[rollei_list] Re: 500/5.6 Tele Tessar for SL66 Comments

  • From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
  • To: <rollei_list@xxxxxxxxxxxxx>
  • Date: Fri, 5 Jan 2007 16:11:55 -0800


----- Original Message ----- From: "Ellestad" <ellestad@xxxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Friday, January 05, 2007 1:56 PM
Subject: [rollei_list] Re: 500/5.6 Tele Tessar for SL66 Comments


Hi Mike -

----- Original Message ----- From: "Mike Kovacs" <mskovacs@xxxxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Friday, January 05, 2007 6:04 AM
Subject: [rollei_list] Re: 500/5.6 Tele Tessar for SL66 Comments


Thanks a bunch Tim - that was really helpful, as was the sample photo that you sent privately. Do you mind if I put that sample image up in
the RUG Flickr gallery so interested readers can see it?

We'd better not post it. It is currently in use on an exclusive usership
contract with the firm that I shot it for.

Your mention of tripod goes without saying to me. There are a lot of 500/8 Hassy shooters I have read about that say the lens is so-so. This made me immediately wonder what kind of support and long lens technique they are using. No doubt the new APO lenses are probably better yet
though.  Too bad that the SL66 misses the boat here.

Yes the new APO long lenses are probably slightly better. I know from years of cine shooting, though, that when the lastest APO long lenses came available in cine mounts the image improvements weren't nearly as significant as we expected. Coating improvements were more notable. Is there an APO 500 that will cover 6x6? (Vignetting is an issue that often gets little discussion - it is a real image quality killer IMO. The 500 f5.6
doesn't show any significant vignetting even at 5.6.)

One question - the 500/5.6 is focused by the bellows on the camera,
correct?

Yes, focus is still the camera bellows.

PS I have to assume the Hassy 500/8 is the same lens, just constricted
to f/8 by the leaf shutter?

No, I think that is a different design yielding a more compact lens. The front element of the Rollei 500 uses every bit of a 96mm filter. Hasselblad
did have an APO f8 later.

You know, I wouldn't be surprised if fewer than 100 of these lenses were
ever made.
---
Rollei List

I wonder if the lens is truly apochromatic. A lot of current lenses with the name prefix APO are just well corrected achromats. A true apochromatic lens is corrected for longitudinal chromatic aberration for three colors and spherical aberration for two colors. In addition, most are corrected for lateral chromatic aberration. The published data for the current crop of "APO" lenses often includes a graph of longitudinal chromatic deviation, i.e., the change in focus for color. These cross the zero line twice, an apochromat will cross the center line three times. Note that the overall chromatic deviation of an apochromat is not necessarily better than an achromat. The apochromat may be correct for three colors but still have greater deviation outside of these colors. This is probably rare in a commercial true apochromat but still quite possible. An apochromat is not necessarily a better performing lens than a acromat. The overall performance depends on many other factors beside longitudinal color correction. I will add that many telephoto lenses, especially some of the early ones had severe color fringing. This may have been due to poor longitudinal chromatic correction but the extreme asymmetry of such lenses can lead to large amounts of lateral chromatic. This aberration is one where the _focus_ of the colors is not too different but the _size_ of the image varies. A completely symmetrical lens operating at equal image and object distances (completely symmetrical optical path) is inherently free of lateral color, however, symmetrical lenses, even for objects at infinity, have substantial cancellation of lateral color. Non-symmetrical lenses, like the Tessar or any telephoto or retrofocus lens, must be corrected for lateral color in other ways than relying on symmetry or partial symmetry.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx






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