Enlarging Lenses - Optimum Magnification

H. G. Hart · Sep 28, 2008

I'm looking for information on enlarging lenses' range of magnification and optimum magnification.

So far I have only found concrete data for Rodenstock lenses. I'm interested in any data for the 240 and 300 mm Componon-S and 240 and 300 mm El-Nikkor lenses, though I realize data for the El-Nikkors may be non-existent.

The only Schneider literature I have states a magnification range of 2-20:1 for the Componon-S lenses (an optimum magnification is not given); I suspect this is true for shorter lenses (i.e. 80mm) but inaccurate for lenses over 210mm which might have a range closer to 2-10:1. The G-Componon data sheet I have gives a range of 15-40:1 with optimum magnification at 20:1. In both cases the figures are for the entire group of lenses, not individual focal lengths.

Thanks for your help.

Mick Fagan · Sep 28, 2008

I don't believe Schneider have ever given out any absolute magnification factors, concerning where their enlarging lenses are positively focused.

However if you work backwards on the basis of 12x16" or 40x50cm paper enlargements, with slight cropping to have a borderless print, then you should be close to the optimised enlargement magnification factor for most format sizes.

The 12x16" paper size is the most common size used after 8x10" paper and the one size in the middle of two other of the most used paper sizes internationally, 8x10" and 20x16".

I have three Componon S lenses, 50 to 150, I believe that they all work best at or around 12 to 17 times magnification with their optimal being around 14 to 15 times magnification factor. My 150 lens though, probably works best at or around 5 to 8 times enlargement

35mm works well on either 8x10", A4 (best) and/or 12x16" paper. 4x5 works well on either 12x16" and/or 16x20". 8x10" works well on 16x20" or 24x30" paper.

These are the paper sizes that those formats were mainly enlarged to, therefore most enlarging lens manufacturers would ensure that their lenses worked well at these magnification factors. If they didn't perform with these paper sizes, then people would have stopped buying them.

Mural sized enlargements, are another matter.

Mick.

resummerfield · Sep 29, 2008

Here are 2 scans from a 1983 Nikon El Nikkor Enlarging Lens brochure. It features the older lenses, but I think the later N lenses have the same construction. In my experience older and newer 300 El Nikkors seem to have identical interior construction, and performance.

I scanned these at a high resolution, but the attachment process of this forum reduced the resolution.

ic-racer · Sep 29, 2008

H. G. Hart said:
The G-Componon data sheet I have gives a range of 15-40:1 with optimum magnification at 20:1. In both cases the figures are for the entire group of lenses, not individual focal lengths.
.

Looking at this datasheet it does look to me like even the very long G-Componons are optimized for 20:1 enlargement. The chart does not list data for anything less than 15:1 enlargements for the whole G-Componon series.

http://www.schneiderkreuznach.com/archiv/pdf/g_componon.pdf

The 300mm Rodenstock I am using now is claimed to be suited for 2x-8x optimized for 4x. I know from experience that it does develop a distinct curvature of field when at 1:1 and doing reductions. This makes me think those G-Componon 300mm lenses may be unsuitable for home darkroom use. Perhaps tinkering with the element spacing could re-optimize them to 'more human' 2x to 4x (which is, of course 16x20 to 32x40).

Martin Aislabie · Sep 29, 2008

Don't enlarger lenses (good ones) even when used well away from their optimum out resolve photographic paper by large factor

Unless you are doing something realy huge isn't the limiting factor the paper you print on ?

Martin

ic-racer · Sep 29, 2008

Martin Aislabie said:
Don't enlarger lenses (good ones) even when used well away from their optimum out resolve photographic paper by large factor

Unless you are doing something realy huge isn't the limiting factor the paper you print on ?

Martin

In some cases, you are correct. However, one problem is the effective apertures used in enlarging lower the resolving power to near that of paper. ie 20x enlargement at f8 = f168.

H. G. Hart · Sep 29, 2008

resummerfield said:
Here are 2 scans from a 1983 Nikon El Nikkor Enlarging Lens brochure. It features the older lenses, but I think the later N lenses have the same construction. In my experience older and newer 300 El Nikkors seem to have identical interior construction, and performance.

I scanned these at a high resolution, but the attachment process of this forum reduced the resolution.

Thank you, this was extremely helpful.

For posterity here is my own anecdotal information on Rodagons:

At three times magnification the 300 mm Rodagon is obviously sharper than the 300 mm Rodagon-G; at 8:1 the Rodagon-G becomes somewhat sharper. I've never had occasion to make an enlargement bigger than 64x80". This corresponds with data sheets I have that give a range of 2-8:1 for the Rodagon and 8-30:1 for the Rodagon-G.

I'd be interested to make comparison prints for the 240 mm El-Nikkor, 240 mm Rodagon and 240 mm Componon-S at 3:1 (the size I most commonly print at).

Martin Aislabie · Sep 30, 2008

I have a 150mm Rodagon-G and have wondered where the "sweet spot" is on the enlarging lens

I know they were designed for large enlargements (hence the G for grand) but I am unsure how large is normal and how large is grand

For a 150mm - is it also (as H G Hart suggests for a 300mm) at 8 to 20 times enlargement ?

Thanks

Martin

H. G. Hart · Sep 30, 2008

Martin Aislabie said:
I have a 150mm Rodagon-G and have wondered where the "sweet spot" is on the enlarging lens

Rodenstock gives 10-40:1 as the range of magnification for the 150 mm Rodagon-G (20:1 is the optimum magnification).

ic-racer · Sep 30, 2008

Martin Aislabie said:
I have a 150mm Rodagon-G and have wondered where the "sweet spot" is on the enlarging lens

Check the table at the bottom of this page, column "3"

http://www.prograf.ru/rodenstock/enlarging_en.html#Rodagon-G

Like stated in the OP, I have never seen a similar table for the Schneider lenses.

Martin Aislabie · Sep 30, 2008

ic-racer, thanks for the info and the link

The amount of knowledge that is available through APUG is just staggering

I had looked through the Rodenstock web-site several times but never found that page.

H. G. Hart – can you really spot a significant difference in the sharpness of Rodagon-N & Rodagon-G prints at 3 to 5 times enlargement (for me that’s 12x16 up to 20 x24) ?

Many thanks

Martin

H. G. Hart · Sep 30, 2008

Martin Aislabie said:
H. G. Hart can you really spot a significant difference in the sharpness of Rodagon-N & Rodagon-G prints at 3 to 5 times enlargement (for me thats 12x16 up to 20 x24) ?

In my experience, yes, but let me describe the exact circumstances of my comparisons.

First, I have only compared these lenses in the 300 mm focal length. Second, I have only compared them at 3:1 and 8:1 magnifications. Third, I find these lenses sharpest at f/5.6-8. Any difference in sharpness seems to decrease proportionately with aperture regardless of whether the magnification is 3:1 or 8:1.

Anecdotally, the difference in sharpness between the two lenses was obvious at 3:1 with an aperture of f/5.6. The difference between the lenses was less significant at 8:1, but the Rodagon-G was sharper.

I suspect the Rodagon will quickly lose ground to the G as enlargement increases. I can't imagine that many photographers reach the optimum magnification of 20:1 with the 300 mm Rodagon-G. I suspect this lens was intended more for the graphics industry.

Martin Aislabie · Oct 1, 2008

The Data sheet combined with H G Harts anecdotal evidence leads me to think I have bought the wrong lens for the task

I will have to invest in a Rodagon-N to get the best out of negs/prints with the sizes I can print - which realistically is a max magnification if X5 - a long way short of where a Rodagon G hits its stride

However, I will make do with what I have at the moment and put a Rodagon-N on my not inconsiderable "would like to have" list

Thanks for the help guys

Martin

H. G. Hart · Oct 1, 2008

Martin Aislabie said:
However, I will make do with what I have at the moment and put a Rodagon-N on my not inconsiderable "would like to have" list

Let us know your results if you ever have an opportunity to compare the two lenses.

Martin Aislabie · Oct 2, 2008

H. G. Hart said:
Let us know your results if you ever have an opportunity to compare the two lenses.

No problem

Its a little questionable - comparing individual lenses - I am sure there is more variation unit to unit than we all care to admit.

However, I always like to do these sort of exercises - for my own benifit - have spent my hard earned money well or blown it chasing the unattainable

Martin

R W Penn · Oct 2, 2008

I have 50 N & 80mm N which are better than 80 WA and 50 G up to 11X Then the G is better.Also have a 120mm WA "new" that I dont use.

nworth · Oct 4, 2008

While there is usually an optimum magnification, most modern lenses perform well over a wide range. Note that Schneider says its Componon-S is designed for magnifications of 2 to 20, a wide range. They mean it. The optimum will vary from lens to lens. If it is not listed, think of the design criteria. Lenses for smaller formats (50mm, 75mm) will be designed to produce good 8X10 or maybe 11X14 prints from 35mm or 6X6 negatives. 135 and 150mm lenses will have to work with this size of enlargement, too, but may be designed to work best with somewhat larger enlargements, maybe 16X20, from 4X5 negatves.

Enlarging Lenses - Optimum Magnification

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