Hp5 at ASA 141???

[Andrew O'Neill]

I shoot HP5 at 250 with most developers, but I remember using a developer (can't remember which one) back in the 90's where I had to use an EI of 160. You have to find what works. Not surprised in the least if EI 141 worked for you.

[neil poulsen]

Do your tests include a measure of contrast? Just curious if you judge film speed at the same development time that reaches 0.62 contrast. Or do you develop to Zone System classic "N" time which gives you a certain Zone IX density calibrated to your printing paper.

And also curious if you are doing classic Zone System speed test, where you meter and then stop down to Zone I.

The answer to those two questions can easily account for a stop from Box Speed. Then all that would have to happen for you to "lose" another half stop, is some deviation like choice of developer, minor processing mistakes like time and temperature...

In other words you are sane, it's not uncommon to find personal speeds that are different than manufacturer rated speed.

The classic Zone System speed test. I metered at ASA 400, and then stopped down to a Zone I. Thereafter, I took three more exposures, opening the aperture a half-stop for each. It's for the last sheet of film that I reported data (FB+f of 0.08 and 0.18 for my target reading, which of course is 0.1 above FB+f). I'm using D76 as a developer, switching from ID-11. So, I'm redoing my Zone system calibrations for the first time in years.

This is the first time that I've used my Zone VI modified meter for testing, which might account for the additional half-stop loss of speed. (Compared to my usual results of ASA 200.) I use daylight corrected bulbs to illuminate my test target, since I suspect that pan-chromatic b&w film is daylight corrected. If my meter performs as purported, I believe it may read the blue a little higher, since blue appears lighter in b&w prints. Thereby, this will close the f-stop a little for a Zone I, and require a little lower ASA to reach the 0.1 above FB+f standard.

[IanG]

The classic Zone System speed test. I metered at ASA 400, and then stopped down to a Zone I. Thereafter, I took three more exposures, opening the aperture a half-stop for each. It's for the last sheet of film that I reported data (FB+f of 0.08 and 0.18 for my target reading, which of course is 0.1 above FB+f). I'm using D76 as a developer, switching from ID-11. So, I'm redoing my Zone system calibrations for the first time in years.

This is the first time that I've used my Zone VI modified meter for testing, which might account for the additional half-stop loss of speed. (Compared to my usual results of ASA 200.) I use daylight corrected bulbs to illuminate my test target, since I suspect that pan-chromatic b&w film is daylight corrected.

Daylight corrected bulbs are not a good substitute for daylight, Ilford used to publish ISO speeds for daylight and artificial light, 400 daylight, 200 artificial light for HP5 so you've not run a valid test except for shooting with those particular lamps.

Ian

[w5ami]

The classic Zone System speed test. I metered at ASA 400, and then stopped down to a Zone I. Thereafter, I took three more exposures, opening the aperture a half-stop for each. It's for the last sheet of film that I reported data (FB+f of 0.08 and 0.18 for my target reading, which of course is 0.1 above FB+f). I'm using D76 as a developer, switching from ID-11. So, I'm redoing my Zone system calibrations for the first time in years.

This is the first time that I've used my Zone VI modified meter for testing, which might account for the additional half-stop loss of speed. (Compared to my usual results of ASA 200.) I use daylight corrected bulbs to illuminate my test target, since I suspect that pan-chromatic b&w film is daylight corrected. If my meter performs as purported, I believe it may read the blue a little higher, since blue appears lighter in b&w prints. Thereby, this will close the f-stop a little for a Zone I, and require a little lower ASA to reach the 0.1 above FB+f standard.

I would strongly suggest using real daylight if at all possible. A good evenly overcast day works great, but a open area with blue skies overhead and no direct sun works even better. All assuming you are film testing for mostly outdoor photos.

Brian

[ic-racer]

I thought that I would do a sanity check; mine!

But before you render an opinion, let me explain . . .

I just completed a speed test for Ilford's HP5, and determined that the speed of my box of film is ASA 141, which is a half-stop better than ASA 100, and of course a half-stop worse than ASA 200.

Is this consistent with the results that others have obtained? Normally, I come up with ASA 200, so I guess it isn't so far off of typical. But, I thought that I would check.

I've accurately taken into account bellows expansion and actual shutter speed. My FB+F was 0.08, and my target was 0.18. I checked my densitometer with a Stouffer's standard that I keep on hand, and it's accuracy appears to be satisfactory.

Most would interpret that as an "exposure index" test. It is not clear what you are using as a target, but if you can have the lens focused at 'infinity' you won't have to bother with a bellows extension calculation.

[ic-racer]

Unique Photo still carries color control strips (link), but did anyone ever make B&W control strips?

Most people make their own B&W control strips. You can cobble together a simple sensitometer without too much trouble.

[Mark Sampson]

Kodak made b/w control strips- they were very useful when I operated replenished sink-line processes. Not sure if they still do, though. I've never heard of anyone making their own b/w control strips. I suppose you could... but making them accurate and consistent enough to be valuable might well be more effort than it would be worth.

[ic-racer]

Critical sensitometry requires control of image latency, that is unavailable in these pre-made strips. "Development Process Control" strips like these that are made 'on-site' with a sensitometer have some advantages over the pre-made ones, such as reduced cost, improved obtainability, control of latency, control of film batch and type, etc.

[Bill Burk]

The classic Zone System speed test. I metered at ASA 400, and then stopped down to a Zone I. Thereafter, I took three more exposures, opening the aperture a half-stop for each. It's for the last sheet of film that I reported data (FB+f of 0.08 and 0.18 for my target reading, which of course is 0.1 above FB+f).

OK, then your speed is 142.2623528 according to my calculations. As others have pointed out, this is a "Blue Tungsten Bulb" speed.

That's -2.25 in log Meter Candle Seconds (arithmetic 0.005623413 Meter Candle Seconds).

Take 0.8 divided by 0.005623413 and you get the speed I calculated.

I would have been pleased to quote a time in terms of Pi or Square Root of 2, if that's how it would have worked out. But I don't think those familiar constants contribute to the right answer in this case.

neil poulsen,

The fact you obtained a "Blue Tungsten Bulb" speed shouldn't be too disconcerting. It's probably going to come in handy when you do some copy work. Then that's the right speed to use.

But for daylight landscapes, I think you might be better off assuming your old favorite speed "200" still applies.

[bbuszard]

But for daylight landscapes, I think you might be better off assuming your old favorite speed "200" still applies.

Perhaps, but my tests in daylight have produced results similar to Neil's. I shoot HP5+ at 160 (unless I'm shooting handheld). With FP4+, oddly enough, I can shoot at box speed. Same process for both films, using Xtol 1:1 at 24C.