameters that could have gone wrong. However I'm in a no hurry so I'll take my time until I sort it out (or realize I'm incapable of doing so ).

Last edited by cxdoo; 11-30-2015 at 01:16 AM.
11-30-2015, 05:28 PM   #13
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Here's a photo of my setup if you're interested - been meaning to post it here for a while.


11-30-2015, 10:06 PM   #14
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One thought for something to look for/at
The old Omega enlargers (C600?) had a rig that you allowed you to remove the enlarger head, and mount a camera on it, Then use the enlarging lens as your optic, and the inverted enlarger head on the baseboard as a light source. The negative carrier could be used to keep the film flat.
Could be some cheap deals in old enlargers out there, may take some searching for the right one
Finding the camera adaptor plate accessory to go on the head could be a challenge (I think it needed a T-mount for the body), likely want an enlarger lens greater than 50mm to work with too,

With some other lights, could double as a stand for copying flat art or photo prints you don't have the negatives for.
Too many ideas probabaly
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