Enlarging Lens advice needed for 4x5...

[ic-racer]

Yes, a Rodagon, 120 WA.

I suspect that will be a fine lens. One thing to watch is that as an enlarging lens gets closer to the negative (like a shorter focal length, or as you make a bigger enlargement and bring the lens closer to the negative as you focus) the angle of the rays at the edges of the frame make the light mixing box opening seem smaller in relation to the negative. I know that my 4x5 mixing box just barely covers a full 4x5 negative with a 150mm lens.

Based on that I would predict on MY SYSTEM to use a wide angle 120mm lens for 4x5 I'd need to use the 5x7 mixing box if I wanted to make big enlargements full frame and show the rebate.

 

[darkroom_rookie]

The diffused-light working surface of the mixing box in my enlarger measures exactly 6 x 5 1/4" inches. The box was recently completely re-lined by myself with new high-quality polystyrene sheets.

 

[dpurdy]

My anecdotal experience 6 pages into this thread:

I used to have all my lenses in the silver barrel componon... 50 80 105
One started to grow fungus and I ran into a chance to replace all of them with the single coated Nikkors
I was surprised to see that the Nikkors were quite a bit contrastier and the grain was sharper in the grain focuser.

I also used to use a Rodenstock 135 for 4x5 and was annoyed for years that I had to burn the corners down for 16x20s.
I replaced it with a 150 Componon-S and now there is no need to burn corners at all.
It seems to me that the tonality is smoother and less contrasty with the 150 Componon-S than the shorter Nikkors.
I replaced 2 of my Nikkors with the multi coated newer variety and can't personally see a difference from the single coated ones.. I print black and white


Dennis

 

[ic-racer]

The diffused-light working surface of the mixing box in my enlarger measures exactly 6 x 5 1/4" inches. The box was recently completely re-lined by myself with new high-quality polystyrene sheets.

Very nice! My Omega 4x5 box measures only 5 1/8" square.

 

[ic-racer]

I also used to use a Rodenstock 135 for 4x5 and was annoyed for years that I had to burn the corners down for 16x20s.
I replaced it with a 150 Componon-S and now there is no need to burn corners at all.

Interesting. That Rodenstock was probably not a Rodagon, correct?

Within the Schneider line there is only 2.5% difference in falloff between the 135mm and 150mm Componon-S. That is one-sixteenth of a stop.

 

[Bill Burk]

Interesting. That Rodenstock was probably not a Rodagon, correct?

Within the Schneider line there is only 2.5% difference in falloff between the 135mm and 150mm Componon-S. That is one-sixteenth of a stop.

I thought the reason for using 150mm vs 135mm is that you don't go as near the edges of the coverage area. So even though two lenses may have the same falloff... You aren't getting into where falloff occurs.

p.s. I use a 135 Schneider Xenar 4.5 and while it may not be an APO, it serves my needs well enough that I am not looking for a replacement.

 

[ic-racer]

I thought the reason for using 150mm vs 135mm is that you don't go as near the edges of the coverage area. So even though two lenses may have the same falloff... You aren't getting into where falloff occurs.

p.s. I use a 135 Schneider Xenar 4.5 and while it may not be an APO, it serves my needs well enough that I am not looking for a replacement.

Bill, you know that the coverage of a lens is designed into the lens and is not an intrinsic function of focal length. If you compare the MTF and light falloff curves of the two mentioned Schneider lenses you see they have similar image circles at the same magnification.

Also, as you know, one is only using the far edges of the image circle when making enlargements at the lenses maximum recommended magnification. Otherwise, the lens should be functioning well within the image circle (that is one reason why 3 and 4 element lenses work well at small magnification but fail at large magnification).

 

[Bill Burk]

Bill, you know that ...

You give me too much credit. I don't know optics that well...

I just figured the coverage of different focal length enlarging lenses followed a progression (50 covers 35mm, 80 covers 6x6, 105 covers 6x9, etc)... And 135 nominally covers 4x5 while 150 covers some larger neg (5x7 maybe?).

 

[Leigh B]

The 135mm and 150mm lenses are awfully similar.

In fact, there is no 135mm in the Schneider Apo-Componon HM series, only 150mm.

That may be true of other product lines.

- Leigh

 

[RalphLambrecht]

the 150mm el nikkor is an excellent enlarging lens for 4x5. i have always enjoyed mine!

 

[voceumana]

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

Yes but you are grinding a super-cooled liquid, so it isn't quite the same as "machining" a solid. Glass flows. And "tar pitch" isn't my idea of a precision machining fixture. Maybe it is for you. Just because something is a "machine" doesn't mean it produces "machined parts", or why don't we call the prints we make from enlargers "machined prints"?
(Posted with all the seriousness that such a weightly academic topic deserves--or doesn't!)

Charlie

 

[ic-racer]

Glass flows.

Leigh is correct. Glass does not flow when it is in the super-cooled state. Read more here: http://www.glassnotes.com/WindowPanes.html

In May 1998, Zanotto wrote an article in the American Journal of Physics relating to the false notion that observations of thick glass in old windows translated to the fact that glass is a liquid. Zanotto sought to calculate the flow of glass and found that at 414 Celsius (777 °F) the glass would move a visible amount in 800 years, yet at room temperature he found that it would take glass 10,000 trillion times the age of the earth.

 

[Leigh B]

Yes but you are grinding a super-cooled liquid, so it isn't quite the same as "machining" a solid.

Grinding is the most precise and accurate of the standard machining methods.

Every high-precision part in industry, regardless of the material, is set to final form and dimension using grinding techniques.

- Leigh

 

[voceumana]

OK--I give up, none of my suggestions seem to explain why nearly all enlarging lenses have an element or elements that are not perfectly centered. Ctein reported this in an article for a Creative Camera Darkroom Guide (the article was on choosing an enlarging lens), and I trust his work.

To me, the reason why there are off-center elements doesn't really matter, what matters is that it exists. I believe Ctein did enough work on the subject to count as fact for me. And his statement that this occurs explains to my satisfaction why specific lenses seem to produce better images than others of exactly the same design, same model, same manufactuer.

Charlie

 

[Leigh B]

OK--I give up, none of my suggestions seem to explain why nearly all enlarging lenses have an element or elements that are not perfectly centered. Ctein reported this in an article for a Creative Camera Darkroom Guide (the article was on choosing an enlarging lens), and I trust his work.

Amazing how he finds so many problems that nobody else finds or reports.

Why would anybody trust his work?

All products in the world are manufactured to tolerances. This is a universal truth.
No product exists that is absolutely nominal in all respects. It's not physically possible.
So the question becomes: "How much deviation is acceptable?"

Manufacturers put considerable resources into investigating and answering that question,
and come up with production standards that reflect their desired level of quality.
They're interested in establishing the reputation of a product line in the market.

Ctein on the other hand is only interested in filling his wallet.

This tactic has been used forever. In the news business it's called "yellow journalism".
Find some nit, blow it way out of proportion, and create a perceived problem where none really exists.
The author has nothing to lose, since the whole idea is to get folks to read his work, regardless of its veracity.

- Leigh

 

[DREW WILEY]

Ctein is a friend of mine. I sometimes disagree with him about this or that, but know him well enough to recognize he actually does his homework and is not simply bluffing like so many other article writers. Some of his information about lenses etc is simply out of date, but possibly still relevant if
you're considering lenses of an appropriate vintage. Quality control varies less than it used to, at least among the major manufacturers in their upper-end products. Sometimes cheaper series of enlarger lenses have distinct quirks like focus shift at different f-stops. Quality control is NOT just
a matter of machine tolerances, which are not themselves always perfect, but of human assembly
of components too. But the odds of getting a bad modern lens from any of the big four is pretty low.

 

[Steve Smith]

Quality control is NOT just a matter of machine tolerances, which are not themselves always perfect, but of human assembly of components too.

And where the tolerance off of tooling is not accurate enough, other methods are used such as shims or matching an over sized part to a mating under sized part to cancel out the error.

However, I would think that a lens element would have to be off centre by a lot more than would be possible in even a very poorly machined housing to make any noticeable difference.


Steve.

 

[Leigh B]

Yes, there are many techniques that can be used in final assembly and in the preparatory
stages to minimize the effects of errors in individual components.
Reputable manufacturers (i.e. all of the major mfrs) take the time and expense to do that.

To say that the elements in a multi-element lens are "out of alignment" is gratuitous nonsense.

To take a moronically trivial case:
It is not possible to make a single plano-convex lens in which the optical axis is exactly coaxial with the physical axis.

Note that I said 'exactly'. It's easy to get the two axes quite close, but measurement techniques do not exist of sufficient
accuracy to make that alignment exact.

So saying that the elements in a multi-element lens are "off-center" is a tautology. It's true by definition, and completely irrelevant.
This is a typical example of blowing up a nothing into a cause celebre.

- Leigh

 

[DREW WILEY]

Just depends how fussy you need to be. As I've stated elsewhere, I cut my teeth on big precision
Ciba prints, so became pretty damn nitpicky about enlarger lenses. I also made very precise 8x10
dupes as part of the workflow, which needed a different category of enlarging lens. That being said,
there were still plenty of relevant choices. And anyone making reasonable-sized black and white prints would be like a kid in a candy shop right now, there are so many bargains out there, unless you're after something distinctly rare, like an Apo El Nikkor - which is too heavy for many typical
enlargers anyway, and sheer optical overkill.

 

[polyglot]

Alignment is an issue, though a rare one and only really with certain designs. Mass-manufacturing techniques got a lot better in the 90s, concurrently with improvements in software for the optimisation of optics. The result we see is that complex designs (zooms mostly) that were not previously commercially feasible due to rejection rates due to poor alignment suddenly became a lot more workable. Some optical designs are more sensitive to alignment (both radial and axial placement of an element) than others and we can now build the more-sensitive but higher-performing designs reliably.

For example, see all the 18-250mm crazy-zooms appearing for DSLRs with decent sharpness (though it seems manufacturers/consumers of those lenses care not for reducing distortion); they were not previously possible because of the assembly tolerances required. And they're hugely contentious on the digital forums because very poor examples slip through QA somehow and cause a lot of angst - you get people saying "mine is pixel-perfect sharp" and posting images while others are saying "but no this lens is shit" and posting images.

If you think of a graph of lens performance (in whatever dimension: resolution, contrast, chromatic aberration (CA), coma, etc) vs alignment error, it's going to be a peak with a drop-off to either side. Some designs have broad flat peaks therefore are easy to manufacture, other designs have a performance/alignment function that looks more like a thumbtack: a big spike with sudden dropoff. If there weren't this performance/alignment variability, we wouldn't be seeing sample-to-sample performance variability on brand-new lenses.

That said, enlarger lenses tend to be very much of the older robust designs that are easy to manufacture. While there is some sample variation, they still tend to be diffraction-limited and with little lateral CA; the APO versions have reduced CA. Enlarger lenses are not ultrazooms and they are not complex. While I'm sure you can find an occasional Really Bad one, it's not common and not nearly as bad as the sample variation seen on the really complex new designs.

 

[Mark Fisher]

Back to the original question.....Any of the quality name, modern 150 or 135 will be fine. In my experience there is more variation between lenses. Unless your enlarger is well aligned, I'm not sure how you could know a see any difference anyway. I am happy with my 135 componon s. If it has light fall off, I see that as a feature since I like to darken the edges subtly anyway.

 

[ic-racer]

That said, enlarger lenses tend to be very much of the older robust designs that are easy to manufacture. While there is some sample variation, they still tend to be diffraction-limited and with little lateral CA; the APO versions have reduced CA. Enlarger lenses are not ultrazooms and they are not complex. While I'm sure you can find an occasional Really Bad one, it's not common and not nearly as bad as the sample variation seen on the really complex new designs.

Real life example to demonstrate the point. I had inadvertently mis-seated one of the rear elements of a HM APO Componon during re-assembly. I'd say it was almost 0.5mm sideways. Six months later I decided to use the lens and was perplexed that the projected image was not side-to-side sharp after the laser alignment. I went and re-aligned the lensboard based on edge-to-edge sharpness with the Peak-1 magnifier. The results were surprisingly good and gave good prints during the printing session. To show how far off it was, laser beam needed to be about one centimeter off center to get the best print. Surprisingly all the prints (about 5x magnification) from the session were sharp, none needed to be re-printed.

My conclusion is that a significantly mis-centered enlarging lens can be used if one aligns the lens so all 4 corners are sharp with the Peak-1, rather than making the lens barrel perpendicular to the baseboard.