neil poulsen
4-Nov-2001, 21:21
After my last post on this topic, I needed to determine whether or not I was exp eriencing batch to batch variability for ID11. My last data were confounded wit h the effects of doing calibrations at the same time, so I really only had a sus pician. Before going to the trouble of getting a scale, chemicals, etc. for mix ing my own chemistry, I decided to test specifically for batch to batch variabil ity.
I used three different batches of ID11 chemistry. SMALL: Chemistry for 1 Liter purchased at Pro Photo. OLD: Chem for 1 Gallon purchased about 1.5 to 2 years a go. NEW: Chem for 1 Gallon purchased two weeks ago at Citizens Photo. I debate d about using old chemistry, but Ilford technical support said there was no diff erence and that ID11 should last indefinately. So, it was included.
I exposed 9 sheets of film (all from same box) to Zone 8 level of light. Apertu re left untouched, and shutter was "exercised" prior to exposures. Exposed at f 8 for 1/8th second assuming ASA of 400. Recent testing of lens shows this speed to be in the interval (126 thousandths, 129 thousandths). Separately tray deve loped each sheet of film in small glass Pyrex tray for 11 minutes 7 seconds at 7 2 deg using Zone VI compensating developing timer. Chemistry mixed fresh 1:1 fo r each sheet of film.
DATA: Small: 0.805, 1.010, 1.045. New: 0.90, 1.00, 1.22. Old: 0.905, 1.025, 1.19.
CONCLUSIONS: No differences found between batches of film chemistry. Average d ensities (and standard deviation) of three sheets of film for each batch are SMA LL: 0.9533 (S.D. 0.1296), OLD: 1.0400 (S.D. 0.1431), NEW: 1.0400 (S.D. 0.1637). Pooled standard deviation is 0.1432, which is too high. (P-Value on one-way an ova was 0.717.)
SUMMARY: I was very surprised, given the high variability, that OLD and NEW ave rages were arithmetically equivalent! This was not a mistake. Likely sources o f variability I'm experiencing are shutter (will retest), tray development (prob ably!), perhaps film (I doubt it), meter (will have checked), or mixing (unlikel y). Based on my results, I would not have a problem at this time using differen t batches of ID11 film developer.
NEXT STEPS: I need to improve this variability. It's too high, as much as an e ntire zone. It may be tray development, but I was extremely careful to be as co nsistent as possible. I hate to think that my 8x10 negatives could be subject t o this kind of variability. Looks like I have a winter project. I may try this test again, after I improve variability.
TECHNICAL DETAILS:
1] My meter read dead-on before and after every exposure. My light source is on a track mounted on a tripod, so I can make very small adjustments. If the line on my Pentax Spotmeter V didn't line up EXACTLY to an EV of 10, I adjusted the light source. See previous post for other details on test pattern.
2] Developed each sheet in 20 English fluid ounces, so there was plenty of devel oper. About 3/4 inch in small tray, so film was always submerged. Chemistry wa s separately mixed for each development. Average temperature was kept within 1/ 4 degree, usually less. (Actual temperature within 0.4 degrees, usually much l ess.) I have an electronic thermometer accurate to tenths. I measured the deve loper temperature before and after, averaged these values, and compared to targe t temperature of 72 deg. Used a Zone VI compensating developer timer, so any di fference in temperature from target was compensated. Any effect due to temperat ure was negligible with this device, since previous testing concluded that if I' m within one degree, compensated development time will be accurate to within 3 s econds. Agitation was as exact as I could make it. Lifted each side of tray 5 times at start and twice every 30 seconds. Lifted each side about the same heig ht. All developers "seasoned" for at least 24 hours after mixing.
3] Measured densities using old MacBeth Quantilog densitometer. Stouffer's test strip w/31 steps shows this device accurate to within 0.015 D. Checked calibra tion before and after each measurement.
I used three different batches of ID11 chemistry. SMALL: Chemistry for 1 Liter purchased at Pro Photo. OLD: Chem for 1 Gallon purchased about 1.5 to 2 years a go. NEW: Chem for 1 Gallon purchased two weeks ago at Citizens Photo. I debate d about using old chemistry, but Ilford technical support said there was no diff erence and that ID11 should last indefinately. So, it was included.
I exposed 9 sheets of film (all from same box) to Zone 8 level of light. Apertu re left untouched, and shutter was "exercised" prior to exposures. Exposed at f 8 for 1/8th second assuming ASA of 400. Recent testing of lens shows this speed to be in the interval (126 thousandths, 129 thousandths). Separately tray deve loped each sheet of film in small glass Pyrex tray for 11 minutes 7 seconds at 7 2 deg using Zone VI compensating developing timer. Chemistry mixed fresh 1:1 fo r each sheet of film.
DATA: Small: 0.805, 1.010, 1.045. New: 0.90, 1.00, 1.22. Old: 0.905, 1.025, 1.19.
CONCLUSIONS: No differences found between batches of film chemistry. Average d ensities (and standard deviation) of three sheets of film for each batch are SMA LL: 0.9533 (S.D. 0.1296), OLD: 1.0400 (S.D. 0.1431), NEW: 1.0400 (S.D. 0.1637). Pooled standard deviation is 0.1432, which is too high. (P-Value on one-way an ova was 0.717.)
SUMMARY: I was very surprised, given the high variability, that OLD and NEW ave rages were arithmetically equivalent! This was not a mistake. Likely sources o f variability I'm experiencing are shutter (will retest), tray development (prob ably!), perhaps film (I doubt it), meter (will have checked), or mixing (unlikel y). Based on my results, I would not have a problem at this time using differen t batches of ID11 film developer.
NEXT STEPS: I need to improve this variability. It's too high, as much as an e ntire zone. It may be tray development, but I was extremely careful to be as co nsistent as possible. I hate to think that my 8x10 negatives could be subject t o this kind of variability. Looks like I have a winter project. I may try this test again, after I improve variability.
TECHNICAL DETAILS:
1] My meter read dead-on before and after every exposure. My light source is on a track mounted on a tripod, so I can make very small adjustments. If the line on my Pentax Spotmeter V didn't line up EXACTLY to an EV of 10, I adjusted the light source. See previous post for other details on test pattern.
2] Developed each sheet in 20 English fluid ounces, so there was plenty of devel oper. About 3/4 inch in small tray, so film was always submerged. Chemistry wa s separately mixed for each development. Average temperature was kept within 1/ 4 degree, usually less. (Actual temperature within 0.4 degrees, usually much l ess.) I have an electronic thermometer accurate to tenths. I measured the deve loper temperature before and after, averaged these values, and compared to targe t temperature of 72 deg. Used a Zone VI compensating developer timer, so any di fference in temperature from target was compensated. Any effect due to temperat ure was negligible with this device, since previous testing concluded that if I' m within one degree, compensated development time will be accurate to within 3 s econds. Agitation was as exact as I could make it. Lifted each side of tray 5 times at start and twice every 30 seconds. Lifted each side about the same heig ht. All developers "seasoned" for at least 24 hours after mixing.
3] Measured densities using old MacBeth Quantilog densitometer. Stouffer's test strip w/31 steps shows this device accurate to within 0.015 D. Checked calibra tion before and after each measurement.