Sensitometer for BTZS testing

donbga · Mar 17, 2007

Hi Folks,

I'm curious to know if anyone is using a sensitometer for BTZS film testing?

Thsese units seem to appear on eBay frequently but most are designed for xray film testing. Would those be acceptable for general purpose BTZS film testing?

Thanks,

magic823 · Mar 17, 2007

You need a EG&G Mark V Sensitometer, not the X-Rite models that pop up on ebay. The EG&G models do popup ocassionally, I got mine there. There are several us us here that have them. I know Sandy King and I both do.

Steve

donbga · Mar 17, 2007

magic823 said:
You need a EG&G Mark V Sensitometer, not the X-Rite models that pop up on ebay. The EG&G models do popup ocassionally, I got mine there. There are several us us here that have them. I know Sandy King and I both do.

Steve

Thanks. I knew that Sandy used an EG&G and that Don Hutton uses one but I thought I might ask and see what others are using.

sanking · Mar 18, 2007

donbga said:
Thanks. I knew that Sandy used an EG&G and that Don Hutton uses one but I thought I might ask and see what others are using.

Don,

The best one out there, IMO, is the EG&G Mark VII. I think Steve has the same unit, and it is the "standard" in Troop and Anchell"s book on film developing. The EG&G is the *only* sensitometer you can expect to find on the ebay market that was designed for testing of continuous tone panchhromatic film. You can find other sensitometers, Wejex for example, that were designed for other purposes, but none are as versatile as the EG&G Mark VII for testing panchromtic film.

Sandy

donbga · Mar 18, 2007

sanking said:
Don,

The best one out there, IMO, is the EG&G Mark VII. I think Steve has the same unit, and it is the "standard" in Troop and Anchell"s book on film developing. The EG&G is the *only* sensitometer you can expect to find on the ebay market that was designed for testing of continuous tone panchhromatic film. You can find other sensitometers, Wejex for example, that were designed for other purposes, but none are as versatile as the EG&G Mark VII for testing panchromtic film.

Sandy

Sandy,

Thanks for reminding me of the Troop and Anchell reference, I had forgotten all about it.

I suppose I'll keep watching for an EG&G. Don has kindly offered to let me borrow his to test with.

ic-racer · Mar 31, 2007

EG&G vs WEJEX

magic823 said:
You need a EG&G Mark V Sensitometer, not the X-Rite models that pop up on ebay. The EG&G models do popup ocassionally, I got mine there. There are several us us here that have them. I know Sandy King and I both do.

Steve

I really like my Wejex but I just picked up an EG&G Mark VI and am waiting for shippment.

I have had the Wejex apart to clean and restore it and I like the fact that there is no power supply (all AC) and it can easily be repaired and I am sure will last my lifetime.

In terms of the EG&G, I understand it uses a xenon flash circut, is that correct? Any resources for schematics or shop manuals for these units? The one I am getting supposedly is in proper working order, but if I am to rely on the device for any testing, I need to ensure that I can keep it running.

I know from experience that just trying to source a replacement capacitor for a Rollei E36RE Flash is impossible (mostly because the dimensions of the flash housing). I suspect that because the EG&G Mark IV has a bigger housing, aftermarket parts replacement options are better than a camera photoflash.

Although it was mentioned that the EG&G is the only one really designed for continuous tone b&w film, the Wejex I have does have a 'white' light source. Basically it is a white bulb and I have an 80A filter in the filter slot.

I'd like to get both densitometers together and do a side by side comparison or 'buyers guide' that I can post.

Although not realated to sensitometers, I am pleased with my two Tobias DENSITOMETERS (found for $25 for both). I have seen that the Tobias densitometers do not command the same prices on e-bay as the Mcbeth and others, however, it seem Tobias still supports the old densitometers. I was able to get some replacement parts for my older model right from the factory.

donbga · Mar 31, 2007

ic-racer said:
I really like my Wejex but I just picked up an EG&G Mark VI and am waiting for shippment.

I have had the Wejex apart to clean and restore it and I like the fact that there is no power supply (all AC) and it can easily be repaired and I am sure will last my lifetime.

In terms of the EG&G, I understand it uses a xenon flash circut, is that correct? Any resources for schematics or shop manuals for these units? The one I am getting supposedly is in proper working order, but if I am to rely on the device for any testing, I need to ensure that I can keep it running.

I know from experience that just trying to source a replacement capacitor for a Rollei E36RE Flash is impossible (mostly because the dimensions of the flash housing). I suspect that because the EG&G Mark IV has a bigger housing, aftermarket parts replacement options are better than a camera photoflash.

Although it was mentioned that the EG&G is the only one really designed for continuous tone b&w film, the Wejex I have does have a 'white' light source. Basically it is a white bulb and I have an 80A filter in the filter slot.

I'd like to get both densitometers together and do a side by side comparison or 'buyers guide' that I can post.

Although not realated to sensitometers, I am pleased with my two Tobias DENSITOMETERS (found for $25 for both). I have seen that the Tobias densitometers do not command the same prices on e-bay as the Mcbeth and others, however, it seem Tobias still supports the old densitometers. I was able to get some replacement parts for my older model right from the factory.

Where did you get the EG&G?

ic-racer · Mar 31, 2007

EG&G vs WEJEX

Got it on e-bay. There were some other biders, I guess you were not one of them as they let me have it for $13. I was just looking for a broken one to play around with and compare with the WEJEX, but the one that I won supposedly is in working condition. I also got my WEJEX on e-bay a few years ago.

Keep checking e-bay, I have seen quite a few of both WEJEX and EG&G show up. I would think that even though a lot of them have gone for cheap, bidding up to $100 to $150 is reasonable because, compared to the rest of one's equipment $150 is still cheap for something that has a lot of value to the practicing silver-based artist. I did pay $125 for my WEJEX, it was in good working order, I did take it apart to clean it up and see how it works.

I like fixing stuff so I don't have much problem buying stuff on e-bay. I just expect it to be broken when I get it. If it really works then I am not dissappointed. (except for electroinic cameras, though)

MAGNAchrom · Mar 31, 2007

donbga said:
I'm curious to know if anyone is using a sensitometer for BTZS film testing?

Jorge Gasteozoro is a big fan of using a sensitometer as part of his BTZS methodology. I'm sure he would be happy to hear from you directly. You can also consult his in-depth article by downloading the 2nd issue of MAGNAchrom for free.

sanking · Mar 31, 2007

ic-racer said:
I'd like to get both densitometers together and do a side by side comparison or 'buyers guide' that I can post.

I also have a Wejex. It originally came with a step wedge of only 11 steps so I tore that out and put in a small Stouffer that has 21 steps.

You do have to take into account reciprocity failure. The unit I have gives exposures of 2.5 seconds. However, this fact may actually be a plus for persons working with LF and ULF cameras since we often expose in this range.

I bought the Wejex basically for postage since there were no bids on the one I got. They come up quite often. The EG&G is less common, but you see one every month or so on EBAY. I got the EG&G for the low reserve of $50 or so since there no other bids. The EG&G Mark VI and VII is a Xenon type flash sensitometer, with adjustable speeds but I believe 1/100 or 1/1000 is the minimum speed.

Some films have much more reciprocity failure than others in range of 2.5 seconds to 1/1000 of a second so you should expect different results in terms of speed and contrast.

Sandy

donbga · Mar 31, 2007

MAGNAchrom said:
Jorge Gasteozoro is a big fan of using a sensitometer as part of his BTZS methodology. I'm sure he would be happy to hear from you directly. You can also consult his in-depth article by downloading the 2nd issue of MAGNAchrom for free.

Thanks Michael. I know Jorge and I'm familiar with BTZS. I just need/want a repeatable consistent exposure method for testing. I'm really not a testing hound but I would like to be able to accurately dial in 3 or 4 emulsions. A few weeks ago I finally realized that using an enlarger isn't the optimum light source since I watched my quartz halogen bulb in my Saunders 4500 fade to black in a matter of minutes. I realized then I had been chasing my tail.

Of course one could purchase a Metro Lux but for BTZS testing I think a sensitometer is the best way to go. A friend of mine here in Atlanta has one and I may borrow his until I can find my own.

Best regards,

Don

P.S. I am looking forward to using the spread sheet you developed even though I have all of the BTZS software. The spread sheet would be especially convenient if you can incorporate a 31 step tablet. Having 0.10 log density steps makes plotting a bit smoother and accurate, IMO

magic823 · Mar 31, 2007

So you were the one that outbid me. The seller was going to put in an extra line filter for me. I was going to keep it and then sell the unit here since I already own a Mark VII.

BTW, I have an owners manual and schematic for the Mark VI and VII. If he sends extra line filters to you, I'll trade you for a copy (Line filters are used just above the flash tube to attenuate the flash output. I have one, but I'd like a complete set. You can use ND filters in place of them.) The owners manuals are harder to come by than the units themselves.

Steve

ic-racer said:
Got it on e-bay. There were some other biders, I guess you were not one of them as they let me have it for $13. I was just looking for a broken one to play around with and compare with the WEJEX, but the one that I won supposedly is in working condition. I also got my WEJEX on e-bay a few years ago.

Keep checking e-bay, I have seen quite a few of both WEJEX and EG&G show up. I would think that even though a lot of them have gone for cheap, bidding up to $100 to $150 is reasonable because, compared to the rest of one's equipment $150 is still cheap for something that has a lot of value to the practicing silver-based artist. I did pay $125 for my WEJEX, it was in good working order, I did take it apart to clean it up and see how it works.

I like fixing stuff so I don't have much problem buying stuff on e-bay. I just expect it to be broken when I get it. If it really works then I am not dissappointed. (except for electroinic cameras, though)

MAGNAchrom · Mar 31, 2007

donbga said:
P.S. I am looking forward to using the spread sheet you developed even though I have all of the BTZS software. The spread sheet would be especially convenient if you can incorporate a 31 step tablet. Having 0.10 log density steps makes plotting a bit smoother and accurate, IMO

So I have a question: As I am somewhat intimately familiar with the underlying math behind the curves, the SBR curves (and the following is my opinion based on my observations on the underlying math, and in no way questions the premise of BTZS methodology) are only mathematically "accurate" when the film and processing is close to "normal" and they start to deviate from predicitability due to introduced non-linearity as the contrast deviates from 1.05. This is why Phil Davis mentioned to me that he had to resort to adding lookup tables to keep the SBR curves meaningful. In short, it appears his initial math for the SBR curves did not match his observed results with high contrast negs, so it would make sense that he supplemented the rendering of the SBR curves (in essence, tweaking them) with recorded data from his own experiments.

As such, how would making a "smoother" curve make your utilization of the plotted data "more accurate"? It seems to me -- spoken as someone who is clearly from the outside -- that the essence of the BTZS plots is to get you "close enough" with the result of more predictible negatives, not necessarily more perfect negatives (if there even is such a thing).

ic-racer · Mar 31, 2007

sanking said:
I also have a Wejex. It originally came with a step wedge of only 11 steps so I tore that out and put in a small Stouffer that has 21 steps.

That is interesting about the 11 step wedge in the Wejex. Mine came with a 21 glued in under the glass. I was able to measure all the steps with the densitometer, saving me the pain of trying to replace the stepwedge.

It seem like my Wejex gives a 1 second exposure (I think the shutter is only open for about 1 second of the entire buzzing cycle) but I will time it exactly to make up a comparison chart between the Wejex and EG&G.

If reciprocity failure is of any concern probably depends on how one is using the sensitometry data.

This is a quote from Kodak:
"The Reciprocity Law usually applies quite well for exposure times of 1/5 to 1/1000 second for black-and-white films. Above and below these speeds, black-and-white films are subject to reciprocity failure. When the law does not hold, underexposure and change in contrast occur."

Seems to indicate "some change in contrast can occur" also. In real life conditions I suspect any change in contrast between 1/125 of a second and 1 second would be very small in comparison to big changes in contrast like comparing N to N+1, N-1, etc. (True, experts out there?)

Either way, in my system I don't think the sensitometer exposure duration affects anything because I am just checking slopes of film "known to be processed correctly" (ie prints fine at 35M 35Y or so) and comparing it to an "unknown" film/developer combination. I kind of wanted to speed up the process of testing out new developer/film combinations. That is to say, the only question I am trying to answer is "What development time should I try for this new film/developer combination so that I can print the negatives on variable contrast paper and get good prints like I get with old favorites x,and y." So nothing to do with ISO, EI, Speed, Zones, Expansion, Contraction etc.

I would be interested in knowing how others are using their sensitometers.

Eric Rose · Mar 31, 2007

magic823 said:
You need a EG&G Mark V Sensitometer, not the X-Rite models that pop up on ebay. The EG&G models do popup ocassionally, I got mine there. There are several us us here that have them. I know Sandy King and I both do.

Steve

Why not an X-Rite?

magic823 · Mar 31, 2007

Eric Rose said:
Why not an X-Rite?

The X-Rites are designed for X-Ray film and only expose blue or green.

ic-racer · Mar 31, 2007

magic823 said:
The X-Rites are designed for X-Ray film and only expose blue or green.

The reason they are like this is that when taking x-rays of humans, they usually use an intensifying screen. This screen will phosphorosce or glow in green or blue (depending on the screen) when x-rays hit it. The screen is placed over the x-ray film (which is orthochromatic film). So rather than the x-rays themselves providing all the exposure to the film, the phosphoroscent screen exposes the film. Overall this contributes to a lower radiation dose for the patient. So, when using green screens they run control strips with the green light on the sensitometer,etc.

I suspect that they WOULD provide some usefull slope information with panchromatic film. One could probably test it and see if the slope with the green is different than that with the blue and infer that if they were similar that adding in the red would not change things much.

I would presume that modern films all have similar blue/green sensitivity, so speed comparisons would probably be close also.

So, I think for $25 they would be interesting to try. But for $250 you may be better off with EG&G, Wejex or something home made.

Another thing that would be fun to try is to repace some of the green and blue leds with red leds. Or replace a whole bank of green leds with 'white' leds.

If I can pick one up for $25 on e-pay I could test it against the Wejex and the EG&G and do a little "Mythbusters" thing to see for shure.

Eric Rose · Mar 31, 2007

magic823 said:
The X-Rites are designed for X-Ray film and only expose blue or green.

Mine does more than that. This is from their website:

361T Tabletop Transmission Densitometer

Measures density (up to 6.0D) and dot area. Used to linearize imagesetters, adjust exposure, perform processor quality control, verify duplicated or contacted films. UV mode measures film base fog and evaluates diazo films.

magic823 · Mar 31, 2007

Eric Rose said:
Mine does more than that. This is from their website:

361T Tabletop Transmission Densitometer

Measures density (up to 6.0D) and dot area. Used to linearize imagesetters, adjust exposure, perform processor quality control, verify duplicated or contacted films. UV mode measures film base fog and evaluates diazo films.

That's because we are talking about sensitometers, not densitometers. One exposes film (sensitometer) and the other measures film density (densitometer).

ic-racer · Mar 31, 2007

Eric Rose said:
Mine does more than that. This is from their website:

361T Tabletop Transmission Densitometer

Measures density (up to 6.0D) and dot area. Used to linearize imagesetters, adjust exposure, perform processor quality control, verify duplicated or contacted films. UV mode measures film base fog and evaluates diazo films.

That is a DENSITOMETER that you have.

Eric Rose · Apr 1, 2007

ooohhhh.

sanking · Apr 1, 2007

MAGNAchrom said:
As such, how would making a "smoother" curve make your utilization of the plotted data "more accurate"? It seems to me -- spoken as someone who is clearly from the outside -- that the essence of the BTZS plots is to get you "close enough" with the result of more predictible negatives, not necessarily more perfect negatives (if there even is such a thing).

One of my uses of Winplotter is to compare different film/developer combinations. Even if the curve is somewhat skewed by "look-up" tables the information derived from therelative comparison of film/developer combinations should be useful. And the advantage of the 31 steps is simply that it gives a closer and better defined look at the shape of the curve in the areas of the toe in the area that you are most interested in comparing.

Sandy King

Sensitometer for BTZS testing

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