Exposure variance by overall conditions

[Ulophot]

In the course of recent exposure/development tests, as I have been working my way back into LF, I have found that my EI goes up significantly when I photograph lighter subjects outdoors, e.g., a light-painted house wall, white-painted door, filling a good part of the frame with most areas Zone V and above, as compared with, say, an indoor portrait in window light in which half or more of the frame is Zone IV and below. In the latter, EI 200 is just right, while the exteriors would have been fine at EI 400 -- I see a Zone III-read area coming up as IV in the neg.

I use a Tachihara Hope 4x5 with a 210 Komura Commercial, I shoot HP5+ and one developer. The bellows appears to be a replacement; the front is mounted slightly skewed. Shutter speeds were recently calibrated, as was my Pentax Zone VI-Modified Spotmeter. .

I checked Adams and Stroebel on flare last night. Adams speaks of bellows flare having potentially significant effects, but seems to indicate that the film edges may more affected, which is not my case. Perhaps it could be some overall lens flare, but I wouldn't expect this in the Komura, which, if I am not mistaken, is multicoated, and I have had it a long time; contrast appears good with no appearance of flare in subjects like a window light portrait including bright clothing, curtains, etc.

Any ideas? What other text might I devise? (I wish I could reverse the effect -- how nice it would be to get EI 400 inside!)

[Jac@stafford.net]

With respect and concern, your post covers a few issues. Can we narrow it down?

[Bruce Watson]

In the course of recent exposure/development tests, as I have been working my way back into LF, I have found that my EI goes up significantly when I photograph lighter subjects outdoors...

EI is not supposed to be a variable in that sense. It varies based on your workflow (developer, agitation, temperature, etc.) which is why we all have to test for our own personal EI (PEI). Before you ask, the ISO listed on the box is found by the manufacturer using a specific workflow and it's nicely repeatable. That is, if you'll replicate their workflow in your darkroom, you'll get the same ISO.

All that means is that there's some flaw in how you are running your tests. I suspect that it's really nothing more than an interpretation problem. That is, what you saw and metered as Zone III wasn't in fact Zone III in the tonality of the scene. This is one of the reasons I spent so much time learning to use my old Pentax 1 degree spot meter.

[Vaughn]

If there is a lot of light being scattered about in all directions -- sunlight reflecting off white walls, but also under the bright diffused light of a light fog -- perhaps a lens hood would be an advantage even with a MC lens to minimize flare. I do not have them for every lens and end up using the darkcloth as best I can.

Sounds like you are gaining a solid understanding of your exposure/development system...good luck!

[Leigh]

Film e.i. changes ONLY if your darkroom process changes.

Your perception of "zones" can vary dramatically, as in extremely.
It takes a lot of practice to evaluate tonality accurately.
If your results differ from your analysis, it's the analysis that's wrong.

- Leigh

[Doremus Scudder]

Overall flare can easily add a stop to the lowest value(s) in the negative. It has little or no effect on the higher values. You'll notice that the flarey negs will have less separation in the low values, but more density, somewhat approximating a film with a long toe. Flare acts a bit like flashing your film; it raises the sensitivity by bringing the threshold sensitivity up a bit, hence your different E.I.s.

Most of your flare is likely coming from the bellows scattering the light from excess coverage. In this case, a lens hood/compendium shade will help a lot. Your next test: with and without lens shade outdoors with bright subjects.

Best,

Doremus

[Ulophot]

Thanks to all. I suspect that it is my interpretations; using a spot meter is fairly new to me, and that may well be the weak link in my process chain. I am aware of the difference between ISO and EI, and that the EI should not be a variable. The lens does have fairly large coverage, and a compendium hood, rather than the round one that came with the lens might make a difference, though I don't have the means to get one at present. Again, however, contrast appears good, and all values seem to be affected (as I should have made clear in my OP), so spot-user error may well be the culprit.

I shall perform a carefully controlled test today and return with results, embarrassing or not. (I say embarrassing, by no means to denigrate continuous learning, but only because I was a professional for more than 30 years before having to put my cameras down for more than a decade, and I had my processes under very good control then. I have started back in with a different 4x5, meter, and developer, and have been working methodically through the many variables. I just didn't expect some of the anomalies I have encountered, given my level of experience.)

[Luis-F-S]

Did you determine your EI and development time based on Zone I being 0.1 Density above fb+f (EI)and Zone VII being 1.15 density above fb+f (development time)? That's the starting point and unless this is done, you cannot narrow down much. When I do this, I use ND filters such as to eliminate aperture errors and don't vary the shutter speed. Meter an evenly lit surface that won't change and place in in Zone VII (open 2 stop from the spot meter reading). Make an exposure, then use this setting and add 1.8 ND filters to get to Zone I. I expose both readings on the same piece of film by using a dark slide cut in half or you can use splitters on the camera. L

[Ulophot]

Again, my thanks to all respondents. I appreciate that variables abound; I'm doing my best to cover them.

My testing has never involved densitometric readings, which I know will be heresy to some and simply a fudge factor for others. I also don't have a negative scanner, so I cannot show you such scans. If you are still reading, here is how I tested this morning, as shown in the two attached images of prints from my flatbed scanner. Please refer to my original post, above, if you have not, to understand what I was testing for.

Two scenes, one exterior, one interior, using the same test target. The target was black t-shirt material stretched over black foam core, a piece of black flocking paper, a low-saturation blue towel, and a piece of aluminum foil for creating high-value highlights.

Using my spot meter along the camera lens axis, I placed the t-shirt on Zone I, with the meter set to ISO 400, even though I have consistently been using 200 based on previous decades of work, and on a lot of retesting over the past 8 months with D23. That rating of Zone I at EI 200 is based on achieving visible difference from black in a print made at Grade 2 with my standard papers when clear film just prints black.

Exterior: The flocking paper fell on O; the towel on IV; the foil highlights from VII up to about X or more, as closely as I could tell (some may have been higher). The sunlit white pillar face fell on VI, the shaded face on V. Exposure was 1/125 @ f/32 minus a quarter stop, with illumination confirmed at the moment of exposure. The exposure determination included mutually cancelling factors: the shutter runs a quarter-stop slow at 1/125, and the bellows extension called for ¼ stop extra exposure. In other words, since these cancelled each other, I used the meter reading to place the shirt on Zone I.

Interior: The window light from the right was not as even, of course. The shirt area below the flocking paper was placed on Zone I, the paper fell on 0; the towel between III and IV; foil highlights VIII and above. The curtain behind the set-up fell on V and VI; the wall area behind and above the foil fell on III. Distance was maintained constant, exposure was ½ @ F/22 minus ¼, the quarter being the bellows extension factor. (A quarter stop is not very meaningful in practical B&W negative photography, but I'm trying to account for every variable here.)

The two sheets were developed together in a Stearman SP-445 for my Normal development. (For the curious, D23 1:1, 9 minutes, 68˚F, 6 initial inversions (15 seconds), then 4 per minute (10 seconds). The solution gained 1˚ during development, as measured when poured out.). Stop and fix normal.

The negatives show even more clearly what the attached prints (unmanipulated, printed identically) show—a generous stop more density in the exterior image, which is how this thread got started. (The line in the exterior image is a cut I made prior to scanning, to compare some tones more closely.)

Comparing: In the interior, the Zone I border with 0 can be seen in the negative, but disappears in the print, while in the exterior, 0 is practically a good 1½ and the shirt well separated above that. (The flocking paper had a mottled appearance with lighter blotches, but did read 0.) The interior towel (flat left area as read) is perhaps a ½ zone short of expected; the exterior, is better than a stop higher than read. In the interior, the curtain values are in range, likewise the foil, while outside the pillar values are a good stop brighter than read; likewise, the foil.

Although I had no reason to think that the shutter has suddenly gotten a full stop slower at 1/125, nor about that much faster at the slower speeds, I then ran a quick test to confirm it. I didn't have conditions allowing a comparison of the two speeds used for the images, but I took identical shots at 1/125 and 1/30, compensating with the aperture, and developed them together. The negative densities are the same. And the 1/2-second speed, audibly, seems accurate, certainly not a 1/4-second.

As I said, the negatives show the difference in the lowest values more clearly. The attached scans appear as if their black is only a dark gray; playing with digital levels is not my purpose here.

I remain open to suggestions explaining my results, pointing out flaws in my testing, or simply sending me cheerily off to get more familiar with my spot meter.

[Pere Casals]

I have found that my EI goes up significantly when I photograph lighter subjects outdoors

> First you probably use a different range of shutter speeds when shooting outdoors. Shutter speeds of mechanical shutters had a +/- 30% tolerance when sold new, with time it can be more difference, so a 1/30 marked can be 1/20 or 1/40, and this is a full stop. Use a shutter tester ($15 to $100) to know real speeds.



> Films have usually different sensitivity to different regions in the spectrum, so it can be more or less sensitive to one kind of light that has more blue or red (etc..), for example Ortho or Orthopancromatic films doesn't see less red end, so depending on the spectral dominance of your lightning (SPD. spectral power distribution) you may have to vary your metering.

> A photometer may read different depending on its own sensitivity to different regions (colors) of the spectrum, a photometer that emulates the human eye sensitivity may have a lot of sensitivity in the green, so for excample if you illuminate with a green light then the meterinmg is to underexpose.

> Then it comes all the complexity with filters vs metering vs film spectral sensitivity.


All that was well solved with color film and modern meters like the Nikon F5 one, it has 1005 RGB matrix, that doesn't fail, (almost) never. When metering for a view camera we should add a bit the inteligent calculations that the F5 makes.