I'm looking for some help from people with more expertise in this area than myself!

I have read with interest the recent thread about the relative merits of the APO lenses offered by Rodenstock and Schneider, and have followed up the links referring to technical data. I have to admit to being bemused by it, and unable to use the data to make an informed choice.

My intention had been to go for the Rodenstock 105mm lens, rather than the Schneider 90mm. I'm sure both are superb lenses, which will give great results. I know there is some difference of opinion about the length of lens needed to print optimally from 6x7 format negs, but there seems to be some indication that 105 might be marginally better than 90 for this format. In any event, it can't hurt, as the images will be slightly closer to the "sweet spot" of the lens.

Although I remain to be convinced that this difference matters, I had deciced to go for the Rodenstock on the basis that both are great lenses, but the extra focal length might help.

However, putting the focal length issue to one side for a moment, some people seem to be arguing that the Schneider is slightly better optically into the corners than the Rodenstock (though this conclusion was based on a shorter Rodenstock lens than the ones I'm considering). I have looked at the technical data referred to, but can't make sense of it to draw a conclusion. Can anyone help me?

-- Ed Hurst (BullMoo@hotmail.com), August 01, 2001

Answers

I should have said that I am getting the Schneider data from http://www.schneideroptics.com/enlarge/datasheets/pdf/apocpn4,5- 90.pdf and the Rodenstock data from http://www.butzi.net/rodenstock/apo-rodagon/105mm.htm.

All help would be much appreciated!

-- Ed Hurst (BullMoo@hotmail.com), August 01, 2001.

Ed, after reviewing the data for APO and standard lenses, it looks like if you are exposing at f/11, the non-APO lenses are just as good (maybe better?) for all practical purposes (except perhaps color correction).

Another factor to consider is the optimum magnification level. The Rodenstocks are optimized for a 6x magnification (can't find info on the Schneiders). Using a 105mm lens for 6x7 will increase the magnification level by about 1.17 (105/90). If you usually do 11x14's or smaller, the 105mm will get you closer to the optimum magnification level than a 90mm (14/2.75*1.17=5.96). However, if you frequently print at 16x20 and above, the 90 mm will get you closer to the optimum (6x) magnification level (not to mention the issue of enlarger height).

-- Michael Feldman (mfeldman@qwest.net), August 01, 2001.

Unless you're using a glass negative carrier, and have your enlarger perfectly aligned, you probably won't see slight differences in lens quality.

As another poster mentioned, working at optimum magnification is also important. For different size prints, I use 80mm, 105mm, and 150mm for 6x7.

-- Chris Ellinger (chris@ellingerphoto.com), August 01, 2001.

Many thanks for your views so far! As ever, there seem to be many variables at play. I intend to use a glass carrier, and check alignment carefully. I must admit that 10x8 and 12x10 are my most common sizes of print, but I do do occasional larger prints (occasional but important!).

I understand your points about optimum magnification, but does your analysis of the data suggest any issues about which lens might be better in terms of optical quality (including into the corners)?

Thanks again!

-- Ed Hurst (BullMoo@hotmail.com), August 01, 2001.

If this lens is for B&W printing only, then paying extra for an Apochromatically corrected lens is a complete waste of money, IMHO.
VC printing paper is only sensitive to blue and green light, so both theoretically and practically, it makes absolutely no difference whether the red and yellow are brought to the same focus.

I've used Schneider enlarging lenses a great deal, and I've yet to see a bad one. I believe that it would be difficult to improve on the B&W print quality that can be got from the Componon-s series of lenses. Maybe an MTF machine could detect some slight improvement with a more expensive lens, but I sincerely doubt that any unaided human eye could see such a difference.
This shouldn't be taken as a criticism of Rodenstock lenses. I'm sure they're equally as good. I've used Rodenstocks in some of the darkrooms I've worked in, but I've never been moved to spend my own money on one.

-- Pete Andrews (p.l.andrews@bham.ac.uk), August 01, 2001.

For your situation, I think that the most important variables are the f/stop you normally use for printing, and the print size. I like to use f/11 (or half stop between f/8 and f/11) to ensure good DOF. This enables me to use a glassless negative carrier and solves a multitude of sins with regard to perfect enlarger alignment.

At f/11, I think the non-APO's may in fact be better (and a lot cheaper). I am assuming you do primarily B&W work, but even if the APO's had some advantages in terms of color correction, I doubt you would notice at f/11. There is some theoretical advantage to using f/5.6 rather than f/11 to reduce diffraction effects, but this is probably splitting hairs. Unless you have some light output problems with your enlarger that requires you to use f/5.6, I can’t see the justification for the APO’s on B&W work.

In comparing the Rodenstock 105mm APO and the Schneider 90mm APO, I would say that for your print sizes, the Rodenstock would be better because of the optimum magnification factor. Also, the 105mm uses less of the very edge of the lens compared to the 90mm, which is where the worst performance is (for almost all performance criteria). OTOH, Schneider has a very slighter better reputation than Rodenstock (based upon e-Bay resale prices), but this may not be based on actual performance.

A good compromise is the Schneider 100mm f/5.6 (non-APO). The actual focal length is 102.3mm. But the Rodenstock, El_Nikkor, and Fujinon (at Badger Graphics) 105mm non-APO’s are also excellent lenses.

-- Michael Feldman (mfeldman@qwest.net), August 01, 2001.

One nice thing about these comparisons is that you can't really make a "mistake". All the top lenses by the top makers are very good. I just wanted to point out that "APO" has become a marketing term only. It has no specific technical meaning regarding construction or correction.

-- Conrad Hoffman (choffman@rpa.net), August 01, 2001.

I think it's fair to say APO lenses have better color correction than the non-APO lenses by the same manufacturer. But you are correct in saying that there is no internationally accepted measurement standard regarding APO correction numbers. I personally don't think this is a big problem, especially since Rodenstock and Schneider publish performance graphs, but of course others may disagree.

-- Michael Feldman (mfeldman@qwest.net), August 01, 2001.

A while ago, I was talking to one of the lens manufacturers about APO lenses being used for black & white, asking whether or not the colour correction really yields any significant benefit. They were adamant that it would. I suppose they would say that, of course! Any views?

-- Ed Hurst (BullMoo@hotmail.com), August 01, 2001.

I guess there's also the fact that the APO lens is a faster lens, making it easier to focus critically...

-- Ed Hurst (BullMoo@hotmail.com), August 01, 2001.

Unless you were in Germany speaking German, you were probably talking to one of the MARKETING companies that import the lenses into the US.

-- Michael Feldman (mfeldman@qwest.net), August 01, 2001.

It was actually in the UK, and he was described as a "technical expert". Not sure I'm taken in by this - interested in hearing views on the matter...

-- Ed Hurst (BullMoo@hotmail.com), August 01, 2001.

The APO lenses do perform better at f/5.6 than non-APO lenses, even for B&W. But as previously stated, I prefer to stop down for greater DOF.

-- Michael Feldman (mfeldman@qwest.net), August 01, 2001.

So at f8 or f11, no discernible difference...?

-- Ed Hurst (BullMoo@hotmail.com), August 01, 2001.

I am not an optics expert. However, in looking at the performance graphs referenced in one of the posts above, the non-APO lens is actually better at f/11 than the APO lens for most criteria except color correction (which is not applicable for B&W). Obviously this is because the APO lens is optimized for f/5.6. If I am reading this incorrectly, someone please let me know. At f/8 it is difficult to be certain because not all the charts show f/8 performance.

-- Michael Feldman (mfeldman@qwest.net), August 01, 2001.

Lens performance graphs are only 'typical' at best. Individual sample variation is probably greater than the difference between a so-called Apo, and a standard lens. Use your own eyes, for goodness sake.
Does a print from a top-of-the-range non Apo lens have excellent definition? If the answer is yes, and, to my mind, it is; then what's the point of trying to improve on it?
Another simple little test: Can you see any trace of colour fringing through a grain magnifier with a non Apo lens? I certainly can't.
Does the grain appear to change hue as focus is shifted? Again, I can't see it. Colour fringing is a dead-giveaway of an aberration called 'lateral colour', and is easily seen in a lot of taking lenses. It usually goes hand-in-hand with straightforward chromatic aberration, and its complete absense is usually an indication that the colour correction of the lens is very good.

The above visual evidence, taken together with the narrow colour sensitivity of B&W printing paper, is enough to convince me that buying Apo enlarging lenses would be a complete waste of my money. But, hey, it's not my money that we're talking about spending here.

-- Pete Andrews (p.l.andrews@bham.ac.uk), August 02, 2001.

I strongly recommend Ctein's book "post Exposure". He has extensive sections on enlarging lens selection. And yes, if everything else is optimum then the quality of the enlarging lens does matter, especially if you are doing variable contrast B&W.

-- pat Raymore (patrick.f.raymore@kp.org), August 07, 2001.

Before spending money on expensive lens upgrade, be absolutely sure that your enlarger is perfectly aligned and working as well as can be . Unless this proviso is satisfied, the best enlarging lens in the world will still give you unsatisfactory prints.

-- Samuel Tang (samueltang@austarmetro.com.au), August 17, 2001.

Ed, I don't have information on the specific lenses you have in question, but I can offer some personal insight, and some direct from Schneider.

At the NYC Photo Expo last year I met the VP in charge of the Componon line. I was, at the time, comparing the Rodenstock APO 50mm and the Schneider Componon-S. The VP I spoke to told me that the Componon lens line should (or could) actually be considered as APO lenses--they were that well corrected. Nevertheless, I, being a true NYC skeptic, dismissed his assertion and bought a Rodenstock APO. The allure of an APO lens was too strong to resist.

I'd like the story to end happily there, but the fact is, I was never happy with the Rodenstock APO lens. I tried endless alignment tricks, glass carriers, and so on. The lens had very good contrast, but it simply wasn't that sharp. I subsequently rented a series of enlarging lenses from Ken Hansen Photo till I had exhaused nearly every option, and finally wound up purchasing a 50mm Componon-S! I might also note that I tried two Nikkors: one, a new one, and one old one (knurled barrel). Of those two, the new one was quite sharp but had miserable contrast. The old one was the sharpest lens of all those I tested, with very good contrast. I actually bought it as well since it was cosmetically beat-up and therefore quite cheap. Optically, believe it or not, it's a toss between the Componon and the old Nikkor. I do use the Componon more often because I like its aperture lever. In summation, I think the Nikkor lens I have is a freak, while the Componon is pretty much representative of the line. One thing for sure, I will never buy another expensive Rodenstock APO.

-- Ted Kaufman (writercrmp@aol.com), August 17, 2001.

Many thanks to you all for your views and advice - very valuable. I've got some thinking to do! I think it's going to be a Schneider Componon-S...

Ed

-- Ed Hurst (BullMoo@hotmail.com), August 21, 2001.