Brightness of 8x10" GG image with 210mm G-Claron

[Leigh]

Absolutely not. f/stops are geometric, not photometric.

Then you claim that 100 years of successful photographic technology is rubbish ? ? ?

You'll find your opinion contradicts that of many accomplished photographers.

- Leigh

[Dan Fromm]

The problem is that the 'tolerances and errors' turns to something other than the F8....which essentially answers the question.

Les, I must not have been clear. What matters for uncoated lenses' transmission is the number of air-glass interfaces. This isn't 'tolerances and errors,' its the lens design.

You young folks won't recall this, but while Eugene Lacour, Claude Berthiot's nephew and successor, was Berthiot's chief designer all of the anastigmats they sold were cemented triplets or pairs of cemented triplets, with two and four air-glass interfaces respectively. Towards the end of Lacour's working life, other makers supplemented these type with tessar and celor types, with six and eight air-glass interfaces. Berthiot's 1908 catalog contained a defense of their practice on, among other grounds, higher transmission.

[Leigh]

Berthiot's 1908 catalog contained a defense of their practice on, among other grounds, higher transmission.

I thought we were talking about modern lenses, not 100 year old lenses.

Certainly there is more light loss for each surface pair, but the amount is trivially small. And the aperture scales for a given lens should be corrected for that minor error. They're not "purely" geometric.

You vacillate from one extreme (t/stops) to the other (century-old glass). How about addressing lenses that we currently buy and use.

- Leigh

[Leszek Vogt]

Granted, Dan, I should have included lens design in addition to Leigh's 'tolerances and errors'. OK, throw me under the bus for short-sided lumping.

Ha, the differences between the lenses continue.....for most of us. If you want matching lenses (highly precise), one has to drop anything from 30 to over 100K for a set of primes (Mot pic Schneider, Zeiss, Leica, Cook).

Les

[Dan Fromm]

Granted, Dan, I should have included lens design in addition to Leigh's 'tolerances and errors'. OK, throw me under the bus for short-sided lumping.

Did you mean short sighted? No reason to throw you under a bus for a typo that may have been due to autocorrect. You understand arithmetic, which is what this shining example of thread drift is about.

We're lucky that most of the time our photographs' success is quite resistant to, um, approximations and doesn't require us to understand most of what we do.

[Tim V]

I received a new borosilicate screen from Steve Hopf last week. After installation, I must say that it's a real revelation. Back to what I'm used to with the Linhof screens I've used; very sharp and easy to focus, and much brighter–especially in the corners. Money well spent, in my book. The stock Gibellini screen should go in the bin, but I'll keep it in case of emergency.

[Bob Salomon]

Granted, Dan, I should have included lens design in addition to Leigh's 'tolerances and errors'. OK, throw me under the bus for short-sided lumping.

Ha, the differences between the lenses continue.....for most of us. If you want matching lenses (highly precise), one has to drop anything from 30 to over 100K for a set of primes (Mot pic Schneider, Zeiss, Leica, Cook).

Les

We had supplied matching spec lenses for a small fraction of that from Rodenstock. Usually about a $300.00 surcharge.

[Leszek Vogt]

Bob, I had no idea that Rodenstock was able to do this. However, that would still be a small portion of all those lenses that are out there, as they would continue with F-stop variations.

Recently made T-stop lenses have become v. expensive....well, maybe not Rokinon (cine). Yet, the light transmission of Angenieux 18.5mm T2.5, that was made in the early 1950's will have the same output qualities as recently made Canon 11.5-138mm T2.5, Panatar (Panavision) T 2.5 ....or slew of other optics at this opening. Granted, the image from Ivotar or Panchro Cook (or other glass) may have several other qualities that's desired (sharpness, contrast, coloration, etc), but the light transmission (@T2.5) will remain the same....and that is the beauty of being able to match and intercut scenes in the motion picture. Without going on other tangents, that was all I was trying to say.

Les

[Bob Salomon]

Bob, I had no idea that Rodenstock was able to do this. However, that would still be a small portion of all those lenses that are out there, as they would continue with F-stop variations.

Recently made T-stop lenses have become v. expensive....well, maybe not Rokinon (cine). Yet, the light transmission of Angenieux 18.5mm T2.5, that was made in the early 1950's will have the same output qualities as recently made Canon 11.5-138mm T2.5, Panatar (Panavision) T 2.5 ....or slew of other optics at this opening. Granted, the image from Ivotar or Panchro Cook (or other glass) may have several other qualities that's desired (sharpness, contrast, coloration, etc), but the light transmission (@T2.5) will remain the same....and that is the beauty of being able to match and intercut scenes in the motion picture. Without going on other tangents, that was all I was trying to say.

Les

They, for a charge, will test, match and calibrate lenses.