getting a personal EI without an enlarger or densimeter?

[Old-N-Feeble]

Most new photographers will under expose 1/2 of the images by statistical average. They wont be able to judge a correctly exposed negative on the light table unless any of you are present to coach the novice. Quantitive analysis of a negative can be obtained with a light meter in the absence of a densitometer.

Do you have any explanation why they might do this?

My guess regarding what ic-racer means is many people don't know to compensate for a scene with predominantly light or white areas.

 

[Bill Burk]

My guess regarding what ic-racer means is many people don't know to compensate for a scene with predominantly light or white areas.

I was guessing that as well, but thought that didn't account for half the photographs of a beginner. Without compensation, that would cause numerous shots to be ruined, but not half.

For what it's worth, I believe that a Matrix-Metered camera would most often suggest correct exposure at box speed, so that's what I set up my daughter with. For her, the rated box speed is the right speed.

 

[Xmas]

Do you have any explanation why they might do this?

Gaussian statistics or more simply tossing a coin heads over exposed tails under.

Pre 1961 there was a stop more margin in the ASA standard...

I cannot help having done a post grad course on stats sorry.

 

[RobC]

Is it because the white side isn't 100% reflective?


Steve.

No, its becasue 18% reflectance is not zone V. 18% is always 2 1/2 stops less than 100% ( or 90% which is only a small difference) and that is regardless of exactly how bright the lightest zone of the subject is. If the brightest part was on zone 20 then 18% reflectance would be on zone 17 1/2 or very close to it.

But your meter does stuff to the the reading it takes that no one ever talks about. i.e. it divides by the K Factor to get to the middle point exposure value based on where the manufacturer thinks the middle point should be. It may also do other stuff too but you'll never know becasue the manufacturers don't tell you exactly what they do, they just quote a K factor which is a correction factor applied to the reading, an offset from the reading if you like.

 

[pdeeh]

well, the brain (what all his friends call him) has decided to shoot some rolls at box, 2/3 box and half box develop based on the massive chart and the speeds listed for the times listed, gotta start somewhere, and just inspect the negs on a light box to see which looks best. he had a copy of image clarity so he's gonna shoot a blank fram to use as a base fog image and just do a simple comparison to see which has closest match as well as how the normal picts look.

i expect this to take some time. and it would not surprise me for the guy to shoot 10+ rolls for this experiment. but I'll admit, if and when he comes to his preference, I'll be trying out his results out of curiosity.

thanks again for your help guys. he has read the thread and also wants to say thanks. but he will not be posting as he admits if he gets into this "film thing" he could spend all day on this site.

john

Just to throw one more thing into the pot, and addressing the "no enlarger, no densitometer" issue, I'm slightly surprised no-one suggested this interesting approach by (the late) Barry Thornton: Dead Link Removed

It requires a darkroom, but is based solely around contact prints, which as we know requires minimal equipment.

I found it immensely useful

 

[Xmas]

The K % mentioned is the Kodak R-27 percentage and not everyone uses Tx or D76?
My grey card was not a Kodak one, a grey card only needs to have a flat spectral response, and for exposure you need to point it appropriately. I only used mine if bride had off white dress, after brainwashing a bridsmaid.
A Weston II or III galvanometer is calibrated for light values not exposure.
The Weston's zone calculator has a K transposition.
When you take an average reflected reading the K value is only valid for normal contrast scenes and Kodak suggest 2 stops more light for contrasty scenes, in film data sheets
An incident dome or panel K value ditto.
Any meter or simple camera is a light meter the exposure meter is 15 inches away from the light meter and you also need to cater for biased scenes like eg snow.
If you want to wet print adding two stops more exposure is a good idea anyway.

 

[Stephen Benskin]

If anyone is interested in exactly what the K-factor is, it is handled in great detail in (there was a url link here which no longer exists) Or you can download the whole Defining K "paper" used in the thread.

 

[craigclu]

Just to throw one more thing into the pot, and addressing the "no enlarger, no densitometer" issue, I'm slightly surprised no-one suggested this interesting approach by (the late) Barry Thornton: Dead Link Removed

It requires a darkroom, but is based solely around contact prints, which as we know requires minimal equipment.

I found it immensely useful

There is also an article regarding personal film speed on that site that was very enlightening for me back when he presented it (again, requiring a darkroom, but worthy of a read):

http://www.awh-imaging.co.uk/barrythornton/pfs.htm

 

[Stephen Benskin]

There is also an article regarding personal film speed on that site that was very enlightening for me back when he presented it (again, requiring a darkroom, but worthy of a read):

http://www.awh-imaging.co.uk/barrythornton/pfs.htm

That article by Thornton has some bad assumptions. Read it with care.

 

[pentaxuser]

That article by Thornton has some bad assumptions. Read it with care.

Stephen you might want to enlighten us about what those assumptions are. In my case in as relatively non technical terms as are commensurate with proper understanding.

I must admit that never having noticed from my experience the extent of over-developing that he believes is built into most developer tables this has always been one facet of Barry's articles that I wonder about.

Of course this may not be one of the "bad assumptions" to which you refer

Thanks

pentaxuser

 

[craigclu]

Here's a down and dirty system that I use... First of all, I am a nut job with 3 densitometers and have been back and forth with many trials, mostly out of curiosity and wanting to learn over the years. Still, I normally rely on the following and general experience.

I have mounted a Stouffer RZ9 Zone strip to a Kodak gray card edge. I can quickly see if there is separation at the extreme zones and make some reasonably accurate decisions on exposure/development times, etc from a quick look. I always do this on new films or developer combinations. When I have a spare frame and/or remember to, I include a frame on known materials and equipment to catch if anything is going amiss on metering, solution activity, etc. I can also do subsequent frames up/down in exposure to determine shifts.

I've attached the card/zone combo to illustrate. The large gray card area also gives me a readable area for checking on a densitometer so I find it a usable, consistent reference point. I can also plot projected curves from the smaller step wedge areas if I want to delve further. I find myself doing less of this as experience starts to allow a lot of interpretation from a simple inspection with a loupe on the film.

 

[Stephen Benskin]

Stephen you might want to enlighten us about what those assumptions are. In my case in as relatively non technical terms as are commensurate with proper understanding.

I must admit that never having noticed from my experience the extent of over-developing that he believes is built into most developer tables this has always been one facet of Barry's articles that I wonder about.

Of course this may not be one of the "bad assumptions" to which you refer

Thanks

pentaxuser

Thornton:
"Typically, standard ISO 400 emulsions work out at about 160, and 125 at 50 or 64 (I exclude T-Max from this). Skeptical readers are probably right now saying, "Oh yeah" So why do I say this? I mentioned earlier that exposure meters are set to read any scene as if it were 'average' or 'middle' grey: the standard 18% reflectance which manufacturers like Kodak reproduce in their commonly available grey card. I have a question. Who says that the average of a typical scene is 18% grey? Nobody I have asked has been able to tell me how this assumption arose. If it is incorrect, then we immediately have an error effectively in the nominal film speed. I believe the correct 'middle grey' should, in fact, be more like 9%. There is much confusion about this 'average' or 'middle' terminology as well. When asked, many of my clients say they visualise it as the exact mid-point between black and white; the reading given by a meter pointed at, say, a chessboard with an exactly equal number of equally sized black and white squares. In fact, such a scene would give a reading, theoretically, of exactly half the reflected light of a totally white board. Half the light means the same as one stop less or one zone less; so, if pure white is zone X, then the chess board would indicate zone 1X on the meter, not the stipulated zone V for middle grey. To get a zone V reading, the chessboard would have to have around 80% of its area black. Try it with a mock up and you will see this is so. But is this 18% right anyway? If the luminance range of a typical photographic scene is around seven stops - and a surprisingly large proportion do seem to be - then that is 2.1 in log terms. Half of this is 1.05, which translates to a reflectance value of around 9%."

This section is pretty much all questionable on some level. The ISO statement is dead wrong. ISO, middle gray, and Thornton's following point are covered in the Defining K document. In addition, from Jack Holm's paper Speed Relationships and Tone Reproduction,

"Scene Statistics
Two significant assumptions which are often neglected in exposure determination concern the scene range and mean 'reflectance. They are as follows:
That the luminance range of a statistically average scene is 160:1 (log range 2.2), and the resulting exposure range on the image capture medium is 80:1 (log range 1.9), corresponding to a camera flare factor of 2.

That the mean log luminance of a statistically average scene is approximately 0.95 log units below the highlight log luminance (edge of detail in white) and 1.25 log units above the shadow log luminance (edge of detail in black), and that this mean luminance is assumed to be the luminance metered, directly or indirectly, for exposure determination. These values result in the mean luminance correlating with a Lambertian scene reflectance of 12% for 100% highlight reflectance or 14% for 128% highlight reflectance. Values ranging from 10 to 18% have resulted from various experimental determinations. The 14% value is used throughout this discussion as it is assumed that the highlight reflectance in a statistically average scene will contain some specular elements. Flare results in the mean log exposure being halfway between the highlight and shadow log exposures."

Note: 12% is generally used in exposure models and is used with exposure meter calibration. Also note the part about flare.



Thornton:
"Nevertheless exposure meters are supposedly set to render anything they read as standard 18% grey, which is zone V in the zone system."

Exposure meters are not designed to render tones. They use luminance and the exposure calculator to determine the exposure settings necessary to produce a log-H of 8 lx / ISO at the film plane. A detail explanation is in Defining K. Here is an excerpt:



Thornton:
"For instance, have you ever checked your meter? I have two different spot meters, a Pentax and a Soligor. The Pentax reads 2/3 stop faster than the Soligor at low levels and 1/2 stop faster at high levels. My Weston and various camera meters all give different readings from the same subject under the same light, but vary differently at different light levels. Similarly, the llford digital thermometer I use is 1'C adrift from my Kodak mercury version. When all the other possible variables in taking and processing, such as shutter speeds, real lens light transmission compared to marked aperture, flare factors, lens extension, agitation technique etc, are taken into account it's not surprising that practice deviates from laboratory theory."

While materials and equipment are tested and calibrated under controlled conditions, these conditions are designed to reflect working conditions or to present an an average of those conditions. Allen Stimpson's paper, "An Interpretation of Current Exposure Meter Technology" has an excellent explanation of light source calibration and photo cell spectral sensitivity (available in the Defining K link). There will be variance but for most conditions it's not sufficient enough to affect quality. In many cases many of the elements Thornton lists can actually cancel out the affects of each other and they are part of the equation that calculates K.



Thornton:
"Theoretically it's possible that all the factors could pull in one direction to give a higher than nominal speed. But I have never come across it in hundreds of cases. It is also true that some film makers have stopped quoting rigid ISO speeds in favour of an EI (exposure index) figure. The basis for this isn't always clear, but Kodak's own publications state that a four stop subject brightness range for full detail in shadow and highlight is considered normal."

His use of the term "film speed" is incorrect. Most of the factors he has listed will influence exposure, not the effective film speed. The films that manufacturers have stopped quoting ISO speeds were T-Max P3200 and Delta 3200. This is for a different reason than Thornton is implying. Not sure what Kodak publication states a four stop subject "brightness range" (should be luminance range) is from, but if the quote exists than there's a question of what "full detail" defines. The statistical subject luminance range is 7 1/3 stops and this excludes accent black and specular highlights.

Thornton:
" In describing how to determine your true film speed, Kodak actually say that most people generally find they need a number slightly lower than the film's rated speed (Kodak Workshop Series, Advanced Black-and-White Photography)."

I haven't read this source but Thornton's use of the term "true film speed" is specious. What he should be using is exposure index (EI). The only true film speed is the film's ISO speed. If sensitometrically tested without following all of the ISO guidelines, the term effective film speed can also be used.

Thornton:
"Since each zone above zone 1 is achieved by doubling the exposure (i.e. increasing by one stop), we can move back down from the meter indicated exposure for zone V in the same way to reach the theoretically correct exposure to produce zone l for the claimed film speed. "

Problem is the ISO speed point is 3 1/3 stops from the metered exposure point and Zone I is 4 stops. The two systems are different and not comparable. Thornton's assumption that his testing method somehow determines the true film speed is erroneous. It is a way of determining Zone System EI. Something to keep in mind is that film speeds changed with the 1960 ASA standard, effectively almost doubling, but the Zone System testing method has not changed. Before 1960 the two systems would have shown a correlation, but not after.

The rest of the article appears to be basically a how to.

Mostly what I disagree most with is the insinuation that the scientists that design and manufacture film are wrong about it's use. I react the same way when some guy off the streets claims that evolution can't be true because it violates the second law of thermodynamics.

 

[RobC]

I don't need to know any of above to get an acuurate EI and dev. I just reproduce what adams did which was to photograph a piece of hardboard from zone 0 thru 10 and then print each neg with exact same print exposure and dev.

The resulting prints tell me if I have EI correct and if I have development correct for a zone 10 neg.

Its really easy peasy and doesn't require any maths or sensitometry or understanding of K factors or any other hocus pocus about flare or standards or how meters work or what their k factor is. And you actually learn something useful about printing and doing real world practical evaluation of your system.

The best thing about banging your head against a brick is wall is it's so nice when you stop.

 

[M Carter]

Here's a quick tip on saving film when shooting 35mm rolls for testing.

Cut several little pieces of blue painter's tape, maybe 1/8" x 1/2". Fold over about 1/3 along the strip and stick adhesive-to-adhesive so you have a sticky part and a "tab" to lift them.

Load your camera, set up a still life with repeatable light and a good range of shadow to highlight detail (I use styrofoam packing blocks for highlight detail), throw in a gray card or chart. Shoot 4 or 5 brackets and then advance the film to a blank frame. In the darkroom or a changing bag, open the camera back and stick a "tab" of tape on the blank frame (roughly center it on the back of the film aligned with the lens opening, doesn't need to be exact). Close the back and advance 1 frame.

Shoot the same set of brackets, and repeat. On a 24 roll, if you shoot a 4-stop bracket, you'll end up with 5 identical brackets, each separated by a blank frame, which is marked with a tab of tape.

Now, in the changing bag or darkroom, open the back, pull out the cartridge, and cut it away or canopener it and discard. Unspool the film from the takeup reel, and feel for the tape tabs as you pull the film off. Cut the film with scissors at each tab and discard the tape (in a bag, just stick 'em to the empty cartridge to be neat). You'll have 5 strips of film. Place 4 of these in an old 4x5 box or light-tight container, like a spare film tank. Thread one strip onto a reel (4 frames will hold just fine in a reel).

Process this strip, observe it, even print some 5x7's or 8x10's with a #2 or 2.5 filter. Process a 2nd strip, altering your time, dilution, whatever based on observing the first strip. Take notes and include the frame number range in your notes. In an afternoon, you can try 5 different processing scenarios on 1 24 frame roll of 35 with just one or two small batches of dev and 1 batch of fix. Just keep your dev. temp consistent unless you want to experiment with dev temp effects.

You can re-use even one-shot developers a couple times since the dev won't be exhausted by 4 frames.

This won't give you the range of images from shooting an entire roll, but I think it's a great start at figuring out how to get negs with the density range you desire for your style.

Kinda wondering if this would work with 120 film - I don't know if on, say, an RB67 you would screw things up by opening the back mid roll - would the back "think" you need to wind a bunch of paper to get to frame 1? Or maybe just remove the revolving adapter and stick tape on the emulsion side, at the edge, and not use the blank frame method, giving you 3 strips of 3 brackets? Hmm...

 

[pdeeh]

Without in any way belittling or trying to undermine your points Stephen, it is also interesting to note that even if Thornton was wildly incorrect in his theoretical understanding and statements, he nevertheless managed to produce beautiful prints.

 

[RobC]

Anyone here actually meet Thornton or attend his workshops?

 

[Xmas]

Anyone here actually meet Thornton or attend his workshops?

Not for a while

http://www.amateurphotographer.co.uk/forums/showthread.php?5089-Barry-Thornton-Has-Died

 

[MattKing]

Without in any way belittling or trying to undermine your points Stephen, it is also interesting to note that even if Thornton was wildly incorrect in his theoretical understanding and statements, he nevertheless managed to produce beautiful prints.

As does Bruce Barnbaum

 

[RobC]

Not for a while

http://www.amateurphotographer.co.uk/forums/showthread.php?5089-Barry-Thornton-Has-Died

Yes I know but did anyone ever meet him or attend his workshops back then.

 

[Stephen Benskin]

As does Bruce Barnbaum

Totally agree. Some of Barnbaum's ideas are out there.

 

[Bill Burk]

Without malice, I don't know any Zone System writeup which is free of errors.

I may need to pick up the White/Zakia/Lorenz New Zone System Manual though, because of any author... I think Zakia is the best scientist and he may have given us a solid reference.

 

[Xmas]

Correct. You don't have to be correct about what is actually going on in order to make great prints. Thornton is worse than Barnabum in some ways since his wrongness extended beyond sensitometry into developer formulation/photochemistry, whereas Barnbaum limits his wrongness to sensitometry.

Printing is where most of the control is, and the materials give us enough latitude throughout the end-to-end process that there are different ways of getting from point A to point B. You can easily be wrong about what kind of negatives you're making, how it all works etc., and make great prints. This is why most photographers who write books on technique should simply explain how they do it and stop there, rather than explaining how things work, and worse - why their techniques are correct and others are incorrect (Barnbaum does this).

All the bad technical information these guys have spread is the main reason people are obsessed with the concept of EI, and approach the whole exposure concept backwards, by starting with an assumption that the ISO speed of a film is somehow incorrect, or a marketing conspiracy, or a lab measurement which has no basis in reality, or something for amateurs but not for serious craftsmen. Since the person in question (re the original post in this thread) is at the beginning, my advice would still be to reverse the thinking, start out with an assumption that the ISO speed is the correct EI, and proceed from there.

No I'd disagree you only need to read Kodaks film data sheet.

 

[rbultman]

Without malice, I don't know any Zone System writeup which is free of errors.

This must be why I am so totally confused about determining personal EI. I have several texts including The Negative, The Zone VI Workshop, and Perfect Exposure by Hicks and Shultz (sp?). None read like an engineering test procedure.

If Barnbaum and Thornton are so utterly wrong, where is the procedure to be followed if one does not have a densitometer? Is the below any good or is it utterly wrong too?

http://www.normankoren.com/zonesystem.html

Regards,
Rob

Sent from my Nexus 5 using Tapatalk

 

[RobC]

Barnbaum used highly dilute HC110 which loses you at least 1 whole stop of useable film speed. Instead of him saying that meant he should use an EI of 200 for his 400 speed film, he says you should use zone 4 for shadows (using EI 400). Both will produce exactly the same exposure. What he should NOT have done is say Adams was wrong because he wasn't. Barnbaum is just not smart enough to realise why he needs to use zone 4 for shadows. He's not wrong becasue he hasn't used a lower EI. He's wrong becasue he says everyone else is wrong.

Thornton was a pedant who got a lot of things wrong and was prone to ranting at students attending his workshops. Impossible to take him seriously.

The B+W theory photographers who get elevated onto pedastals are those who write theory books. If they had never written a book on photographic theory you are unlikely to have ever heard of the vast majority of them.

AND

what makes you think ISO box speed isn't the correct EI for you? Until you find a good reason to devaite from it then don't. Or in other words, if it ain't broke don't try and fix it.

 

[MattKing]

Part of the problem with all of the people like Barnbaum is if you follow what he does, you to may end up with better negatives, even if your understanding becomes worse!

In contra-distinction with Steven Benskin here on APUG - whenever he posts, and I go through the effort of figuring out what he says, my understanding increases, even as my head starts to hurt.

I am, however, grateful for the pain.

EDIT: Correction - Stephen, not Steven