Density Opinion

[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.