View Full Version : Difference between ED glass and non-ED glass

chris jordan
30-Aug-2004, 16:58
Hi guys, I have a technical lens question; please only respond if you have specific information that is right on point.

I am trying to buy the sharpest lens possible, for shooting 8x10 Astia 100F to be drum-scanned and printed very large (60" wide). Every other part of my process (film, camera, scanner and printer) are the highest quality possible, so currently the limitation on the sharpness and detail of my prints is the quality of my lens. My prints are large enough that even the slightest improvement in my film's sharpness would help with print quality.

I'm now using a Nikkor 450M and a Fujinon 300A f/9, which give me good results except near the edges of the image circle (the Fuji shows some color fringing and the Nikkor gets pretty fuzzy out near the edges). But I suspect that the best lens available might be better even at the center-- especially if it is made with ED glass.

So I have been researching lenses with the idea of replacing both of my lenses with the best glass available, and it looks like the Rodenstock Sironar-S series (made with ED glass) is the best lens that money can buy. The question is, how much actual difference will there be between the sharpness of images made with this lens compared to my other lenses?

Any thoughts by those with some expertise on this topic?



30-Aug-2004, 23:21
Why not try out the f10 process Nikkors. Perhaps put one in a shutter. I have a 260mm that has to be the sharpest lens I've ever seen. Unbelievable corner to corner sharpness even wide open. I've never seen a lens this good in the corners before. Covers 11x14/7x17.

Michael S. Briggs
31-Aug-2004, 00:15
I can't say how big the change will be from the lenses you mention because I haven't done that exact comparison. Probably few if any participants in this forum have because the longer focal lengths Apo-Sironar-S lenses are uncommon. I did some tests of the baby brother of the Nikkor-M that you have, and was surprised to find that my judgement of the coverage was somewhat less than Nikon's, depending on the magnification at which the negative was examined: http://largeformatphotography.info/lfforum/topic/494534.html (http://largeformatphotography.info/lfforum/topic/494534.html#373881). The plasmat design of the Apo-Sironar-S will definitely give more coverage than a Tessar, so if the fuzziness that you see near the edge is at the limits of Nikon's rated coverage, I think you will see a definite improvement at the edges by using any modern plasmat type lens. The extra elements of the plasmat design give the lens designer more degrees-of-freedom to work with. I don't know how much improvement you will see at the center.

There are several theoretical reasons to expect better performance. The purpose of ED glass is to reduce chromatic abberation, so if you are seeing color fringing, there should be some improvement. The Fuji-A appears to be symmetric and is probably designed for 1:1 (http://largeformatphotography.info/lfforum/topic/498397.html), so if your subjects are significantly larger than 8x10, switching to a lens designed for studio to distant objects, such as the Apo-Sironar-S, should bring some improvements.

From a graph that Nikon published for a 35 mm Nikkor, I have suspicions that the ED glass of Nikon isn't merely Extra-Low Dispersion glass, but is Extra-Low Dispersion with Anomolous Partial Dispersion. Use of this type of glass gives the lens designer a way to reduce the secondary spectrum of chromatic abberation. Unless someone knows of a patent on one of these modern lenses, it is hard to know exactly what is being done.

31-Aug-2004, 03:54
if weigth is important, and you don't use movements, you should try an apo ronar MC on copal, otherwise i will go for an apo sironar S or maybe an apo symmar L ! If you don't need the full coverage of these lenses, then maybe an apo symmar will be as good !

31-Aug-2004, 04:04
if weigth is important, and you don't use movements, you should try an apo ronar MC on copal, otherwise i will go for an apo sironar S or maybe an apo symmar L ! If you don't need the full coverage of these lenses, then maybe an apo symmar will be as good !

Schneider have discontinued the Apo Symmar range of lenses, and a replacing selected models with redesigned Apo Symmar L lenses that have larger image circles (more movement) and new barrels that have a rear filter mount thread that is the same as the front filter thread. 100 / 135 / 240 / 360mm versions have been discontinued, and the 480mm totally redesigned

Apo Symmar L 480/f8.4 L / Copal 3 / ic 500mm / filter 105mm (1,580 + tax robert white) Apo Symmar L 300/f5.6 L / Copal 3 / ic 430mm / 105mm / (1,130 + tax robert white)

it looks like, the longuest sironar S is 360/f6.8 / Copal 3 (1,884 + tax robert white)

Nathaniel Paust
31-Aug-2004, 11:30
The term ED glass really just says that the dispersion of the glass is "extra-low". Basically, it refracts blue end of the spectrum and the red end of the spectrum at pretty close to the same angle. Unfortunately, I haven't found an exact spec to call glass ED, it seems like it's at least partially just a marketing term. Terms like SLD for "special low dispersion" definitely seem to just be marketing claims.

So a well designed lens with ED glass should allow you to get rid of the color fringing you're getting from the Fuji lens. Whether it would give you any better sharpness than the Nikon is hard to say, it would really depend on whether the unsharpness was coming from a color effect.

Now to things that I can't prove. Assuming you're shooting at a normal f-stop, maybe f16 or f22, I'm guessing that switching lenses won't do much to improve center sharpness. Diffraction starts to be the significant limit on resolution at relatively wide f-stops.

Brian Ellis
31-Aug-2004, 15:13
I sold my 135mm Nikon W lens to buy a 135mm Sironar S lens after reading raves about the Sironar at various places. I see no difference at all in the technichal quality of the photographs made with it as opposed to those made with the Nikon or with my other lenses. In my opinion modern lenses of the same design from the four major manufactures are all so good that differences among them are almost non-detectable except with careful side-by-side comparison, viewing with a loupe, etc. However, I only photograph black and white, maybe differences among my lenses would be more obvious if I photographed with color or if I really pored over the negatives and prints to seek out the differences.