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.

[Doremus Scudder]

Or your meter could simply be not as linear as you would want, resulting in more exposure in the more brightly-lit scene. If you're sure of your shutter speeds, and the exposure difference is apparent over the entire range of tones and not just the lower values, then this is the most likely explanation.

Best,

Doremus

[Bill Burk]

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.

It's flare all right. Adams doesn't address it much but he was aware of it. in one video he shows a negative of Garrapata beach and says "flare helped the shadows as expected". It reduces your negative density range, which will actually make your high-key negative easier to print.

Imagine you are in a dark room and a friend shines a light in your eyes. No matter how you try, you will not be able to see your friend because the flare has illuminated your retina in general. It's like you lit up the whole room, there's no part of the room that's dark any more.

I don't know if it's the right word for it but I think "aerial flare" would be a good description.

And you could alter your EI in response to it, but I think you would be chasing a difficult to predict scenario.

[faberryman]

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 concur. It is easy to say "I placed my shadows in Zone III" when they are actually Zone II or Zone IV. Your eye just needs to be calibrated through experience. Sounds like you have a good technical footing. Hang in there.

[Ulophot]

Or your meter could simply be not as linear as you would want, resulting in more exposure in the more brightly-lit scene. If you're sure of your shutter speeds, and the exposure difference is apparent over the entire range of tones and not just the lower values, then this is the most likely explanation.

Best,

Doremus

That makes sense. I am only a bit surprised as the meter was cleaned, adjusted, and calibrated by Richard Ritter, who handled modifications of the meter for Zone VI; that, however, does not obviate your observation, a variable I had forgotten to consider. Meters have a kinship with many thermometers in this respect. Thank you.

[Bill Burk]

You might create a "black box" - a cardboard box painted black or covered with black cloth inside with an opening cut out of the front.

You might think this box always meters 0 or shows on film as same as unexposed film.

But the meter will show some reading, and the film will show some exposure, and this would be due to flare.

Your test result might have been caused by a slow shutter speed. From a distance, your spot meter may have indicated a reading that includes flare (if your reading up-close is different than the reading from camera position you can tell how much is flare).

[John Layton]

So many variables playing into this...and over time I have been so very thankful to threads such as this one which have served so well to help me improve my own craft.

But there is one particular aspect of measuring light with a spot meter, which I feel deserves a bit more attention from us...which some might see as splitting hairs - and others may have already compensated for…either deliberately or intuitively.

As much as I love my Zone-6 modified Pentax spot meter...I've also found, especially when out in the field, that its almost impossible (for me) to truly isolate a specific density in a given scene. Most of what I see - even within my light meter's one degree spot...is full of various micro-densities and/or zonal shifts (imagine anything remotely spherical) - and I truly believe that this contributes significantly to the visibly broader "zonal spectra" in my negatives than that which I'd originally been able to “evaluate” with my meter. Of course there are a host of other variables which all affect our zonal spectra…both as perceived by us and as realized in our results - which have been well covered on these threads.

I bring up the above not only to simply add this variable to the mix of other more well established ones…but also to lament the long-ago passing of the SEI photometer…which, IMHO, provided the only truly effective means for reaching into a scene and providing an actual, isolated EV…limited only by a practitioners ability to perceive detail.

For those unfamiliar with the SEI meter…it provides, in its field of view, a one-half degree “spot” which is actually a bulb-lit patch, the brightness of which, when aimed at the desired area of evaluation, is then adjusted with a rheostat until its intensity matches whatever detail within the patch which is of interest to the photographer. Lets imagine, for example, a fine, sunlit branch against a shadowed background…not only could the SEI isolate this branch, but…to the extent that the user could perceive this…it could allow further evaluation of any modulation of light over the branch itself - even if the branch occupied a small fraction of the area of the light patch! This is why I’d earlier placed the word spot in quotes…because the SEI's capacity to separate out EV’s extends to well within the patch itself.

I own an SEI meter - paid 15 bucks at a yard sale…but it worked only briefly, just long enough for me to realize what a wonderful tool this could be, and long enough to truly wonder why the light measurement principle upon which this meter was based had not been embraced more broadly within the photographic industry. To be honest, the SEI, as wonderful as it was, was also large, heavy, slow, awkward. But when I think of how its technology could have been taken foreward...especially thinking of those of us for whom making accurate measurements is key - I have to wonder!

[Jerry Bodine]

...I own an SEI meter - paid 15 bucks at a yard sale…but it worked only briefly, just long enough for me to realize what a wonderful tool this could be, and long enough to truly wonder why the light measurement principle upon which this meter was based had not been embraced more broadly within the photographic industry...

John – I also have an SEI meter, purchased new at my first AA Yosemite Workshop in ’66. I also got the anti-flare tube and extra bulb for it (just in case). It’s still functional. The anti-flare tube is about 3” long, black on the interior, that slips onto the meter’s telescopic optics; it has an orifice at its tip that blocks out much of the FOV around the spot. When I do my film speed tests with a white mount board target, I use a 31-step Stouffer against the film and a bellows shade to minimize camera/lens flare, then meter the board with the SEI and place the reading on Zone X. I’ve punched a hole in the step wedge to yield the Zone X density that includes fb+fog. The rebate density isolates the fog; I can then plot the characteristic curve as Net Density vs Zone.

I certainly concur with your description as the large/heavy/slow/awkward; it rivals a 3 D-cell aluminum flashlight.

[chassis]

A suggestion to increase understanding - record again the same 2 scenes with towels, foil, etc. using incident metering and constant EI.

[Ulophot]

Chassis, an interesting suggestion, which I'll fold in to my continued explorations. My inclination at present is to try Marris's method to confirm my spot meter's linearity over the 8-stop or so range involved in my test. Ritter is such a fine technician that I suspect my own error may somehow be playing into all this more, but it could just be a chance in the meter (which was around a long time before it reached me) and this will be a useful check. Years ago as an active professional, I experimented a fair amount with my Gossen(s) between reflected and incident, and read numerous articles about tuning one's incident-reading craft in angular lighting conditions.

By employing the flat t-shirt cloth, my test was designed to minimize potential discrepancies between what reflected and incident readings would yield; the towel, of course, responds quite differently to the side light from the window. As others above have noted, however, "micro-" reflections from fibers in a woven fabric can surprise. Were the difference not so great as my results have indicated, I wouldn't worry about it. As one who cut his proverbial teeth in 35mm journalistic work, printing "imperfect" negatives is not new to me. I look forward to continuing to hone my craft with help from the good folks in this forum.

[John Layton]

Philip your post above reminds me of a Zone System course I taught years ago...which began with my handing out a (cheap) grey card to each student. When out in the field with these cards - I realized that results were all over the place...due to the amount of specularity exhibited by these cards - grrr! I then found a fancier one...forget who makes this, but its called "the Last Grey Card," (Bogen I think?) - which has an almost non-specular surface.

[Ulophot]

Philip your post above reminds me of a Zone System course I taught years ago...which began with my handing out a (cheap) grey card to each student. When out in the field with these cards - I realized that results were all over the place...due to the amount of specularity exhibited by these cards - grrr! I then found a fancier one...forget who makes this, but its called "the Last Grey Card," (Bogen I think?) - which has an almost non-specular surface.

Thanks, John, I'll keep it in mind.

This morning, I spoke with another local LF photographer, Jim Stewart (beautiful work, https://jrileystewart.com/), who also mentioned -- unprompted-- meter linearity. He said that he had had flare problems with a Sekonic spot meter and had drilled a hole in the lens cap for it, large enough to allow full vision of the spot field, and that this significantly reduced the problem, though he said it dropped the reading about 2 stops.

Adams writes about making a cardboard tube, matte black inside, also to reduce flare. I may give this a try, though in the circumstances I have been measuring, the sun was at my back. Perhaps it will cutting internal flare from more-than-frame-filling high-value subjects.

[chassis]

This article by Sekonic on metering technique helped me. Maybe it helps others.

https://www.sekonic.com/united-states/classroom/meteringtechniques/incidentvsreflected.aspx

[Bill Burk]

I don’t think flare in a spotmeter is a particularly bad thing. Flare that reaches the spotmeter sensor is similar to flare that would reach the film so maybe the reading will be a fair predictor of what you will achieve on film anyway.

[Bruce Barlow]

I think you should learn to judge exposure without a meter. Under conditions that are predictable, walk around, look at things, guess the shutter speed and aperture. Then use your meter to see if you're accurate, and learn why not, if you're off. No pictures, just looking. You can do this anytime, anywhere. Carry your spotmeter around with you.

Ask yourself questions: What's the difference between bright sun and shadows? How does an overcast day differ from a sunny day? What's the difference between early morning and noon? Late afternoon? Once you find the answers for yourself, you'll know them for life, if not longer.

Afterwards, every time you make an exposure, guess the settings before you meter the scene. Then meter it to see if you're correct.

You'll be decent at it after an hour of wandering around. You'll rarely miss after a month of photographing.

And remember, blue sky on a clear sunny day is pretty much always Zone V. Close enough for photography.

[Ulophot]

Mystery solved!

Special thanks again to Doremus for suggesting meter linearity-departure, and for Maris for his testing technique. I used the latter tonight and got results precisely matching the over-exposure I have been getting in bright exterior scenes. The meter is quite linear in the typical LF range from longer exposures to 1/15 @ 22 or equivalent at ISO 400. Beyond that, linearity-departure begins, leading to more than a stop over-exposure in less than two stops of illumination increase.

That noted, I do agree with Bruce regarding learning the light, something I was not bad at back in my Leica M4 journalism days. Before there were meters, there was photography, and a few minor hobbyists, such as Edward Weston, Paul Strand, and W. Eugene Smith managed to produce some pretty good work without them as well. All artists benefit from knowing their materials.

Again, thanks to all who responded.