Medium format enlargements with 50mm instead of 75mm lens

alex millman · May 6, 2014

Yesterday i made some enlargements of medium format film with a 50mm lens instead of the correct 75mm lens. I did not notice any difference in my prints. My question is: is it really necessary to change lens when changing formats? I am using a durst AC707 autocolour enlarger with 645 negatives shot on a bronica. Both lenses are nikon.

BMbikerider · May 6, 2014

I do believe that Nikon enlarging lenses are reputed to have a greater coverage than they are designed to be used with, which may be the answer. However I would contend that a Nikkor 80mm F5.6 gives better edge sharpness than the 50mm Nikkor if the prints were examined closely.

BMbikerider · May 6, 2014

I do believe that Nikon enlarging lenses are reputed to have a greater coverage than they are designed to be used with, which may be the answer. However I would contend that a Nikkor 80mm F5.6 gives better edge sharpness than the 50mm Nikkor if the prints were examined closely. Especially if the enlargement were 12x9.5 or larger.

MattKing · May 6, 2014

If you have a 50mm lens on your enlarger that gives even, sharp coverage over your entire 645 negative, then it will work fine.

In most cases though, a 50mm enlarging lens used for a 645 negative will result in lighter, unsharp corners in a print made from the full 645 negative.

ic-racer · May 6, 2014

The coverage of all enlarging lenses is enhanced at low magnification. In fact when you get to the range of reductions, you can use a lens with a focal length equal to the diagonal of the print, even if the negative is much much larger.

cliveh · May 6, 2014

Use a 80mm.

Tom1956 · May 6, 2014

I'd use the 75 or 80, if for no other reason than to preclude light fall-off from center to corner.

polyglot · May 6, 2014

The sharp region is smaller than the lit region, so you will see corner softness earlier than you would with the correct lens. Consider the coverage to be a cone extending out of the lens - if the lens is further from the film (due to you making a small print) then clearly you can print a larger piece of film. This is why a too-short lens will work fine to print a 5x7 print but will fail horribly if you try to print a 16x20.

RalphLambrecht · May 6, 2014

the cone is a good metaphor.I may steel that one day if that's ok?

polyglot · May 7, 2014

of course, but I'm sure there's a diagram to exactly that effect in your book...

Thomas Bertilsson · May 7, 2014

alex millman said:
Yesterday i made some enlargements of medium format film with a 50mm lens instead of the correct 75mm lens. I did not notice any difference in my prints. My question is: is it really necessary to change lens when changing formats? I am using a durst AC707 autocolour enlarger with 645 negatives shot on a bronica. Both lenses are nikon.

If you see no quality difference, then use whatever lens you like to use. Whatever theory exists that it doesn't work doesn't matter, because it obviously does work for you.

I have a dedicated 35mm enlarger, so I can't do what you do, but for negatives from 6x9 to 645 I use the same 100mm lens. Keeps it simple. I can't go the other way like you do, though, and use my 80mm Minolta Rokkor lens on 6x9 negatives, because it will not cover evenly. So I think you're lucky to have a 50mm lens that also covers 645.

pentaxuser · May 7, 2014

Interesting thread. I have a 50mm El Nikkor but always move to a Rodenstock 80mm for my 645 negs, simply because of what I have read here on APUG and in books. However most of my prints are 5x7 with occasional 8x10 so I'll give the 50mm a try next time and see what happens.

pentaxuser

ic-racer · May 7, 2014

pentaxuser said:
Interesting thread. I have a 50mm El Nikkor but always move to a Rodenstock 80mm for my 645 negs, simply because of what I have read here on APUG and in books. However most of my prints are 5x7 with occasional 8x10 so I'll give the 50mm a try next time and see what happens.

pentaxuser

Using a short lens causes many more problems that it solves; no good can come of it. Perhaps that wasn't clear in this thread. For example:

more cosine falloff
smaller effective light box opening compared to the negative
condenser needs to be adjusted for the lens, not the film format; light may not cover
risk of inadequate corner sharpness
50mm lens may not focus on a Medium format or large format enlarger without a recessed lensboard

Thomas Bertilsson · May 7, 2014

ic-racer said:
Using a short lens causes many more problems that it solves; no good can come of it. Perhaps that wasn't clear in this thread. For example:

more cosine falloff
smaller effective light box opening compared to the negative
condenser needs to be adjusted for the lens, not the film format; light may not cover
risk of inadequate corner sharpness
50mm lens may not focus on a Medium format or large format enlarger without a recessed lensboard

How do you think the Leica 40mm Focotar lens fits into all of this? I get at least the same quality from it that I get from a 50mm EL-Nikkor, Rodenstock, or Schneider 50mm.
Just curious.

Ian C · May 7, 2014

A 40mm enlarging lens that is SPECIFICALLY DESIGNED for 35mm format works fine for that purpose.

I use sub-format lenses specifically designed for the format they are intended for: 40/4N EL Nikkor for 35mm format, 60/4 Rodagon WA for the 6 x 4.5cm up to 6 x 7cm formats, and 120/5.6 Rodagon WA for the 4” x 5” format. Each lens works perfectly for its intended format and within the maker’s stated magnification range. There is also an 80/4 Rodagon WA intended for the 6 x 9cm format. In my experience, these produce prints identical to the normal focal length lenses for each format.

The original question is different. It involves using a lens that is not only shorter then usual for the format, but more importantly, one that is NOT SPECIFICALLY DESIGNED for the format on which it’s used. It won’t properly cover larger formats at all practical magnifications. This is most noticeable at large magnifications.

It might work acceptably at small magnifications where the lens is far enough from the negative so that the film is fully covered by the lens’s circle of good definition as defined by the lens maker (most often specified by the maker as the lens’s coverage angle). The projection that extends outside of the maker’s stated coverage angle falls off radially in both definition and illumination and is considered unusable for high-quality results.

ic-racer · May 7, 2014

Thomas Bertilsson said:
How do you think the Leica 40mm Focotar lens fits into all of this? I get at least the same quality from it that I get from a 50mm EL-Nikkor, Rodenstock, or Schneider 50mm.
Just curious.

40mm is only 3 mm wider than normal. I don't see any issues.

MattKing · May 7, 2014

I've found that my 60mm Focotar works well with both my 35mm negatives, and my 645 negatives.

And it is way easier to focus on my Omega D6 than my otherwise good quality 50mm lenses.

dynachrome · May 7, 2014

I used a 50/4 EL Nikkor for many years with a Bogen 22A Special. My standard lens for 6X6 was an 80/5.6 EL Nikkor but a few times I printed the 6X6 negatives with the 50/4. As long as I was printing at least 8X10 the combination of the lens and the condensers worked. The 50/4 never got much respect but stopped down a little it was quite good. A faster lens like the 50/2.8 EL Nikkor might be sharpest close to wide open but I always felt that closing down a little more gained me more leeway with a possibly slightly out of adjustment enlarger than I lost from diffraction.

Thomas Bertilsson · May 8, 2014

ic-racer said:
40mm is only 3 mm wider than normal. I don't see any issues.

That's the point I wanted you to make. And also consider whether the lens was designed for the job or not.

It's still interesting to me that the OP is getting good prints (to their eye) from a lens that technically shouldn't be capable of it, don't you think? I'm stunned by it in fact.

dorff · May 8, 2014

Thomas Bertilsson said:
That's the point I wanted you to make. And also consider whether the lens was designed for the job or not.

It's still interesting to me that the OP is getting good prints (to their eye) from a lens that technically shouldn't be capable of it, don't you think? I'm stunned by it in fact.

I agree, it is interesting. I print 35 mm with a Durst M605 fitted with a 50/2.8 EL-Nikkor in a recessed retainer, and change to a Rodagon 60/4.5 for 6x4.5 and 6x6. I would not print medium format with the 50 even if I could, because the head height would be too low for my liking. If you have multiple boards or retainers, use them. It makes it quick and painless to switch over.

ic-racer · May 8, 2014

Thomas Bertilsson said:
That's the point I wanted you to make. And also consider whether the lens was designed for the job or not.

It's still interesting to me that the OP is getting good prints (to their eye) from a lens that technically shouldn't be capable of it, don't you think? I'm stunned by it in fact.

Looking back at all my prints from my 'teenage years' nearly all the corners are blurry from either poor enlarger alignment, improper aperture selection, poor lens or some combination of those conditions. At the time I thought the prints were 'great'.

Thomas Bertilsson · May 8, 2014

ic-racer said:
Looking back at all my prints from my 'teenage years' nearly all the corners are blurry from either poor enlarger alignment, improper aperture selection, poor lens or some combination of those conditions. At the time I thought the prints were 'great'.

Which is exactly why I wrote 'in their eyes'. I look at my old prints also wondering why I thought they were wonderful. Not that unsharp corners necessarily makes it a poor print, but it's something I too believe should be avoided.

Anyway. To me it's not much work to put the correct lens in the enlarger, and it is probably preferably to use an enlarging lens as it was intended to be used.

Medium format enlargements with 50mm instead of 75mm lens

alex millman

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Thomas Bertilsson

Medium format enlargements with 50mm instead of 75mm lens

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