Alessandro, do you have a thermometer yet?
Alessandro, do you have a thermometer yet?
One man's Mede is another man's Persian.
Hello!
Thank you very much for your response!
I still haven't performed the test as I still need to find the time to go and buy the thermometer, so it would be worthless...
Thank you very much for all the explanation and I'll let you know for sure the results!
Hi Alessandro,
It's good you decided to postpone testing until you get a thermometer.
Running 20 degree C water over my fingers gives me a sensation of coolness with occasional veins of warmth. It's like I feel tiny streams of hot water rippling through that haven't mixed completely with the mainstream of mostly cold water.
I tested how accurate I can be the past few days. I got 24, 20 and 16 degrees C. So without a thermometer my temperature would vary by +/- 4 degrees C. This is "out of control" for black and white processing. I consider variation of +/- 2 degrees C as "under control."
Assuming you can feel for "warmer" and then develop longer, try a negative or two and see if they start looking better. This could give you the confidence to continue.
Other factors could also be working against you:
Bellows extension: Focus at infinity for test shots. When shooting close-up, you need to give more exposure depending on lens-to-film distance.
Flat lighting: "Normal" is a subject with some important parts in shade and other parts in sunlight. In the studio with your one light, everything might be evenly lit. To compensate for flat lighting, develop longer than "Normal". How much longer will be determined by those development time tests that you will do later.
Maybe you have a flash meter, but if not and if you are going to be using electronic flash extensively for your work, I would suggest strongly that you purchase a good flash meter. They are of course available new, but you can buy good used ones as well. I have used the Minolta 3, Minolta 4, Minolta 5, and I currently have a Minolta 6. All worked very well for me.
In using black and white film before I had a densitomiter I just made a proper proof and carefully looked at it to determine whether I needed to change the ISO to give either more of less exposure. Remember though that in general, exposure controls the low values, and development controls the high values. So you want to get your low values looking correct by changing your ISO setting, and then, after you get that correct, you want to change your development to control your high values.
The reason I suggest that you use a flash meter is becasue of the Inverse Square Law.
It is much easier to use a flash meter than to figure out the expsosure taking into account the inverse square law. (if you move your lights)
As you will recall, the inverse square law says that light falls off at the square of the change in distance. As an example. if you first have a flash at 10 feet and get a proper exposure at that distance, and then you move the light to 20 feet, you have now doubled the distance, but the light has falled off 4 times (2 squared) or 2 stops, not 1 stop. This concept is very important when using flash, and contrary to what many people think, shutter speed is important when using flash, especially if you have areas that are not being illuminated by the flash. In those cases, you will need to drag the shutter in order to take advantage of the ambient light hitting those areas.
When testing for EI, I'd consider +- 2c (a range of 4c or 7.6f) uacceptable. The idea here is to eliminate all possible variables. Agitation is very important as well. I'd try for +- 1f when making tests in trays, it's no big deal to keep it even closer if you're using tanks.Originally Posted by Bill Burk
One man's Mede is another man's Persian.
Right, E. von Hoegh
I meant to illustrate that by feel, temperature would be out of control - and that an expensive, highly accurate thermometer is not required for Black and White processing.
I also confused F and C scales. +/- 1 degree C (or +/- 2 degrees F) are reasonable process control limits for normal everday processing.
But while testing it would be important to work to tighter limits. Write down the exact temperature reading off the thermometer. And while testing it would be good to stay within process control limits of +/- 1 degree F if you can get that level of accuracy.
Cool.
Feeling temperature is so subjective as to be useless. Come inside with cold fingers and 45f water will feel warm. As for a thermometer, it just has to be consistent, and most glass tube thermometers are.
I'll grant that I'm a bit fanatical about things, but I just don't see why I should leave any more to chance than neccesary. The making of the photo carries enough uncontrollable variables; I'll control the ones I can.
One man's Mede is another man's Persian.
Hi, Alessandro,
This was the old Zone VI (Fred Picker) recommendation, from his Newsletter #46. The procedure was created thru results from the workshops they gave (trying to get decent results from a wide range of participants):
1. In the film speed test, as someone else said, you're looking for a Zone I value that gives you density in the negative of about 0.10 over film base + fog. It's a perceptable value.
2. One aim is to eleminate as many of the variables from your test procedure as possible.
3. Test outdoors. Don't use flash or lights. As Thornton has said, it can be very hard to find a day where there is uniform lighting. So wait for a clear afternoon or a day of constant overcast. (In Vancouver area this past month, this has been a real challenge!)
4. Zone I is dark, so choose a dark, even-toned target placed in even shadow. I used a sheet of black craft cardboard from the local dollar store. If using fabric, watch out for wrinkles. Watch out for weird reflections. Place the target so it won't move in any breeze.
5. Use your best light meter. One camera, on a tripod. One lens.
6. Focus the lens on infinity, because you don't want texture in the image. On a view camera, that means the extension is equal to the focal length (6 inches for a 150mm lens). But it's easiest to simply focus on infinity in the real world and then point your camera to the target. Taking care not to let the focus change when you move the camera.
7. Depending on your preference, you'll be making 5 (my version) or maybe 7 (Picker version) exposures, plus one unexposed sheet (to measure film base + fog). Alternatively, on one sheet, you can pull the dark slide say 1/3 of the way out, though that does create a variation that sticklers will complain about.
8. Be sure the target completely fills the field of view of the lens.
9. Be sure to meter in line with your camera lens. Be careful not to let any shadow from the meter or yourself fall onto the target, or interfere with illumination coming from behind you and reaching the target. Check that the illumination is even across the target (all 4 corners), and adjust if needed.
10. Get ready to move reasonably quickly, to minimize the risk of the light changing or something else going wrong.
11. Set your meter on 1/2 of the manufacturer's film speed (eg, 160 if testing 320 speed film). This is for the 5 shot version. Set it on 1/4 the speed if doing the 8 shot version (eg, 80 for 320 speed film).
12. Take a test meter reading, to see where your exposure series will hit. You will be using only *one* shutter speed, because shutters aren't reliable, particularly in view camera lenses. For the choice of shutter speed, use a mid-range speed, not the bottom or top speeds.
13. You'll be making one-half stop exposures, starting with a wide aperture (eg, 5,6) and moving smaller (eg, 11). Choose the combination that will allow you to change the aperture, while using the same shutter speed for all exposures. You might do a test run, without exposing film, to get familiar with how you'll set the half stop aperture settings.
14. Meter the card for real this time and set your Zone I exposure. Don't take notes during the test. The half stop differences are easy to see in the negatives.
15. Make your first exposure. Then close down 1/2 a stop and make the second exposure. And so on until you've done all 5 sheets (1 stop below, 1/2 stop below, at box, 1/2 stop above, 1 stop above) or 7 sheets (2 stops below to 1 stop above).
16. Develop all negatives, plus the unexposed negative, at the very same time for your usual time and procedure. Development does affect the low values, but not as much as high values.
17. Lay out the processed negatives from darkest to clear. In the ideal world, you find a lab with a densitometer and get them to measure the negs. If two negs are close, choose the one with the slightly higher exposure (you're testing in half stops, but your meter will be set in 1/3 stops, so you can go a little higher or lower).
18. If you have some kind of reflected light spot meter, you can perhaps improvise a relative densitometer reading (this is me, not Picker):
a) tape a big enough piece of plain white paper to a window (even light, and watch the background that it's even), to diffuse the light; this is done better in even shade, not in sunlight; but it needs to be bright enough that the light meter is not hitting at the bottom or top of its indicator
b) tape the clear neg to the paper
c) the other negs probably have enough density difference that you can tell a couple are much too dark, and couple might be about right; choose those negs to tape up on the paper beside the clear neg
d) with a decent light meter, each stop means a difference of 0.3 in density, or 0.1 for each 1/3 stop (we know this because that's how neutral density filters are sold: 0.3 = 1 stop; 0.6 = 2 stops, and so on)
e) you can meter the clear neg to get a base number (eg, EV 8), which is the fb+f density (relative, not absolute)
f) then meter the other negs; this is a little fiddly, as the difference you're looking for is only 1/3 of a stop: eg, 7-2/3 on the EV scale, or just a hair more.
g) If you read all the negs, they serve as a check on each other -- the light meter reading should show a 2 stop total range, whihc is 0.6.
Should be close enough for government work. The sticklers in the crowd won't like it, and will find something more precise. When you shoot your next negs, include one neg at the newly found, tested speed as a Zone I exposure, to make sure you're getting repeatable results. If not, then adjust.
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