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02-06-2021, 11:04 AM   #1
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Extension Tubes and Macro 1:1 ratio

I was wondering how can I achieve 1:1 macro ratio with extension tubes. I want to "scan" my negatives with my Fuji X-T2 so I can save money.
The lenses I have are the following (all of them with the proper adapter):
-CANON FD 28mm/f2.8
-SUPER MULTI COATED TAKUMAR 50mm/f1.4
-SUPER MULTI COATED TAKUMAR 135mm/f3.5
I am more inclined to use the 50mm Tak but I am open to suggestions based on my gear.
SoI think the question is how many and which lenght of tubes do I need?

Thanks!

02-06-2021, 11:47 AM - 1 Like   #2
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1:1 (1.0x) requires extension equal to the lens focal length, so for your SMC Tak 50/1.4 you would need tubes totaling 50mm. Similarly, you would get 1:2 (0.5x) with 29.5mm extension.* Both assume the lens focus ring at the infinity position. In regards to focus, at magnifications 0.5x and higher, it is easier to focus by moving the lens-camera as a unit rather than fiddling with the focus ring.** This is most easily done with a focusing rail.

You can do the same with your other two lenses, but working distance with the 28mm will be very tight, while assembling sufficient tubes for the 135mm may difficult; a bellows for that lens would be a better solution.

Edit: I did not read closely enough to note the desire to digitize 35mm film negatives using an APS-C camera. For that case, the desired reproduction ratio would be 1:1.5 (0.67x) rather than 1:1 (1.0x). Using the 50mm lens, the required extension would be 38mm; something that may be accomplished with a little shorter tube (my set has a 32mm size) and some adjustment with the focus ring. Distance from the sensor plane to subject will be about 210mm.


Steve

* The actual calculation for other than 1:1 is a bit counter-intuitive
** Using the focus ring will affect the magnification more than the focus at greater than 0.5x.

Last edited by stevebrot; 02-07-2021 at 10:02 PM. Reason: put in correct information for digitizing 35mm to APS-C
02-06-2021, 11:55 AM - 1 Like   #3
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If you are interested in the technical aspects, I have found the set of articles at the link below to be helpful:

Coin Imaging | Optics Articles (meant to be read in order)


Steve
02-07-2021, 03:37 AM - 1 Like   #4
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QuoteOriginally posted by AnalogLuis Quote
I was wondering how can I achieve 1:1 macro ratio with extension tubes. I want to "scan" my negatives with my Fuji X-T2 so I can save money.
As your sensor is likely smaller than your negatives, you may need a smaller magnification (1:1.5). So a 35mm extension ring might be what you need, together with the lens' closer focus setting.

02-07-2021, 11:01 AM - 1 Like   #5
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QuoteOriginally posted by JensE Quote
As your sensor is likely smaller than your negatives, you may need a smaller magnification (1:1.5). So a 35mm extension ring might be what you need, together with the lens' closer focus setting.
This would be true if you want equivalent framing to 24x36mm FF, say for slide duplication, but is of little use for technical macro (e.g. coins, stamps, scale modes, etc.) where actual 1:1 to the sensor is more important.

As far as dialing in 1:1.5 (0.67x) with a 50mm lens, the required extension would be 38mm or perhaps a bit less with the difference made up using the focus ring.

Addendum: I was off-base on my initial comments above based on the thread title. OP is wants to copy 35mm film frames to APS-C, so the 1:1.5 ratio is appropriate.


Steve

Last edited by stevebrot; 02-07-2021 at 09:56 PM. Reason: Corrected math...again
02-07-2021, 08:35 PM - 1 Like   #6
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When doing near 1:1 repro with non-macro lenses, the quality of the results is not always predictable. Some lenses do well, others do not. The 50mm with tubes as described by previous responders is probably the best system. Consider covering a little bit more than the precise edges of your negatives, then cropping in PP. Also, when lighting your negatives


1) use diffused, reflected back lighting = bounce the lights off a white surface well behind the negative. This will reduce the chances of getting a central hot-spot, or to put it another way, will prevent substantial vignetting.

2) Try to make a set up where the back lighting of the negative is the only light in the workspace. Avoid having the back lights shining up toward the camera*, avoid any lights shining down on the negatives that might create reflections.

*This can cause a reflection of the camera off the surface of the negative which may appear as a faint ghostly image of the lens & camera in your scan.
02-07-2021, 09:03 PM - 1 Like   #7
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QuoteOriginally posted by WPRESTO Quote
When doing near 1:1 repro with non-macro lenses, the quality of the results is not always predictable. Some lenses do well, others do not.
I have puzzled over this and wonder if it has to do with field curvature. Dedicated macro and bellows lenses are designed to have very flat fields.


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02-07-2021, 09:20 PM - 2 Likes   #8
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Aberration correction is dependent on magnification - i.e. angles. Field curvature is likely not a serious issue for lenses based on a symmetric construction (double-Gauss) like the 50/1.4.
02-08-2021, 04:45 AM - 1 Like   #9
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QuoteOriginally posted by stevebrot Quote
I have puzzled over this and wonder if it has to do with field curvature. Dedicated macro and bellows lenses are designed to have very flat fields.Steve

I will make no claim to have any but the most elementary understanding of optics, the "why" of optical phenomena, but I do know some actualities. Lens formulae have an ideal ratio of subject-to-lens vs lens-to-image-plane distances. This is most obvious in deep macro lenses, those designed for reproduction ratios above life size. There is an optimum magnification for these,. At either lesser or greater magnifications overall IQ declines. They are totally unsuitable for use at infinity, or even ordinary close-up range such as 1/5 life size. It has been common knowledge that when photographing something at greater than life-size with a regular camera lens, it's worth trying the lens in reverse position to improve IQ. This is because of the subject-to-lens versus lens-to-image-plane ratio. At greater than life size the lens is acting like a projector lens. The Tessar four-element lens is surely one of the great basic lens designs. At one time some manufacturers offered "macro-Tessar" lenses in which, you guessed it, the sequence of Tessar elements is reversed.

Flat field is generally desirable in ordinary camera lenses just in case there is something at the edge or in the corner of an image that should be sharp. Flat fields in macro lenses, those used in the range of perhaps 1/10th life size to life size, was originally regarded as desirable because these lenses were once commonly used for copying documents or photographs or paintings. The 4-legged copy stand devices that threaded into a filter thread is evidence of this as such a device was not intended for photographing insects, flowers and the like, what most of us use our macros to do. When photographing flowers or insects close-up, the subject is not "flat field." In fact, the periphery of the image field for such subjects is commonly background where bokeh is far more important than flat-field sharpness, and fortunately, most macro lenses have excellent bokeh.

I am sometimes surprised that acutance has dropped out of lens evaluation. It probably has a much greater impact on the impression of IQ than field curvature.

Last edited by WPRESTO; 02-08-2021 at 04:51 AM.
02-08-2021, 09:11 AM   #10
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Wow!! I am grateful for all the information provided by all of you, a lot of knowledge that is more than welcome. Didn't know macro lens vs regular lens with tubes would have such an impact on IQ.
02-08-2021, 12:54 PM - 1 Like   #11
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QuoteOriginally posted by AnalogLuis Quote
Didn't know macro lens vs regular lens with tubes would have such an impact on IQ.
It might...it might not. For slide duplication, I would give it a try with what you have and if the results are not as good as expected, then a dedicated macro lens or a different 50mm might be an option.


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02-08-2021, 02:13 PM - 1 Like   #12
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QuoteOriginally posted by stevebrot Quote
It might...it might not. For slide duplication, I would give it a try with what you have and if the results are not as good as expected, then a dedicated macro lens or a different 50mm might be an option.Steve
I agree 100% with stevenbrot's advice. Always experiment with what you have and see how it works. BTW: Don't expect your digital conversions to look as good as the originals. In my experience, there is always some loss of something - detail, color balance, tonal range, something. Also, be prepared to deal with the Dust Devil. There is no way to get a chrome or negative free of dust before digitizing.
02-09-2021, 05:16 PM   #13
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QuoteOriginally posted by WPRESTO Quote
I agree 100% with stevenbrot's advice. Always experiment with what you have and see how it works. BTW: Don't expect your digital conversions to look as good as the originals. In my experience, there is always some loss of something - detail, color balance, tonal range, something. Also, be prepared to deal with the Dust Devil. There is no way to get a chrome or negative free of dust before digitizing.
I'll give a try. Would you suggest a dedicated scanner instead? I've seen multiple videos and read reviews with mixed opinions, but all of them leaning towards DLSR/APS-C scans being better than photography scanners like EPSON V's.



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02-10-2021, 01:49 AM   #14
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QuoteOriginally posted by AnalogLuis Quote
I agree 100% with stevenbrot's advice. Always experiment with what you have and see how it works. BTW: Don't expect your digital conversions to look as good as the originals. In my experience, there is always some loss of something - detail, color balance, tonal range, something. Also, be prepared to deal with the Dust Devil. There is no way to get a chrome or negative free of dust before digitizing.
+1 on working with what you have. On the 'look as good' - that may be the case for 'perfect' slides. But I definitely was able to post-process things so that they print better than from slides and correct things like an odd color cast, where the result on screen look at least as good as the projected original. Dust is indeed a huge problem, that's easily ignored when you project, but isn't in the transformation process.

That said, I've seen professionally scanned and cleaned up private slides from the 60s through the 80s (most of it east German Agfa/Orwo color reversal film) recently, compared to which I would have to put in a lot of time to achieve the same result.
02-10-2021, 05:21 AM   #15
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QuoteOriginally posted by AnalogLuis Quote
I'll give a try. Would you suggest a dedicated scanner instead? I've seen multiple videos and read reviews with mixed opinions, but all of them leaning towards DLSR/APS-C scans being better than photography scanners like EPSON V's.



Luis
I used a Minolta Dimage II dedicated scanner to scan all 20,000 of mount film and slide shots. It was painfully slow, the project took about 5 years to complete,

I think, now, especially with a full frame body, a macro bellows setup with film copy attachment would be a better option. You might be able to find an old unit from the film era.
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