Lens & shutter calibration

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John McGraw - 22 Nov 2004 02:40 GMT

Nicholas O. Lindan wrote:

""Kevin" <kkempNOSPAMsprint@earthlink.net> wrote in message

> D76 ... 320 Tri-x (TXP) [sheet film] ... negatives are
> about 2 stops under exposed. [Are Kodak's published
> times reliable?]

Kodak's published development times are the _last_ thing
I would doubt.

If you haven't found the cause it is because it is somewhere
you have not yet looked or that you are sure is not the cause.

Have you tried distilled water, only costs $0.69 to find out?
I found Cleveland city water was the cause of 20 years
of development woes. I only stumbled on to it when I tried
Rodinal and got consistently blank negatives.
One bottle of Distilata and I was hooked; in the succeeding 20
years I have not had _one_ case of mysterious under/non
development. Non-mystery failures are another matter ...

I would doubt _everything_. Does the light meter agree with
a Black-Cat card? Does the shutter jive with a spinning
turntable or the lines on a TV screen - at the speeds you are
using to shoot the Tri-X? Do the aperture settings agree with
a ruler measurement of the entrance pupil? Is the D-76 good?"

Hi Nicholas
Could you refer me to more info about using a spinning turntable or a
TV to check shutter speed, or go into more detail on line? Does one
have to do this w/ film in camera & then process it on can it be done
just by looking through the back of the camera. This is very
interesting

Thanks, John

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Alan - 22 Nov 2004 07:17 GMT

I have seen something about the turntable. Essentially you take a
photograph of an item rotating on the turntable and can determine the
shutter speed by the degrees through which an object has moved (you
need to work out the time for one revolution at the speed you set the
turntable first). If it takes 1.33 seconds (45rpm) for one
revolution, shutter speed equals degrees of rotation in image divided
by 360 and multiplied by 1.33. If the object completed 75% rotation
in the image, 270 divided by 360 times 1.33 equals 1 second.

Another way is to try the and fashion the item here:
http://www.geocities.com/Yosemite/2131/shspeed.html
I tried it and was able to successfully get it to work (though not
immediately). I just made a rough version and tested a shutter set at
1/30 sec. Result from Cool Edit Pro was 0.034 seconds. Close enough
for me!

Regards,
Alan

>Nicholas O. Lindan wrote:
>
[quoted text clipped - 32 lines]
>
>Thanks, John

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John McGraw - 22 Nov 2004 20:07 GMT

> I have seen something about the turntable. Essentially you take a
> photograph of an item rotating on the turntable and can determine the
[quoted text clipped - 14 lines]
> Regards,
> Alan

Thanks, Alan. That's great, John

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John McGraw - 22 Nov 2004 20:21 GMT

> I have seen something about the turntable. Essentially you take a
> photograph of an item rotating on the turntable and can determine the
[quoted text clipped - 14 lines]
> Regards,
> Alan

Hi Alan

Woops, I just had a premature post message.
I was going to say that I feel like a kid @ XMAS w/ a new toy. Running
all around the place grabing cameras, & testing w/ the TV. Next I'll
have to make a few rounds of pawn shops looking for a good & cheap
turntabe. I've been wanting an excuse to buy a good old turntable.

Thank you, John

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PATRICK GAINER - 24 Nov 2004 04:47 GMT

>
>
[quoted text clipped - 29 lines]
>Thank you, John
>

These methods work. However, some of the developing times for the new
Tri-X are wrong as they appear on the carton for HC-110. IIRC, the times
given for 1+31 dilution were those for 1+15, which are much too short.
Check that out as you check your shutter speeds.

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David Nebenzahl - 22 Nov 2004 07:25 GMT

On 11/21/2004 6:40 PM John McGraw spake thus:

> Nicholas O. Lindan wrote:
>
[quoted text clipped - 12 lines]
> just by looking through the back of the camera. This is very
> interesting

Regarding the TV testing method (the simpler of the two), this technique only
works on the speeds above 1/60th. It is done by looking through the film gate
as the shutter is fired and observing the pattern caused by the shutter
catching part of the screen-blanking interval.

This method is pretty clearly described on one of Rick Oleson's indispensible
camera-stuff pages: http://rick_oleson.tripod.com/index-135.html.

Signature

Don't blame Ralph Nader: blame Gavin Newsom.

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Jim Phelps - 22 Nov 2004 16:52 GMT

> Regarding the TV testing method (the simpler of the two), this technique
> only
[quoted text clipped - 5 lines]
> indispensible camera-stuff pages:
> http://rick_oleson.tripod.com/index-135.html.

Remember, this will only work in areas where the power is 60 Hertz (and
there for the Vertical refresh rate of your TV). If you live in 50 Hertz
land, then you'll have difficulty assessing your results properly (or your
shutter is off:~).

Your PC screen may be capable of providing a 60 refresh rate regardless of
where you live. Might also work with other (higher) refresh rates, but I'm
not sure they'll coincide with the shutter speed logarithmic steps (for
instance, mine will do 60 Hz and 120 Hz, but not 125 Hz).

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John McGraw - 22 Nov 2004 19:54 GMT

> On 11/21/2004 6:40 PM John McGraw spake thus:
>
[quoted text clipped - 22 lines]
> This method is pretty clearly described on one of Rick Oleson's indispensible
> camera-stuff pages: http://rick_oleson.tripod.com/index-135.html.

David, that's really cool, & so is Oleson's site. I saved it.

I wish I had thought about this more & figured it out on my own. I
some what had the turntable figured out. It could be used for <1/60
sec.

Thank you, John

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