Density Opinion

[Richard Ryerson]

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

[Nick_3536]

Does the 502 have a zero button? If it does could you have zeroed after taking the first reading?

[Richard Ryerson]

Nick,

It has a zero knob on the front and the calibrate screw on the back.

I have checked and double checked and triple checked the numbers. So the possibilities of advertently hitting the knob is slim to none.

Also, the zero knob requires many revolutions to show an affect. I bet it's on the order of .01 per revolution. Quite interesting.

Thanks and Best regards,

Rick

[Kirk Keyes]

If every step of your T3110 reads correctly, then you can eliminate the densitometer from the equation. How about metering - did you meter off the black card with the spot meter? Did you account for lens extension in the exposure. If you are metering with a spot meter, and then focussing the lens for a short distance, you need to add some time to the exposure. Perhaps your meter reads high? How did it compare to the meter in the Canon? (The Canon built in meter would have corrected for the lens extension.) Maybe your effective film speed is less than 50? Try doing a series of exposures for all the zones and plot the data out.

[jose angel]

Considering that all the process is correct with a densitometer made for B/W films, and the densitometer is reset to zero onto the blank area of the film, a difference in 0.01dLog from B+F to zone I shows an underexposed or underdeveloped film.

If reseting is not possible, and your reading is based on that blank (unexposed) area of the film, results are the same subtracting 0.21 to your readings.

I develop films with a Jobo processor. In my experience, the damn TMX is a very low speed film. I must expose it from 32 to 64 ASA to obtain a bit of shadow detail in "normal" situations. I haven´t here my data charts, but I try to remember that my "N" developing time is around 8-10 minutes at 21ºC -in the Jobo-. It makes me think that you are underexposing at least 2/3 stop and probably underdeveloping your film.

[jose angel]

What about your readings of zone VIII?

[John Cook]

Lots to cover here. But just a few thoughts:

The zero adjustment on most densitometers I have used usually has much more of a hair trigger than that. Just touching the knob will cause the needle to jump.

Second, you didn't mention warm-up time. May not be the prime issue in this case, but just so you know. Densitometers drift like crazy. Very unstable when cold. Nearly impossible to get the same series of readings twice in a row. Before using, turn the unit on and allow it to warm internally for a prolonged period. At least five or ten minutes, maybe more.

Next, I can't seem to figure out your ISO rating from your comments. Should be 2/3 to a full stop more exposure than manufacturer's rating. At least that's where ALL of my tests have wound up over the years.

Some day, you will make a perfect negative of a perfect exposure. You can then reverse-engineer that film to determine your ideal H&D curve for your equipment and materials. If it will help, I find that a Zone I density of 0.1 over bd+f and a Zone VII density of 0.8 over bd+f to work well for sunlit scenes printed on my Omega D5 with condenser head on Ilford VC paper with no printing filter. You may start there, if you like. Or not...

[Richard Ryerson]

Kirk:

Yeah, I don't think the densitometer is a player in the problem. As far as lens extension factor, I racked the focus out to infinity to have no extension. Granted there may be something there, due to the inaccuracies in manufacture, but this was used in all tests.

Given that I would expect some definitely notable differences in the seperate E.I. tests.

I can't compare the spot to the F1 meter considering that the F1 meter is b-roke. Hasn't worked since I got it. A primary reason for purchasing the F1 to force me to think about what I am doing.

Jose:

I did record the Zone V and Zone VIII densities in my log, but I was more focused on the Zone I considering that comes first. Find the right EI and then work on the dev time densities. I put them all on the same roll to see what the results were. Maybe I would get lucky and the Zone VIII density would show 1.2 over Zone I for the proper Zone I of .1 over FB+F. Or maybe I would be lucky enough to see the required dev time change by looking at the differences in the I, V and VIII data.

I am at work now and drudging up the numbers from memory. So please bear with me.

100 EI Test
FB+F .21

Zone I .22 / .01 over FB+F

Zone V .53 / .32 over FB+F

Zone VIII .90 / .69 over FB+F

50 EI Test
FB+F .21

Zone I .23 / .02 over FB+F

Zone V .73 / .52 over FB+F

Zone VIII 1.3 / 1.1 over FB+F

I "think" these are the numbers. I could be wrong however, but not by much.

John:

Warm up time - Sorry I failed to mention it, it slipped my mind. Being a new piece of equipment I decided to check this variable out too. And I noticed only a slight change in reading, .01 over a couple of minutes. And then it remains stable for the duration.

I did constantly retest the step wedge to see if it was changing. After the warm up adjustment, it remained constant.

The ISO rating of the film is 100. I agree that the EI will probably be 2/3 to 1 stop less exposure. This will put the rating at 64 or 50. But the issue with my tests is the Zone I densities aren't anywhere near anything tested. Im not looking for dead nuts on, just ballpark.

All:

I wanted to throw this problem out to everyone to see what jumps to mind first or foremost, before I use my spot meter as a paper weight.

While the spot meter is new to me also, the readings I get from it are very reasonable. Meaning that if it's off, it's not much. Sunny 16 medium subject shows about 14 2/3 EV. Which is a little more exposure than f/16 @ 1/125 with 100 ISO.

Since there are a few opinions now, here is what I think could be the problem.

1. The meter - The meter is reading the low light black paper incorrectly thinking it's a brighter subject than it is. 20% probability

2. The camera - The shutter speed I was could be defunct. 25% probability.

3. The camera - The lens mount or lens itself is so far off that that amount of light passing through doesnt comply (at all) with the focal ratio/aperture scale. 1% probablility

4. I/O error - Idiot Operator - The Zone I numbers sure look like Zone 0 numbers, don't they? I guess it's possible I closed down 5 stops instead of 4 when setting up for Zone I. 50% probability (yes I am giving myself some credit, the other 4% is unknown ;) lol )

Thanks,

Rick

[Richard Ryerson]

Another thread raises another possibility here too.

Do you think that I may have the wrong sized cloggs? what size did AA wear?

[jose angel]

Richard, I asked you about the zone VIII to knows about developing time... that I think is in the reasonable way. When exposed to 50ASA, zone VIII is 1.1 over B+F, which is credible (a bit overdeveloped to my liking). It would mean that film is underexposed, but hard to think... I couldn´t ensure it without a new test. Next time, I would expose the film to 25-32 ASA and develop for a 5-10% less. I suppose that developer is fresh.

The next thing that came to my mind is the black card. Theoretically it must work, but is probably that you are squeezing the conditions to the extreme. I would repeat the test with a near 18% reflectance subject.

In my case, I´m sure the reason would be the last one! In the XXL version!

[James E Galvin]

I wonder about the black card. It may be that reflection is an issue, can you see any reflection highlights on the card? That is, is it even slightly glossy? If so, the meter and camera must be in the same place so they see it equally.
I second the suggestion to use a grey card, or even a white one. I've had trouble with reflections on a grey card that was not perfectly matte.
Also with the black card, you're testing the flair in the meter, that is does it completely ignore bright light outside of its circle? Ditto go to grey card.

[jose angel]

Everybody knows that the clogg issue is just when printing.

[neil poulsen]

What I notice is that there's not much difference between ASA50 and ASA100. One would expect a greater difference.

What camera are you using exposing for the the test shots? Also, what lens and shutter? Have you had the shutter checked for consistency?

When I did calibrations for HP5, I picked a lens and shutter speed that was dead-on consistent.

[Richard Schlesinger]

If you look at Dr. Richard Henry's book on Controls in Black and White he has a really simple way to calibrate your spot meter using a GE soft white light bulb. Apparently these are extremely consistent in output and with acouple of neutral density filters you can pretty much cover the whole range. This would at least eliminate your meter as a source of error.

[Richard Ryerson]

Neil:

I couldn't agree more. One would expect to see some signifigant changes in the density. Unless, the exposure settings were set to less than zone i tones; in which case that would put these densities in the 'toe' of the curve. And as the system goes, any changes to dev time would not signifigantly change the low density areas.

As far as the accuracy goes, eh so so. There isn't any reason for me to suspect that a speed is off much. I've take quite a few frames with the camera and the results have been "nice" and nothing surprising.

But when I do my next test I will set it up on my home made shutter speed tester.

Richard:

Could you explain more on Dr. Henry's method of calibrating the spot meters? Doing a check online for the book results in people selling copies for as much as $200.00. So I won't be securing a copy for at least a couple hours. ;) (Side note: Just curious really, film speed test are designed to take inaccuracies in equipment in account)

Everyone:

Thanks for all the posts. The more I read this thread and digest the content. The more I am thinking that it's either a stupid photographer error by setting the wrong aperture or that the shutter speed is way bad at that particular speed.

I think I will look into the shutter speeds and then find the gray card tomorrow. But this time, I think I am only going to expose the Zone I exposures and a single FB+F to save time and effort until I find the right speed. Then find the right dev time.

Another personal opinion request. Given this thread, does it mean I am a magic bullet chaser?

Best regards,

Rick

[James Meckley]

If I remember correctly, Dr. Henry's calibration method for spot meters requires use of a particular GE light bulb (output in lumens specified) which hasn't been available for nearly a decade.

[Jorge Gasteazoro]

I think your problem is metering the black card. Some meters are more suceptible to IR emissions that others, in addition measuring at the limits of the meter might introduce a greater degree of error than measuring at the "middle". I say a do over with a gray card or at least a blank wall would be better than trying to find out the porblem with this test.

[phil sweeney]

your fb+f density sure sounds high (0.21). though I have never used max 100, I would expect fb+f to be 0.04 to 0.1. It takes a lot of dev time to get 0.1 fb+f!

[Conrad Hoffman]

This should be easy stuff, as your understandings seem just fine. First, use a white card, not black. Accuracy will be difficult with a black card. There's no need for 18% either. Meter and go four stops down. With an EI of half to 3/4 the box speed, you should get 0.1 over base plus fog. To the eye, that looks like a low but very perceptible density. IMO, once you "tune" your eye to this amount of density you don't even need the densitometer!

[Richard Schlesinger]

I had no idea Dr. Henry's book was so valuable. For those of you who are interested Dr. Henry (he lived within rock throwing distance of AA) was an MD and a Ph.D. chemist with, I think, his own business. At any rate, he has all the qualifications to have been well trained in scientific methodology. He did this book, in which he writes up many of his investigations involving b&w film and his findings in processing etc. He lists his equipment for testing, and he apparently obtained some really top quality instrumentation.

He got into light meters (partof his film testing stuff) and wrote up his communications with manufacturers, ANSI (if memory serves) and Fred Picker among others. He had "personal communications" he cites with people at GE regarding the consistency of their soft white 100 watt bulb. GE says they are very consistent in output (I forget the number of lumens - if anyone wishes I'll be glad to check this stuff and post the information). Anyway, he (Henry) found at 29' 2" , set up as he carefully describes, this bulb reads, I think, 15 on his Pentax spot meter. Given the number of lumens it then is easy to check if the meter is reading correctly. With the use of a couple of ND filters one can then check the meter across its whole range. Since one can check the bulb against Dr. Henry's reading it becomes a simple matter to determine if your meter is off, and if so how much. He doesn't go into adjusting the meter. Better left to people with expertise.

Again, according to Dr. Henry (he cites communication with manufacturers etc.) there is a lot of confusion in the of light meters, with a lot of variation etc.

I hope this answers your question - I'll be happy to check stuff in my copy of the book, and fill in whatever blanks I have left. Looking at my bulb, it is a GE soft white with "87" appearing with the wattage and voltage printed on the end of the bulb. I seem to have purchased mine in April of '99.

[tim atherton]

"I had no idea Dr. Henry's book was so valuable"

there are plenty of copies for sale from $27+ to $75+

[Craig Schroeder]

Richard... I couldn't recall reading the GE Soft White routine in Henry's book and pulled my copy out just now. I can't quickly find the calibrating info and can't locate a reference in the index that sends me there. Where in the book is it? Is this bulb quite consistent over varying voltages? It certainly runs against one's instinct that this could be accurate but I certainly have respected Richard Henry's thoroughness of technique. The book is a fascinating read and after some years, this has me reading it again.

[Richard Schlesinger]

I have found the book extremely valuable, and often wondered why I seldom/never see references to it. At any rate, in the 2nd edition, beginning on page 167 he discusses light meters and his correspondence with Hideki Kondo, Chief, Research Laboratory, Japan Camera and Optical Instruments and Testing Institute. And a bunch of other people, and outlines what he learned about light meters (a very great deal).

On page 177 he describes a set up for checking calibration of a 1* spot meter using a GE Longlife White Lamp Bulb 100V 1585 Lumens. There is a diagram of the setup. He suggests using an inexpensive simple voltmeter (Radio Shack $10 - $20) plugged into the other half of a dual outlet to check the voltage at the time of testing, and gives corrections if the voltage is below 114 or above 121.

I hope this helps. If anyone wants the whole business on calibrating light meters I can probably manage it - though I'm something of a Luddite and don't know how to do much more than e-mail on a computer. Seeing the price of the book now, I can understand not wanting to spend $121. On the other hand there is a great deal of still useful information in the book, even though his testing was limited to Tri-X Professional roll film. Just reading his methodology is an education!

[Richard Schlesinger]

I wasn't aware of the changes at GE, but it is not surprising. Thinking about it, given the setup described 29'2" from the bulb for the meter, I think I would fool around with different bulbs until I found one where my meter would read the 15 Richard Henry found at that distance. By definition, I think, one would then have a bulb putting out 1585? lumens and, checking the voltage as directed and using ND filters, voila, a cheap and easy meter check for both accuracy and linearity.

[Brian Ellis]

I'd suggest making two changes in the way you're conducting the tests though I don't know whether either will necessarily solve your problem.

First, using a black card isn't a good idea. In theory it shouldn't matter since in theory the meter takes the density of the card into account in determining your exposures so that you should be able to use a black card, a white card, or anything in between but in practice things don't work exactly as they should in theory. Use something closer to neutral rather than a black (or a white)card. A gray card is nice but not a necessity, if you can't find one use a piece of cardboard from a box or something else that isn't overly dark or white, just make sure the surface is smooth.

Second, I don't exactly understand how you're conducting these tests. Zone V doesn't usually enter into film speed and development tests (at least not as I learned the testing methodology). But apart from that, why are you testing for three different zones, particularly Zone VIII, simultaneously with your film speed testing.? The normal procedure, or at least the one I was taught, is to determine your film speed by exposing for Zone I only, processing for the manufacturer's recommended time, then after you've established your film speed do your development time testing based on Zone VIII only.

[Richard Ryerson]

Hey all!

Thanks for the great info. It's helped in my testing tremendously.

Everyone really seems to think the black card is the culprit here so I found my gray card and did some more tests this weekend. So I found the gray card, tested the full range again and resulted in densities that you'd expect to see. WOOO HOOO a breack through!

The EI 50 test for Zone I was .07 over FB+F so I tested from EI 50 to EI 25 again. Haven't developed those negs. But I will let you know.

I will try to answer the questions that posters asked of me. Sorry they arent directed back to the poster, there are a few and I am pressed for time here.

Why test FB+F, Zone's I, V and VIII? Well I am new to the Zone System and that was the recommendation in AA's The Negative (recent edition) The value as I see it is that it will show you where your normal time results. It will not affect the Zone I density.

Why is the FB+F density so high? In a nutshell, I believe this is due to the fact that it's roll film 35mm. I don't know the exact expected values for TMAX 100 / D76 @ 1:1. I do know that the smaller the format, the greater the FB+F densities. Large Format you may get .02, medium format you may get .1, 35mm I am getting .21

I don't think that I am cooking the negatives too long in the soup. I am using the recommend times of 8:30 @ 20C exactly. I know this time will probably change, but it wouldn't represent such a bad value for Zone I, unless they were cooked over night.

Thanks again all!

Rick

PS. Just to let you guys know, I didn't spend all my photographic time doing tests this weekend. We had a local event for the schools activities (we are having budget problems, don't get me started) They had bands, vendors, contests, water activities, and a lot more. At any rate, my wife and I went and had a great time. I was able to shoot about 10 rolls throughout the day. Haven't 'souped' them yet.

Just thought I'd point out that even though we look for the devil in the details, we shouldn't forget the big picture.

[Todd Schoenbaum]

Just a few comments:

I think Fred Picker did recommend using a black card (or a gray card in deep shade) for the Zone I tests as this most accurately reproduces the values of objects that will be placed at Zone I. The idea was that meters may not be consistent over a range. But, now that I think about it more this doesnt seem to be all that great of an idea as sometimes objects with an EV of 9 may be placed at Zone I, and other times objects with EVs as low as 1. Still trying a Zone I test on a white board in open sunlight might be pushing it.

As for the FB+F being so high, this may be due to bad film. I have seen this happen when film is exposed to high temperatures (this may be your doing or transport or shop storage).

Testing shutters: While it wont give you the exact times, the following may help tell you if your shutters are consistent across the board and between lenses. Shoot for Zone V at varying aperature / shutter speed combinations and then check the values on the densitometer. The closer the values are, the more consistent your shutters are.

Also when shooting your Zone I tests, it has been recommended that there be a few sheets of higher Zone values in the tank so as to avoid an excess of developer in the solution.

Best of luck