Another Superachromat 250 ?

[terrestrikon]

Well, I think I want this lens. But I shoot about 98% black and

white, about 20% of that Konica infrared. Developed myself, mainly

in Pyro. For the infrared, instead of zone focussing I figure I

could focus on the subject wide open with some interesting effects.

But for the rest? Would the 250 sa be that much different than using

the 180 (which I've got) with the 1.4x teleconverter (which I

haven't)?.

<br><br>

Kornelius, can you convince me to part with my dineros?

 

Thx,

 

G.

[larry_lambert1]

the real meat of your question will definitely have to wait for the Dr., but for now i could definitely say that 1.4x180 will take a hit in the area of rez, where 250 SA will give you a step up, maybe not a huge step up unless you take some extraordinary techniques into account (video head on video tripod, hands around camera, no larger than f5.6 etc., Dr. Kornelius can refer you to these as well), but a step up nontheless. As i understand it this lens is corrected well into infrared so that optical focus equals infrared focus. I was looking for some funny comment to end this with but it's too late in the evening. anyway, that means that no change in visual focus is necassary, stunning if true!! Makes me wish kodak made IR 120 film, not just a billion feet of perfed 70 mm aerial IR.

[steve_rasmussen]

Well, if correction of four colors were not enough, there are even crystal elements(Fluoite?). This is a special lens that is not only well corrected for longitudinal and lateral color, but is well corrected for the remaining aberrations. There is an obvious concern by Zeiss to reduce spherochromatism in this lens so that marginal zones of the optic did not produce color fringing. The MTF of this lens is incredible. George, do you really need this level of perfection?

[kornelius_j._fleischer]

Yes, George, part with your dineros! Here is why:

 

The Superachromat can give you more resolution! The figures: The Superachromat easily resolves more than 250 linepairs per millimeter on film. The Sonnar 180 will not take you beyond 200, and with the converter, its resolution well be certainly lower.

 

But much more important is this: The Superachromat 250 is the best corrected photo lens on the market. It is the only one corrected so well for chromatic aberrations, that the secondary spectrum is approx. 10 times better corrected compared to usual apochromats. This means for you: In your infrared photography, you can easily and quickly focus in visual light and can rely on getting perfectly sharp images on your infrared negatives. NASA says that the Zeiss Superachromat 250 is the only lens giving them this benefit.

 

The Sonnar 180 cannot deliver this sort of performance. It was not designed with this goal. And with a converter - forget it!

 

Hope this helps.

[terrestrikon]

Thanks very much, Dr. Kornelius.

 

I'll get the lens in August or September. Then I figure it'll take me several years to learn to use it properly! :)

[_____133]

Hi Kornelius

 

Wonderful to have your input. By your statements, do you imply that the 250SA is even better corrected than 350SA?

 

Tschuss.

 

Erik

[cameron_ertman]

George, the reputation of the 250SA is outstanding; however, one reason I went with the 180mm was that it focuses MUCH closer (I don't have my lens notes in front of me but the 180 and the 250SA have a respective repro. of something like 1:6 compared with 1:9, and the 250cfi also focuses closer than the 250SA). I suppose you could put a tube on the SA and still get excellent results. If fairly close focusing capability is not an issue, the SA can't be beat.