Procedures for testing/comparing large number of enlarging lenses?

[craigclu]

I have compared lenses in one vs another situations but I'm in a situation now where I've got a large number of things to review and cherry pick from. I've got good old standby glass that could serve me well and I'll likely remain with anyway (APO's in my primary focal lengths) but I also know that there are some jewels that can exhibit wonderful results. For instance, I have a favorite Rodagon 50mm 2.8 and Rodagon N APO 50 that I cannot discern differences between while a Componon S 50 was easily bested by both of these. I also know that three more examples of these lenses could return just the opposite result in comparison. Also, there are the subtle nuances that tend to favor certain styles of printing as I've got a favorite 90mm that adds a tonal gradation in mid-tones that gives added dimension to skin tones/people oriented work.

I recently came into a large number of enlarging lenses and it's troubling me to just peddle them off without giving them a run-through in case there's some "magic glass" among them. All together, I've got 29 decent lenses with what I currently had plus these new additions and frankly, I don't know where to start. I mounted and did a quick Microsight review on a few things and was talking myself in and out of interpreting grain sharpness with this method. Factors such as enlargement ratios, behavior with denser/less dense negatives (tonal renditions) multiplied so many times just have me confused. Is there a known, proven method for reviewing this sort of thing? Are there test negatives that would give valid comparison results that would be measurable/quantifiable? I imagine resolution via a target negative would be easy enough but contrast and "edgieness" between specific tones would be more difficult. Again, a simple comparison between a pair of lenses is one thing but this feels a bit overwhelming. I don't recall seeing this discussed and didn't turn up anything useful on my own.

 

[Phillip P. Dimor]

I'd find a test-negative for sharpness, or a negative that you know is sharp all over. I would also probably use the smallest size of enlarging paper that I have, 3.5x5" or 5x7" and would find the correct exposure for each length of lens, ie. 50mm, 75mm/80mm, 100/105mm, 135mm, etc.. I'd try to use f8 or f11. I'd then write w/ a sharpie on the back of each exposed piece the name of the lens, focal length, f-stop, exposure time.. Then evaluate each test print w/ a good loupe on a lightbox. I think you could do this relatively quickly in a week or so. I've never done this but I think this would be a good way to start. I'm sure there is a better way but who knows..

I think your major problem will be finding that 80% of your enlarging lenses are fantastically good and undistinguishable from each other. Thats my opinion atleast.

 

[Roger Hicks]

Dear Craig,

Leica tests camera lenses using a standard test negative and a modified projector. I'd suggest something similar.

Cheers,

R.

 

[Photo Engineer]

You need a standard definition chart such as I have shown in posts on the emulsion making and coating forum. This is made by several companies including Edmund scientific.

For best results, you need a negative and a positive chart to show bleed and fill.

PE

 

[craigclu]

For best results, you need a negative and a positive chart to show bleed and fill.
PE

I used to have the test negative that came with the old Bes-Align (sp?) device that must have gone along with the device long ago. I would like to see the tone behaviors and will search out something as you describe.

One issue is that these lenses cover many formats and run from 35mm to 150mm so I was concerned about what it would take to cover that wide of an assortment of things. Now that I'm a bit caught up in this, it might be fun to tabulate and share what I find, at least in terms of resolution when I have so many examples. I have duplicates and in the case of 80mm ƒ4.0 Rodagons, I have 5 examples to compare.

 

[Photo Engineer]

The test charts vary from 35mm to 4x5. If 35mm is used, you can move them from the center to each corner of a larger image to test. I have done this for years.

PE

 

[Bob Carnie]

Craig
I am sure you have thought of this but for apples to apples testing, make sure you are using a glass negative carrier and the test negative is centered in the sweet spot of each lens you are testing.

to find the sweet spot, take out your neg carrier at size of printing and rack your focus down until you can see the condensors*if you are using this sort of enlarger* and make sure the blades of your easel is correctly center within the fall off points you will see. Then position your test negative within this area for repeatability purposes.

 

[rjas]

Do you have a 135mm lens you'd peddle to me?

 

[outwest]

Craig, I found Ctein's method to be very illuminating and easy. This involves the use of a fine graphic dot screen from a graphic arts supply house or a better equipped art store. You just cut a piece to the size of your neg holder and focus the center on your baseboard and then look all around with your focusing magnifier. Not only will you be able to make a judgement of relative resolution and contrast but also of any chromatic aberrations at the edges.