Underexposure and spot-metering

Christophe

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I am seeking some help here in working out what I did wrong the other day. I wanted to work on spot metering with a roll of FP4 medium format at 100. Images were around an aqueduct on an overcast morning, placing the darkest part of the shadows under the arches at Zone 3 (just barely enough texture for the brickwork). The highlights were between Zone 8 and 9 so quite a wide spread, but they were not dominant in the image, the overcast was such that I expected the highlights to be bright (it was a test) and I wanted the texture in the brickwork shadows. I developed in Ilfotec HC at 8 mn.

Of the 10 images, only the last 3 (of trees with no highlights) were exposed properly, dense with the Zone 3 being exactly as I was expecting. However, the first 7 images were massively under-exposed, very thin negatives, with some unworkable and others being a splodge of muddy darks when scanned. I believe that:
1) the main problem was how I metered the scenes and/or the dynamic range was too wide?; or
2) less probably, insufficient development time, but that would then have impacted the properly exposed negatives. I would be able to adjust for this with sheet film.

I took quite a few notes as it was something of a test, but despite spending some time reading up on this, I am still slightly unsure of the main culprit apart from myself of course (ahem, especially if I misread the meter and exposed at 1/2 instead of 2 seconds, although I don't think that I would have done this for all 7).

I should be grateful for some orientation or education (a slap upside the head might help, but please be gentle); the more I read, the more potential culprits appear, but I strongly suspect that I have not quite understood something very basic. If it helps, I can post some pictures of the negatives.

Thanks in advance,
Christophe
 

David M

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Some images would help, of course.
Operator error is the first thing to consider.* As you say, you might have set the wrong times. I think everybody has misread the "2" for two seconds as the "2" for a half. You might have set the wrong aperture, particularly if it was awkward to reach that little lever. You might have been using a different film – all dark slides look the same when loaded. It's possible that your spot meter was reading a different tone – if you were aiming at a small patch, there may have been brighter patch nearby and flare in the system altered the reading. Had you accidentally set the wrong EI for the first seven?
Were the negs developed together at the same time?
I'm sure there are other and more exotic mistakes, but I haven't learned how to make them yet.

* If it's Operator error, that's a good thing, because Operator can put it right. If it's the fairies, who knows? Remember, you are not alone, but many us keep quiet. In any case, it's not really error, but alternative learning
 

Ian-Barber

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David has mentioned some good points as I understand it you was using Roll film so the Darkslide bit may be irrelevant.

If the texture in the brickwork was the most important factor of the image, I would have been very close to it when I took the spot reading to ensure I was hitting the spot in question.

If you were unable to get that close then I may have placed them on Zone 4 just to give me some wiggle room and then brought them down later.

Some examples would be nice to see
 

Christophe

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Indeed, I was using roll film (120). I don't know how to insert coloured arrows or circles so hopefully it makes some sense. This is the straight scanned image, although I may have slightly adjusted it in the scan software. I metered with a Pentax spotmeter as follows (according to my notes):

Zone 5 -> in the 'v' of the central supporting arch facing out (where it flares out to support the railway);
Zone 4 -> the left hand underside of the arch on the right (to the right of the 'v');
Zone 3 -> the darkest underside of the arch on the right.



-970w.jpg

Some of the other images are underexposed much worse. On the upside, the last three images were properly metered. I am rather embarrassed that the first image I upload here is the above (exposure, composition, the lot), but I am going to swallow my pride to try and learn from this.
 

Alan Clark

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We hear a lot about pinpointing the darkest part of the subject where you want some texture to appear in the print, then taking an exposure reading from it and stopping down 2 stops to establish your exposure. I have to say I abandoned this idea many moons ago. Too much can go wrong. It relies on personal subjective judgement for a start. Picking the right spot to take a reading from can be quite difficult, and it's easy to make a mistake. Sometimes you can't separate out a zone 3 area to take a reading from. And the problem gets worse with a general scene, where close-up detail is actually too far away to take an accurate reading from.
I think the answer to all these problems is to use a Kodak grey card, or its equivalent. If you hold this up vertically in the shadows, so no sun or directional light falls on it then you have something to take a reading from which you can rely on as being Zone 5. And this gives you your exposure. Because the card is in the shadows, it relates to the shadows, and your exposure will give you shadow detail. (Move the grey card into the sun and its value will probably go up by 2 stops. If you base your exposure on this you will under-expose the shadows by 2 stops.)
Having worked out the exposure with the grey card, you can, of course, take readings from the highlights to work out the brightness range of the subject, in order to work out a suitable development time.
I said you can use the equivalent of a grey card. I actually use the cloth bag that my tiny Seconic Twinmate came in. This is mid-grey. And I take readings with the twinmate, not a spotmeter. All very simple.

Alan
 

Ian Grant

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I think you're getting the placements wrong and are under exposing by a couple of stops. Two factors you really need to do some simple Zone System tests to determine optimal Film speed and Normal development time. My own experience with Ilfotec HC and FP4 was it's true speed was more like 64-80EI.

One reason for doing tests is your meter may be slightly off calibration, as can shutter speeds, so personal testing takes variations into account.

Personally I would meter the area that you call Zone V as Zone 4, you are a good 2 + stops under exposed in this shot. I do my initial EI and dev time tests with 35mm film as I can clip off a few frames and these days 35mm emulsions match those of 120 and LF (they didn't use to).

While I've used Spotmeters for over 30 years I also carry an incident meter, I've found 99 times out of 100 I'd still use the same EV setting.

Ian
 

David M

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A good point.
You could certainly use an incident meter. For most subjects they work very well as long as you hold them in the right place.
In this case, the subject brightness range of the subject – that is, the bridge – is actually quite small and the those patches of sky form the high-zone part. As it has no interesting clouds, you could probably have let it go and apportioned the extra zones to the stonework.
I suggest that you've made a perfectly sensible decision on exposure, based on the range in the scene, but only if the sky had carried significant detail. Ian's suggestion of taking readings in two ways and comparing is a very good one.
There seems to be some flare at top left.
Please don't apologise. I think you can see that we are delighted. Nobody gets into LF if they don't enjoy solving problems.

If I may comment on composition, although you didn't ask... That triangle of branches and sky is intrusive and tells us nothing about the bridge and its situation that isn't evident elsewhere. I know how easy is to suggest standing somewhere else and taking a different picture, so I won't mention it.

I didn't spot that you were using roll film.
 

Ian Grant

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When I started using the Zone System it was with a Weston Euromaster in reflective mode (without the Invercone), Ansel Adams describes how to do this in "The Negative".

It might be a good idea to use an 18% Grey card as a reference, that's a Zone V you can take a spot-meter or reflective reading off, otherwise grass or the back of my hand is a good substitute.

Ian
 

Christophe

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Thank you all, really really appreciate the feedback and advice. There are certainly so many variables in exposing an image, but stumbling (or in this case, face planting!) on exposure is one of the more frustrating ones.

Picking the right spot to take a reading from can be quite difficult, and it's easy to make a mistake. Sometimes you can't separate out a zone 3 area to take a reading from. And the problem gets worse with a general scene, where close-up detail is actually too far away to take an accurate reading from.
Completely agree. I have generally found that Zone 5 is always slightly darker than what I think or see. I have a sticker on the Spotmeter with the different zones which helps remind me of what shade they should be, but it is small. All of the responses suggest that what I metered as Z5 should have been Z4 which I now see.

Two factors you really need to do some simple Zone System tests to determine optimal Film speed and Normal development time. My own experience with Ilfotec HC and FP4 was it's true speed was more like 64-80EI.
I have mainly been using HP5 (135 and 120) with Ilfotec HC and I think that this is the second roll of FP4 I have used (last time was in 2003...) so it was a "sacrificial" roll as I wanted to test two things: film speed and spot metering. In the reading up after I developed the film, I did see that many rate FP4 at 64-80EI so will factor that in. As to the development time, I will need to test with sheet film as 3 of the exposures on the roll were properly exposed, but I would not be able to adjust development time on a roll. I just understood as I type this what you meant about cutting up 35mm film for testing. I ordered some Pyrocat HD so will start testing with that rather than Ilfotec HC.

While I've used Spotmeters for over 30 years I also carry an incident meter, I've found 99 times out of 100 I'd still use the same EV setting.
I have only been using a spotmeter since earlier this year so on a learning curve. I believe that it is 1/3 stop over exposing, but I am not sure how critical that is with negatives (but would be an issue with slide). I did have my incident meter with me, but did not use it as I wanted to see the result exclusively with a spotmeter. This said, it would probably have been good to compare readings and make notes as an additional data point and will experiment further with that.

You have all commented on a grey card. I do have one, although it is pocket sized, but will incorporate using it or the back of my hand as a means of cross-checking my exposure.

If I may comment on composition, although you didn't ask... That triangle of branches and sky is intrusive and tells us nothing about the bridge and its situation that isn't evident elsewhere. I know how easy is to suggest standing somewhere else and taking a different picture, so I won't mention it.
None of the exposures on the entire roll would have gone further than a scan. I put this one up as it best illustrated the exposure errors (some of the others were barely silhouettes). This said, I genuinely do appreciate the feedback and fully agree with your comments. Indeed, it reminded me that even if I am doing a test, it is not an excuse to get lazy on composition (actually inexcusable) and it is easy to self-delude oneself about the quality of an image (although I knew this one was poor :)).
 

Ian Grant

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I'd check your Spotmeter against another Spotmeter if you know someone who has one, see how much they differ. If it's off it'll need adjusting, I think it's reading too high giving part of the underexposure.

Ian
 

Alan Clark

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I would also check the back of your hand against the back of Ian's hand. Ian said he uses his as a substitute for a grey card. But the back of my hand is one stop brighter than a grey card.....Must be all the washing up I do....

Alan
 

Alan9940

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I would also check the back of your hand against the back of Ian's hand. Ian said he uses his as a substitute for a grey card. But the back of my hand is one stop brighter than a grey card.....Must be all the washing up I do....

Alan
:D Me, too! I always knew I was too white!! :D

Another minor point to consider is with the spot meter itself. Meters don't all respond the same to different colors. Many years ago, Fred Picker tested this theory with a number of meters and found variations of up to 1 or more stops. He offered a service to modify Pentax and Soligor spot meters to include baffling for flare and filters to eliminate the color response variation. He also sold modified and tested meters. Not saying that one of these is necessary to get accurate exposures; rather simply mentioning a possible issue that can affect exposure.

All that said, though, if you do some simple testing (as suggested above) using your meter, camera, etc, then many of these variables can be mitigated. If you have or have access to a darkroom, learn about making a "Proper Proof." This simple "tool" will go a long way toward controlling your process. No idea how you would go about this technique via scanning and the desktop. If you have nailed your personal EI for a film and know what development will provide proper highlights, then placing a shadow area on Zone III shouldn't be an issue.
 

thronobulax

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Much good advice here so far. Allow me to add a little backstory. Many years ago (late 1950s - early 1960s) the standard for determining ASA changed from what exposure will give a satisfactory image to what is the minimum exposure required to register on the film. Overnight, the speed published on the box essentially doubled.

ASA should therefore not be understood to be meaningful as an absolute photographic measure, but rather as a comparison of sensitivity, much like - say - manufacturers' estimates of automobile mileage per gallon.


I have conducted a lot of sensiometric tests on a variety of film and developer combinations. Almost without exception, the "real" ASA of film (the exposure required to get 0.1 Density Unit above Film Base + Fog density) is approximately 1/2 the stated box ASA. This assumes an accurate meter, shutter, thermometers, etc.

My consistent experience is that when I suggest that people expose at the "1/2 of box ASA" heuristic, they get far better negatives. For most developers, I also decrease published development times about 20%. I'm told this is not necessarily appropriate for all developers - Pyrocat-HD comes to mind - but for HC-110, D-76, and DK-50, this is about right.

Modern films have great latitude and can withstand overexposure far better than underexposure. You cannot print what is not there, but you can print "through" high density negatives.

The other recommendation I have is to get into the habit of using distilled water for mixing developer. I have seen as much as 1 f/stop variability in film speed in seasonal water variations in my municipality.
 

Ian Grant

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I would also check the back of your hand against the back of Ian's hand. Ian said he uses his as a substitute for a grey card. But the back of my hand is one stop brighter than a grey card.....Must be all the washing up I do....

Alan
Changes slightly Summer to Winter :D It's an old trick I was taught using a Weston meter back in the late 1960's it's a crude ball park method. but was within a 1/3 of a stop compared to an 18% Grey card for me.

Ian
 

Ian Grant

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Much good advice here so far. Allow me to add a little backstory. Many years ago (late 1950s - early 1960s) the standard for determining ASA changed from what exposure will give a satisfactory image to what is the minimum exposure required to register on the film. Overnight, the speed published on the box essentially doubled.

ASA should therefore not be understood to be meaningful as an absolute photographic measure, but rather as a comparison of sensitivity, much like - say - manufacturers' estimates of automobile mileage per gallon.


I have conducted a lot of sensiometric tests on a variety of film and developer combinations. Almost without exception, the "real" ASA of film (the exposure required to get 0.1 Density Unit above Film Base + Fog density) is approximately 1/2 the stated box ASA. This assumes an accurate meter, shutter, thermometers, etc.

My consistent experience is that when I suggest that people expose at the "1/2 of box ASA" heuristic, they get far better negatives. For most developers, I also decrease published development times about 20%. I'm told this is not necessarily appropriate for all developers - Pyrocat-HD comes to mind - but for HC-110, D-76, and DK-50, this is about right.

Modern films have great latitude and can withstand overexposure far better than underexposure. You cannot print what is not there, but you can print "through" high density negatives.

The other recommendation I have is to get into the habit of using distilled water for mixing developer. I have seen as much as 1 f/stop variability in film speed in seasonal water variations in my municipality.

The half the box speed usually assumes you are doing Zone System or BTZS tests. I've always used practical testing, initially as descrive by Ansel Adams to setermine personal EI and development time, later a slight variant taught here in the UK that came from Minor White.

It's very dependant on the films, Tmax 100 & 400 (original) were definitely half box speed as also recommended by John Sexton in various articles. Afa AP/APX100 and AP/APX25 were exactly box speed EFKE PL25 was twice the speed in the name but that was the Tungsten speed not Daylight.

In practice I would shoot APX100 @ 100EI. Tmax100 @ 50EI and EFKE PL25 @ 50EI and process for the same times in replenished Xtol or Rodinal at 1 to 100, sometimes mixed in the same tank,results were of nera identical contrast printing on the same paper grade.

Why the differences, Tmax was tested by the ASA system, this was updated in 1960 along with the BS (British Standard)speed, to remove the one stop safety factor, it was changed again to a practical approach because Tmax failed the official test procedure a very lab based method and couldn't reach box speed. Part of the issue with Tmax was the old ASA test developer doesn't really suit it. Kodak used a Phenidone (Dimezone-S) Ascorbic developer in their Research Labs for some years it was a forerunner of Xtol.

1607878313937.png

This Kodak Developer comparison chart shows the differences, Ilfotec HC/LC is the equivalent of HC-110.

In contrast Agfa and EFKE used the German DIN testing method far more practical based method reflecting actual use more closely than Kodaks older laboratory testing.

The Modern ISO speed allows a film to be tested by the ASA or DIN standard and a fixed conversion table so my roll of 120 Delta 4oo is marked ISO 400/27º. I wondered what Agfa recommended and foud this:

1607879305679.png

These weren't times I used, I used an older table slightly lower times and 1/3 stop slower speed. It's interesting that Agfa APX100 is double the speed of Tmax 100 exactly as I'd found and used for about 20 years.

Ian
 
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thronobulax

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I have tested APX 100 in all its variants - 35mm, 120, and 4x5 and consistently - all developers tested - show that half speed ASA was required to get to .1DU+FB+F.

Not sure what you mean by "practical testing". The tests above were exactly my "personal EI" given that I used my meter, thermometer, darkroom technique, etc.

My purpose in exposure is to have the Picture Taking Me give Darkroom Me lots of choices when printing. Half box ASA (as confirmed with densitometry) provides Darkroom Me with content from which to work in the shadows. I split VC print everything, so only the the most extreme lighting conditions do I do much N+- development. Assuming I have exposed correctly, I can get the desired outcomes simply by controlling local contrast on the print ... most of the time. Very long Subject Brightness Range situations call for N- and a further reduction in development.

It's also worth noting that my tests of Efke 100 confirm you findings, though. It really is ASA 100.

In any case, I'd prefer to err to over- rather than underexposure to ensure there is content from which to work.

Happy snaps ...
 

Ian Grant

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Ansel Adams gives a practical method of Zone System testing in the negative, here in the UK that late Peter Goldfield and others used a slight variation largely becasue photographers like Joshua Thomas Cooper, John Davies, Fay Godwin and most of all John Blakemore print flatter with more tonality than Ansel Adams.

Jonh Blakemore's playful use of the Zone System is also practical and in his book Black & White Photography Workshop. He's probably the finest exponent of the Zone System.

Ian
 

Ian-Barber

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Jonh Blakemore's playful use of the Zone System is also practical and in his book Black & White Photography Workshop. He's probably the finest exponent of the Zone System.
Without going back and re visiting John Blakemore's and The Negative book, what does John do different.
 

Ian Grant

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Without going back and re visiting John Blakemore's and The Negative book, what does John do different.
It's not just John it's a British thing aiming it came from Minor White and Paul Caponigro although Caponigro got it badly wrong in his exhibition and book Monoliths. It's about Zone placements but I'm too engrained in how I've worked for 30+ years to remember the exact differences without going back to books myself.

Simplest explanation is in Peter Goldfield's Craftbool a PDF iof a photocopy is on Martin Reed's Darkside website.

Ian
 

Alan9940

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I, too, have conducted many film tests using a densitometer to measure for 0.1 over fb+f, but IMO a statement such as "shoot at 1/2 box speed" is very arbitrary. Not trying to start an argument...simply that my findings over all these years reveal different results. For example, since Ian brought up one of my favorite films--EFKE25--I rate this dead on at EI 25 for daylight shooting. Exposing this film at 1/2 box speed is not ideal and certainly won't lead to really good prints. Tri-X? I rate 400TX at EI 200, but Tri-X sheet film (320) at EI 320. Fomapan 100, Acros 100, and Delta 100 at EI 80. Ferrania P30 is box rated at ISO 80, but, for me, it's EI 32!
 
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