Hello all!

Thank you all for welcoming a new comer to your forums. It was very nice to have a question answered without digs, insults and hostilities. The answers were great!

Have another for you guru's.

A little background.

I just recently purchase an old Macbeth TD-502 densitometer. The seller said that it wasnt able to calibrate but it returned consistent results. The price was right and I thought that I could take readings from a "known" Stouffer T3110 step wedge, use that as a base and read negative densities.

When I got the machine, I decided to see if I could calibrate it, despite the seller's oppinion. Low and behold, it calibrates! Every step reading of the T3110 is what it's supposed to be. Wow, got a break!

Now, off to the races. Let's take some gray card exposures, FB+F, Zone I, Zone V and Zone VIII at varying speeds. 28, TMAX 100 35mm, exposures in all; Whoops can't find either one of my gray cards, use a piece black construction paper instead. (This should be cool right? Its all about what the equipment 'thinks' it's looking at)

Equipment/Chemicals/Process:
Canon F1 original w/ 50mm f/1.4 lens
Pentax 1/21 analog spot meter
TMAX 100 35mm bulk
D-76 1:1 developer
Temp/Time: 68/8.5 min

develop as per my normal development procedures which is the Kodak recommendations for TMAX 100 and D-76 1:1. Agitation is consistent at 5 inversions every minute.

After letting the film dry over night I get everything together to read the densities. I am as giddy as a kid in a candy store! Make sure the densitometer is calibrated, yup step 1 reads .05; step 31 reads 3.05, steps in the middle are what you'd expect. Great!!!

Lets read the FB+F and Zone I exposures from the 100 speed test to gauge the film speed.

FB+F = .21
Zone I = .22

Huh? thats odd, I can see the density in the neg for Zone I, but I am shooting for .1 + (FB+F) right? Well I should see something close to .31, right?

On to the next group of exposures (125) these are the same. ??? Lets just clear to the end for the 50 ASA test. It reads

FB+F .21
Zone I .23

What is going on here? only .02 over FB+F? Am I missing something?

What are your opinions about whats wrong? I have my own opinions, but I will keep them to myself for now. Don't want to boot strap idea's about whats wrong.

Thanks again for all your help.

Best regards,

Rick