David William Whites way of testing exposure

[martin s]

Hey there,

David William White explained how to test a combination of development times and exposures in order to achieve better results. The post is to be found here.

I wanted to give it a shot today, since I just underexposed two rolls of (new to me) APX 400. For the test I rated the film at 400 and shot a roll, bracketing every shot (-2,-1,0,1,2). The one in the middle is the one properly exposed according to the built in meter (Leica m6). I developed the film in Rodinal 1+25 for 10 minutes, at 21°C.

To me it looks like +2 is "properly" exposed, wouldn't that mean I'd have to rate the film at ASA 100 if I develop for 10 minutes? What would be the next step in order to get ASA 400? Develop a little longer, if so, how much longer?

Regarding 'Whites' and the use of apostrophes, I have no clue if there's supposed to be one and if yes - where.

I appreciate any input.martin

 

[dfoo]

How did you get that contact sheet above? Was it from an enlarger, or a scanner?

 

[martin s]

Ah I forgot to mention, I scanned the negative in strips of 5 disabling all the software-related functions like auto-levels or anything similar. I have no clue how to do contact sheets, I'd give it a try though if it's necessary?

martin

 

[dfoo]

If you print contact sheets with suitable exposure (that you have found the exposure point at which the film base is rendered black) you have something which is constant, upon which you can then base future decisions.

With scanners this isn't really so. There are many variables, such as your monitor, the scanner, and processing done to the image.

Also your images don't really have alot of dynamic range. It might be better to setup a test shot including a solid black, a solid white and a gray card. With this you can better see how the exposure really looks with these lighting conditions... Your aim would be to have suitable shadow detail, highlights and the gray at medium density.

 

[Benjamin Marks]

I was going to say what dfoo said. When doing test strips for printing a contact sheet, I would typically expose for the first frame where the sprocket holes went black. That is, at that exposure, you are printing though "film base plus fog" to get to your first true black with minimal loss of highlight detail. This is particularly important where (as I think I am inferring from your OP) film is going to be your "capture medium" and you are deciding on a basic development time (a decision that will have an important effect on all the images produced with this set up). Acknowleging that film and sensors don't record the world in the same way, you want to preserve as much detail as you can on that film. Adding to the development time is only going to block up your highlights, if you have chosen wrong. So even though it would be tempting to see the +2 stops as the ideal exposure above, I think you need to go back, photograph something with a lot of highlight detail (bracket as you have done) and then get someone with a wet darkroom to print you a good contact sheet so that you can make your decisions. For mopes like us, off the shelf scanners and monitors are not ideal for assessing film developer response, IMHO.

Best,

Ben Marks

 

[David William White]

Geez, glad to see someone making the effort! I'm a little clueless when it comes to scanners, and dfoo might be right, but it does look to me like +2 stops is very close to optimal, *if* this is the scanning regimen you use most. I guess if you find you are always boosting the exposure, brightness, and contrast of your scanned negatives, it would be better to increase exposure time, as your test has shown nicely. For your development time, +2 seems to result in a much better negative scan, and on a go-forward basis, you're much better off.

Just to see how linear your meter is, I would then go shoot just a nice puffy cloud sky at +2 and similarly expect wonderful negatives. If so, you're off to the races.

Benjamin makes a strong point about making sure you are able to get as much range as possible into your negatives. Development is the other factor, but my guess is you are not far off. Like dfoo and Benjamin, I'd be more comfortable and certain with contact sheets, but you have the 'system' now to find out what your optimum exposure and development times are for a wide variety of scanned negatives.

If you're not happy with your highlights at +2 and you get to dicking with development times, I'd just look at the push/pull times listed by your film manufacturer & for your developer. If you push or pull by one stop, and shoot the same scene under the same conditions, your scan should sit nicely below your first one, just shifted by one frame.

As always, switching film, cameras, developers, and, wow, meters, means retesting.

Best regards,

dww

 

[titrisol]

If you plan to scan all your negatives then check each of them individually for detail in the shadows from L to R
e.g. If 0 has already detail then that is your speed/development combo

to me the +1 has all the information
then you need to play with the levels/curves of your images