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View Full Version : Determining shutter relevance to lens.



otzi
15-Oct-2008, 08:00
I would like to know how accurate should the aperture hole size be by measurement using a vernier caliper. On some lenses viewing through either the front or rear cells seems to offer optically different size of aperture and measuring the shutter alone is vastly different (smaller). Which is correct? Should one view through the front or rear cells. And leaving the lens complete or with just one of the cells?

I have found the engravers art to be quite variable in that while some apertures will measure accurately others will not. Which aperture would one pick as the lynch, 16, 22? Is there an industry standard re error? 1/3 stop? More?

All this came about when a lens seller offered a near new Clarion with an old silver dial Copal. Starting at 6.8 ???

I find the black dial small serrations Copal to have at times a quite loose (free) aperture ring. What is the best way to firm this up?

Finally can anyone tell me the meaning of the numbers printed on the aperture scale? Are these lens related and if so how to source this info? [ No not the aperture #ís :D but the very small ones.]

Bob Salomon
15-Oct-2008, 08:06
The small ID number on the aperture scale is the lens manufacturers part number for that aperture scale. Shutter manufacturers do not supply engraved aperture scales. Lens manufacturers do.

ic-racer
15-Oct-2008, 11:07
On some lenses viewing through either the front or rear cells seems to offer optically different size of aperture and measuring the shutter alone is vastly different (smaller). Which is correct?

View through the front cells.

Peter K
15-Oct-2008, 12:10
The aperture scale is an often discussed item also in this forum. Herehttp://www.largeformatphotography.info/forum/showthread.php?t=32332 is described how the f-stop can be measured and also marked on a f-scale. And here http://www.largeformatphotography.info/forum/showthread.php?t=39232 I've described how it can made.

otzi
15-Oct-2008, 18:10
View through the front cells.

ic-racer
Thanks, Is this with or without the rear cells attached?

ic-racer
15-Oct-2008, 18:20
ic-racer
Thanks, Is this with or without the rear cells attached?

The rear element will not affect the pupil size viewed from the front ;)

Peter K
15-Oct-2008, 18:34
There is another method first described by H. Kessler: view through a small hole in the focal-plane through the lens on a glass-ruler laid on the filter-thread of the lens. The viewable part of the ruler correspond to the f-stop.

otzi
15-Oct-2008, 19:19
[QUOTE Bob Salomon form am earlier post]any two 150mm lenses at random are not the same exact focal length. That is why most modern aperture scales have a very small number on them that identify the specific scale.[QUOTE]

Is there any way of determining a connection between this number and the lens. or the number to a scale? It's got to be some where.

If one were to determine a modified aperture measuremnt, where would one get the aperture scale printed/made. Would S.K. Grimes and/or Flutot's do this with out the lens in hand? (I haven't ask them as yet)

Dan Fromm
16-Oct-2008, 05:06
Otzi, Carol directs people who want new aperture scales to SKGrimes.

Depending on the shutter and user requirements, SKGrimes will engrave a new scale on the side of the shutter or on a scale that fits on the shutter's face or cut a prepared scale from a roll of scales (I've seen and touched a couple of such rolls) and attach it.

If you don't want to do it yourself, SKG will do it all for you. But make sure to tell them where you want the scale to be. They recently reshuttered my 58/5.6 Grandagon and engraved a scale on the new old stock shutter's faceplace. In that location, the front cell hides it pretty well. Adam is a very capable and imaginative machinist, but he doesn't always think like a photographer.