Wait. Don’t do that. All your development times were fine here. All your film achieved it’s rated speed.
Consider the rated speed of film to be correct for determining exposure for all the example processes you graphed here.
Now you are free to “index” to the film speed to meet your favorite look. I suggest exposing as if film was 2/3 stop slower, not because I think the film is slower, but because greater exposure assures me of having adequate exposure.
I also want you to consider locking your “sensitometry” exposures to a couple choices. For example you were testing films with speeds of 400 and 100 but your exposures were varied. Don’t vary them. You will be able to read relative film speed off the graphs and it will be more apparent if you see the shift left for more sensitive film and right for slower film.
The reason to have a “fast film” and “slow film” setup is so the curve doesn’t fall off the edge of the paper.
Bill, 3.0D wedge contains 10 stops, so we evaluate film response across 10 stops range. Same exposure for 400 and 100 leaves 8 stops for the 400 film if exposure is well adjusted to contain the 100 film toe. 8 stops range is a bit narrow range if wanting to explore well the 400 film shoulder with same exposure. A 4.0D wedge would allow it better.Originally Posted by Bill Burk
Your proposition is a good choice, but let me propose an alternative: Just with a cheap ($20) lux meter we can adjust light intensity, so we have absolute units to plot each curve in the right place. Another way it would be to vary exposure time to the 1/4 for the 400 film, and then shifting the curve acordingly.
Time change it could be done if not using a filament lamp, but a CRI 98 LED lamp. The tungsten filament imposes a some 1 second exposure, because if longer then we have LIRF in the dense steps, and in shorter then we have inaccuracy from filament heating transitories.
My view is that a cheap lux-meter is a good gear addition, once we take the calibration effort... having the absolute exposure units is nice
Yup 10 stops are covered and the same light that gives you a good graph on 100 will get just the upper part of the curve for 400. So a couple major light intensity differences are good.
But I always say the light can be arbitrary as long as it’s consistent. The graphs will reveal the amount of light that hit the film.
The major point I was making about having two exposure setups for sensitometry instead of moving exposure about, is mostly for consistency and so you can learn to see the curves moving left and right. If you try to adjust exposure before you make each sensitometry test, you might get confused about what is happening.
So if the film is 80 or 64, you can use the same setup as for 100... if it's 320 or 200 use the same setup as for 400. As Pere said there's 10 stops in the step wedges we traditionally use. You really only need to land 7 or 8 stops of curve information to make a good graph. I'm only disappointed when my 400 speed film is overexposed by 2 stops and it makes the last reading above 0.10. (So I throw a 2-stop ND filter in the mix a lot of the time).
Anyway, younghoon has a good setup. I think it's daylight by camera shutter with adjustments for different speeds. That lends itself to either approach... you can try to hit the sweet spot of the curve every time. But I'm just saying don't. Instead choose the same f/stop and shutter speed where possible, picking one or two combinations as your favorites. Keep same shutter and change f/stop. Then the possibility that 1/125 and 1/500 are not exactly two stops apart won't mess up your tests (compared to when you using 1/125 all the time with f/8 and f/16). Let the curves move around a bit just so they don't fall off the paper or above 0.10
Thankfully you kindly and aggressively explained it, but I did not understand it well.
So I am very sorry for you.
That's why I'm trying to learn from the basics.
And I'm reading your posts again and again.
I have Stuffer 4x5-31 Step Wedge, X-Rite 341 Transmission Densitometer, Sekonic L-858D Light Meter and Sekonic Exposure Profile Target II.
So if I continue studying and doing various exercises, I think I can understand it.
Thank you very much.
Chamonix 45N-2, Chamonix 45H-1
Once I shot (a roll of 35mm) a Step Wedge, my black and white dog in the outdoors, and a Sekonic Exposure Profile target on the same roll of film.
Since it's developed at one time, the graph of the step wedge, and the densities I read from different parts of my dog, and densities of different patches of the exposure profile target can all be graphed on the same chart page.
Here's what the graph looks like. I learned a lot from this test. You could try something just like it.
Greetings. I've just tried to determine a suitable speed for Ilford FP4+ (4x5, box speed 125), developed in EcoPro's Xtol clone (diluted 1:1), using Paul Wainwright's method in the PDF titled "Use Your Eyes!". Using a Stouffer 21-step tablet, I exposed negatives to doubled sheets of white bond paper in direct sun, with my Wista 45SP + Rodenstock Ronar 240mm f9 lens focused at infinity but only 18" from the white sheet. I checked that the film filled the GG, and metered for Zone X (Minolta Spotmeter M, checked recently against a Nikon DSLR as an approximate accuracy test) for successive exposures at ASA settings of 40, 50, 120, 160, 200, 250 and 320. With the exception of the ASA 200 exposure (which showed evidence of a light leak or other anomaly) the negatives showed a steady progression in steps 21 and 20 toward a closer match to the film base + fog strip (a tape-obscured spot on the step tablet that blocked sunlight from the negative). Only at ASA 320 was step 21 very close to FB + fog, and there was a very slight density change from step 20 to step 21. I think these two indicators satisfy "Use Your Eyes" for film speed determination.
The few shooting descriptions that I've read in the past that gave speed ratings for FP4+ in Xtol have named speeds LOWER than box speed, which makes me question the figure I'm getting. The progression of my results seems pretty convincing though. I haven't shot any film since I performed these tests (today), so field verification awaits. I wonder if anyone has rated FP4+ in Xtol or Legacy Pro 1:1 at higher than box speeds?
Hi tomwilliams,
There are two chief reasons for Zone System photographers to downrate film (for example use IE 64 with ISO 125 film).
1. The speed point from metered point in the Zone System is 4 stops (1.2) whereas ISO metered point to speed point is 10x (1.0).
2. They like additional shadow detail above the standard ISO exposure would give.
A third reason may be that the real reason is 1. but they don't know it so they think the reason is 2.
Bill, greetings. I don't recall that any of those folks who mentioned that they down-rated FP4+ in Xtol also mentioned their motives.
I've read a number of the posts that precede mine in this thread, and observe that the conversation is substantially more advanced than I can follow. I didn't understand your post, at least in part because the nomenclature is unfamiliar.
I did notice that Kodak says to expect a slight increase in film speed in xtol 1:1, but my stop and a third increase doesn't strike me as 'slight'.
Posting Permissions
Reply With Quote
Bookmarks