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Enlarging Lens advice needed for 4x5...

1. The rule of thumb for focal length being equal to the diagonal of the format is based on taking lenses at infinity. Lenses used at closer than infinity (i.e., greater bellows distance) can be shorter.

2. Four versus 6 elements: I'd rather have a 4 element lens perfectly aligned than 6-elements with some elements off center. Some 4 element lenses are of low cost design; others, notably the El Nikkor 50mm, and the Schneider Comparons (no longer being manufactured) are excellent performers when used at their designed magnification ratio. I have a nagging suspicion that some of our preferences for specific lenses come down to specific examples, where the alignment is exactly right tested against other examples where the alignment is off a little.

Charlie Strack
 
voceumana said:
1. The rule of thumb for focal length being equal to the diagonal of the format is based on taking lenses at infinity.
Click to expand...
The FL v. film diagonal is only a guide for selecting a focal length that will give a roughly "normal" angle of view.
It has nothing to do with lens performance, image circle diameter, FFL, or any other operating parameter.

voceumana said:
I'd rather have a 4 element lens perfectly aligned than 6-elements with some elements off center.
Click to expand...
None of the major manufacturers would ever sell a lens "with some elements off center".
Lens centering is very easy (thus inexpensive) to accomplish on a production line.

- Leigh
 
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ic-racer,

I'd be very interested to know if the charts below can give more insight on the lens' performance.
Especially if this lens is a good performer at 15x.



Thanks.
 
Want the Rolls Royce? Take out a second mortgage and buy a 210 Apo El Nikkor, if you can find one
and your enlarger will even support the weight of this kind of lens. But this is sheer overkill for any
ordinary use. Second choice -an ordinary Apo Nikkor; but at a max aperture of f/9 and shortest avail
FL for 4x5 also 210mm, not always practical. So then you're left with ordinary EL-Nikkors, etc - still
damn good. My mid-budget favorite is the Apo-Rodagon N 150. These turn up from time to time and
conspicuously outperform the herd. But unless your enlarger is precisely aligned on every plane, and
you are using a good glass carrier to keep the film consistently flat, none of this means much anyway.
 
15X and you're approaching the realm of the Rodagon-G, a specialized lens for large scale magnification, and not really intended for general work.
 
DREW WILEY said:
My mid-budget favorite is the Apo-Rodagon N 150.
Click to expand...

Two of these just went for $399 each on ebay...I was tempted but they have the same optimum 6X mag as the vanilla flavored Rodagon 150mm. At 6x from 4x5, that is a 24" x 30", out of my reach until I can get a bigger home to build a proper darkroom in and use a drop table with my 45MXT. Add to that the front is bigger and longer and I would have to re-design my contrast filter holder or use larger ones in between the light source and neg, a big no-no if you do split grade printing not to mention inviting more possibility of dust.

I also have the 135mm Rodagon for 20" x 24" without needing a drop table, the largest size I can practically do until I get a larger pad.
 
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DREW WILEY said:
15X and you're approaching the realm of the Rodagon-G, a specialized lens for large scale magnification, and not really intended for general work.
Click to expand...

15X from 4 x 5 is a massive 60" x 75", bigger than the largest roll paper currently available which is 56", that is getting to the size of Avedon's show "In the American West".

I think it is safe to say at that scale you would be well advised to have made a dedicated mural enlarger with the supporting roll paper dispenser and wet side system.
 
Leigh B said:
None of the major manufacturers would ever sell a lens "with some elements off center".
Lens centering is very easy (thus inexpensive) to accomplish on a production line.

- Leigh
Click to expand...

Barry Thornton in The Edge of Darkness reports receiving just such a lens: a Componon S with an element that was not centered when shipped from the factory. OK--it's one element, not "some", but it's still a major manufacturer, and a high-end lens.

ALL manufacturing is done to some degree of tolerance, otherwise why does the ± symbol exist? And ALL manufacturer's produce some defective product from time to time. I've worked too long for manufacturers to believe that all production is perfect.

I've read other photographers who say lens-to-lens variation is substantial in examples that they have seen.

As to focal length and diagonal, yes, you are right--my brain slipped. Anyhow, my comment about actual focus (bellows) distance is true: the angle of view makes a bigger circle at closer distances than infinity (as in enlarging) because the lens is farther from the focus plane (and the subject plane, in enlarging). It also gets bigger as the lens is stopped down.

Charlie Strack
 
Hi Charlie,

I'm pretty familiar with measurements, tolerancing, standards, production methods, etc.
In fact I'm a journeyman Tool & Die Maker, and own and operate a commercial machine shop. I've worked as a calibration tech.
I'm also moderator of the Metrology section of the largest machinist forum in the world.

The problem with lens manufacture before the advent of computer-controlled processes was variation from one specimen to another.
With modern methods that has been virtually eliminated, and with that change the problem with centering is greatly diminished.

Of course it's possible to find an example of any product that at one end of the tolerance range.
In a properly defined system that end should be well within the acceptable performance limits for the product.

You'll certainly find more variation in products manufactured before the 'computer age', perhaps 30 or more years ago.

- Leigh
 
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One sometimes sees the old chrome-barrel Componon lenses for sale. The Componon-S was a real
improvement, but at the time probably not equal in quality control to the Rodagons coming off an allegedly newer assembly line. That was about thirty years ago; but since then, things have pretty much equalized between the respective manufacturers. But if one is nitpicky like me, different lenses have slightly different pros & cons, or different personalities, when it comes to specialized applications. And I suspect that many alleged "tests" for the performance of specific lenses have
failed to take into account numerous other variables, other than the lens itself, which affect performance at the projection plane. Lots of BS out there, just as with other kinds of lenses.
 
Leigh B said:
Hi Charlie,

You'll certainly find more variation in products manufactured before the 'computer age', perhaps 30 or more years ago.

- Leigh
Click to expand...

Leigh,

Ah, yes, this is very true for metal parts. But glass lenses are their own thing--they are still ground, as far as I know, using the ancient techniques--not sure how they size the diameter after grinding, so perhaps tolerance comes into play in that part of the process. Glass is not "machined". (Would that it were!)

As a side note, many of the older lenses were in beautifully machined and finished barrels. Now the outer barrel is usually plastic. Barry Thornton noted that on his Componon-S, I think it was, the plastic outer barrel split in two (along the lens axis). The inner metal barrel (which held the elements) was in tact, so some careful gluing.

Drew,

I concur with you--some specific examples of lenses seem to have a magic in how they create images that seems to defy technical measurements.

Charlie
 

Also note that the newer EL-Nikkors in most sizes are 6 elements in 4 groups. This includes the 135mm and 150mm EL-Nikkor "A" series, and most of the "N" series lenses from 50mm to 105mm. I believe only a couple f/4 aperture lenses of this series are 4 element Tessars.

There is no need to buy a new enlarging lens. The 135mm EL-Nikkors and even the 150mm lenses are readily available on ebay in new or almost new condition. You need not pay more than about $75 for one. Just make sure they are the N or A series from the '80s and up.
 
voceumana said:
Glass is not "machined". (Would that it were!)
Click to expand...
Hi Charlie,

Sorry to disagree, but glass certainly is machined, at least as far as the grinding process is concerned.

The grinder is a machine. It can be controlled by computer, and the results can be analyzed by automated measurement.
The results are used as input to the control system to fine-tune the position of the active tools (grinding surfaces).

This results in a much higher achievable uniformity than was previously possible.

- Leigh
 
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A Minox negative 8x11 mm requires more magnification that any other format to get a practical size print. The lens supplied with the Minox enlarger is a 4 element Tessar. The Tessar formula is capable of producing high quality images. Its main limitation is that the maximum aperture is restricted to about f2.8. There are many factors which contribute to making a particular formula a good lens. The number of elements is only one factor. It must be remebered that each additional element in a lens causes a reduction in contrast of the image. Until the invention of lens coating this effect seriously limited lens design. The loss of contrast can be reduced but never completely eliminated. One of those incovenient gotchas of the laws of optics.
 
Gerald C Koch said:
There are many factors which contribute to making a particular formula a good lens.
The number of elements is only one factor.
Click to expand...
I was talking about real lenses, as in products available from manufacturers.
My comments were not about academic exercises in a college optics design class.

Manufacturers of enlarging lenses frequently had two product lines, one of four elements and one of six.
The latter were of much higher quality, with tighter quality control and better corrections, as reflected in the higher price.

Many cheaper four-element designs were available from various manufacturers, some quite reputable, others less so.

The Minox was never recognized as a standard of image quality.

- Leigh
 
Hi Leigh,

The laws of optics do apply to real lenses. However, let's agree to disagree.

Jerry
 
Hi Jerry,

And the laws of economics trump the laws of optics when it comes to deciding what's available in the marketplace.

As I said previously, my comments were comparisons of actual products on the street, not on what was or was not possible.

- Leigh
 

You're sticking filters under the lens? They will affect your sharpness significantly more than any choice of enlarger lens you might make.
 
polyglot said:
You're sticking filters under the lens? They will affect your sharpness significantly more than any choice of enlarger lens you might make.
Click to expand...

I strongly disagree. Poor lens choice will result is blurry corners or lack of complete coverage.
Using a Peak 1 grain focuser I cannot detect any change in grain sharpness with an Ilford MG acetate filter in the light path below the enlarger light.
 
I have a Componon 150mm f 5.6. What is the difference between this and a Componon S?


Steve.
 
ic-racer said:
The makers of 135mm enlarging lenses for 4x5 film have not heard of your rule.
Click to expand...

They're going to be really annoyed when they do!


Steve.
 
darkroom_rookie said:
ic-racer,

I'd be very interested to know if the charts below can give more insight on the lens' performance.
Especially if this lens is a good performer at 15x.

View attachment 55964

Thanks.
Click to expand...

The MTF shown (Rodagon?) demonstrates excellent performance at 6x. I suspect it would also be good at 15x but that is based on my experience with the usual 6-element lenses commonly used and not based on any info in the chart presented.
 
ic-racer said:
The MTF shown (Rodagon?) demonstrates excellent performance at 6x. I suspect it would also be good at 15x but that is based on my experience with the usual 6-element lenses commonly used and not based on any info in the chart presented.
Click to expand...

Yes, a Rodagon, 120 WA.
 
I have a Componon 150mm f 5.6. What is the difference between this and a Componon S?


Steve.
Click to expand...
This chart shows the technical differences. This particular chart is from a point in time when they still made both types. Both are 6 element.
I have quite a few of both but only matching focal lengths in 150mm and 80mm to compare side-by-side. I cannot detect any difference in prints but I do not have any MTF curves of the non-"S" lenses to post for a true objective comparison.
 
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