Why do some photographers use sensitometry?

[Jorge Gasteazoro]

Clay makes a very good point. The problem is carrying the method to a ridiculous degree. Most of us who use the BTZS become used to it and most of the time forget about the nuts and bolts. If you use the palm pilot the program will tell you to develop for 5.37 minutes. Clearly this is an uneeded accuracy, whenever I have film that has for example development times of 4.45, 5.27, 6.30 I just put all of them in the drum and develop for the average. Film is very forgiving and with a little of magic in the darkroom there is no need to take things too far. Of course, I now have negatives that I rarely have to dodge and burn.

[sanking]

Jorge: "Clay makes a very good point. The problem is carrying the method to a ridiculous degree. Most of us who use the BTZS become used to it and most of the time forget about the nuts and bolts. If you use the palm pilot the program will tell you to develop for 5.37 minutes. Clearly this is an uneeded accuracy, whenever I have film that has for example development times of 4.45, 5.27, 6.30 I just put all of them in the drum and develop for the average. Film is very forgiving and with a little of magic in the darkroom there is no need to take things too far. Of course, I now have negatives that I rarely have to dodge and burn."

This is pretty much the point. People who have mastered BTZS have it stored away in their grey matter and work in the field can be every bit free and intuive as with other systems. For most situations I can calcuate SBR and exposure in about 15 seconds. Then you make the exposure and put a lable on the holder to indicate how it should be developed, and that is that. Great precision is possible but not needed in most cases. About 90% of the negatives I make fall in the SBR 6, 7 or 8 range, and I don't worry about the differnce between 6.4 and 6.0. Regardless of what system you use there is enough latitude in develoment and printing to control small differences in negative average gradient.

[steve simmons]

From Jorge

" ...4.45, 5.27, 6.30 I just put all of them in the drum and develop for the average"

If you are going to BTZS and then average your development what is the point. In a situation like this you are off by 20% on your development time. You are plussing by 1 some of the negs and minussing by 1 others. Are you adjusting the exposure indices for this plussing and minussing?I would never do this. I develop 6-8 negs at a time for their specifc needed development time and I always adjust my ei for plussing and minussing..

Don't you ever give another lecture on why sensitometry is necessary or helpful. This post you made undoes all your claims of precision or the love of craft.

Amazing!!!!!

steve simmons

[Kirk Gittings]

Jorge says,

" development times of 4.45, 5.27, 6.30 I just put all of them in the drum and develop for the average. Film is very forgiving and with a little of magic in the darkroom there is no need to take things too far."

After reading that I feel like a rocket scientist. That amount of generalizing developement times would be unacceptable to me even with my KISS standards. That means you are like 20% off 2/3rds of the time! Where is the precision?

[Jorge Gasteazoro]

C`mon Kirk, I doubt you will see any difference between developing a film for 4 min 30 sec and one for 4 min 45 seconds.......as Clay said, one has to know how far to take the accuracy. Of course, with the BTZS you are free to be as accurate as you want, I doubt you can say that for the KISS methods.

[steve simmons]

"C`mon Kirk, I doubt you will see any difference between developing a film for 4 min 30 sec and one for 4 min 45 seconds"

that is not what you said.

Here is what you said

"example development times of 4.45, 5.27, 6.30 I just put all of them in the drum and develop for the average"

This means that a neg you were told should be developed for 4min 45 seconds would be developed for slightly longer than 5min 30 seconds. This would be about 20% longer than the neg should be developed for. A 20% increase in develoopment can have significant affest on the higher zones and a litle effect on the lower ones. This is enough that most of os would then adjust the ei for that negative,

This is much sloppier than those of us testng w/o a densitometer would ever do. We would know better!!!

steve simmons

[sanking]

Steve Simmons: "This means that a neg you were told should be developed for 4min 45 seconds would be developed for slightly longer than 5min 30 seconds. This would be about 20% longer than the neg should be developed for. A 20% increase in develoopment can have significant affest on the higher zones and a litle effect on the lower ones. This is enough that most of os would then adjust the ei for that negative."

I would have to agree that Jorge's example, which suggsted a range of development between 4:45 and 6:30, is not a very happy one. I just looked at the practical result of developing a number of films in Pyrocat 2:2:100 in rotary at 70F for 4:45 and 6:30, and the median range is an average contrast from .45 at 4:45 to .65 at 6:30. This would be unacceptable to me.

Other developer/film combinations, say weaker solutions, would give less range in average gradient.

[robc]

I wonder how many of you sensitometry nuts try and produce the test prints AA produced. You know, the ones of the patches of hardboard for each zone. Its very informative to do it and doesn't require a densitometer and it will nail your film speed and dev time spot on.

Yes I know AA said you shouldn't calibrate to paper but if paper is not consistent in its range then nailing your calibration to some arbitrary numbers will never be spot on either. i.e. in relation to your prefered papers.

Just try it with a set negs for zone 0 thru zone N (N= how ever many zones you use) and see whether your negs actually fit the paper its supposed to. If not, which I suspect for most people, then tell me what exactly you are all arguing about. On second thoughts don't tell me!

[Kirk Gittings]

Jorge,

I'm sure you were just pulling numbers out of the air for discussion purposes, but yes I can easily be as accurate as that example (at least) with my methods and test it with a simple proper proof every time I make a contact sheet. Don't forget I did the full blown Zone System for years and taught it at university level before backing off to a simpler approach. So I carry all that testing around in the back of my head just as you do.

[John D Gerndt]

Just getting back to the idea that a desitometer is seen by some as a scary thing, it was more scary when they were expensive, for me al least. I felt I had to have a great deal of knowledge to get my money's worth from an expensive instrument. They are plentiful now, I picked one up for less than $100. I'd have to say that it was a cheap AND easy way to bring some solid information to my process.

I have been a pretty good guesser in my day. This is better. You don't have to have a real grip on the science to use a simple tool. Density range is a junior high school concept. Just having a solid number to associate with my results can keep me from drifting off towards what I "think" is about the right paper and printing time.

As I believe knowledge is power, I will continue to struggle to get a lock on consistant negatives. I'll use my desitometer to keep track of my progress. Meanwhile, it is a great tool for saving time and paper.

Cheers all,