Re: [Leica] Erwin Puts' test for film speed

["Robert G. Stevens" <robsteve@hfx.andara.com>]

Erwin:

I was doing some tests for the proper developing time when I push AGFA RSX
II 100 to an EI of 200.  Agfa states on their web site that to push one DIN
(1/3 stop), increase the developing time by one minute.  For three DIN or
one stop they want it increased by three minutes.  Most E6 films require
only a two minute increase, although for Kodak E100S, they say to rate it
at an EI of 160 when using a one stop push.  This seems to agree with AGFA.
 Since I had not pushed the new RSX II before, I asked the AGFA rep and he
said it should push to 200 with a normal one stop push time.  It seems he
was wrong, or didn't read his own data sheets as my results at rating it at
an EI of 200 and incresing the developer time by two minutes produced
slides darker than I would like.  I used an example for testing for
negative film that you had posted to the LUG and assumed it would work for
positive film.

I did the base level shot with lens cap on, which produced  a black image.
I then shot the metered value of the grey card, using the gray card as a
target.  I took five exposures in all, one at metered and four others one
stop apart each towards successive underexposure (black).  The forth
exposure, which was metered - 3 stops, is still discernable from the base
fog or black image.  I also took a couple pictures using an incident meter
set at ei 200 and they seem fine.  Have I used your method correctly and is
slide film about one stop less able in recording shadow details as compared
to print film?  Should I try rating the film a little slower to get the
fifth exposure discernable from base fog?

Regards,

Robert
 

At 11:36 AM 11/22/98 +0100, Erwin Puts wrote:
>You can not test for accurate film speed by using the greycard and exposing
>it as a mid gray.
>The correct way is this one:
>Take a close-up picture (or as close as you can) from the grey card: expose
>as the meter indicates (reflection from the M or any handheld meter. NOW;
>take a series of pictures everyone one stop more under exposure. Five in
>total. So assume the greycard reading is 1/125 at f/8 take a series with
>A: lens cap attached and
>B: 125/8, and
>C: 125/11 and
>D: 125/16 and
>E: 250/16 and
>F: 500/16 and
>G: 1000/16
>Develop as you wish or have been advised to do.
>The negative exposed with 500/16 should have a very light grey density,
>visibly above fog level (this you see in the negative with lens cap. If
>that is the case your EI value is equivalent to the ISO value. Most often
>you will see that this F neg  is also blank (only fog level). Then you
>should look at the E neg: has this one some density, you should lower your
>EI setting by 1/2 to 1 stop. If you are not interested in deep shadow
>details, just proceed with the higher  setting.
>
>Erwin
>
>
>
>