Studio exposure/development test for black and white film illuminated with strobes

[Peter De Smidt]

I've been concentrating lately on studio work with strobes. At first, I tried the old "just do it" method, but I wanted to get a little more systematic. I'm not an expert, but I've been exposing and developing film for a long time, and so hopefully I'm not too off base. If I am, please correct me!

We all know that exposure predominately effects the darker areas of the scene, whereas development mainly effects the brighter areas. In landscape photography, you can use a spot meter to place detailed shadows on Zone III, which should lead to bright areas falling on Zone VIII for a normal scene, and you use the exposure and development that'll give you the appropriate film densities for your intended use. If you have a non-normal scene, you adjust exposure and development to compensate. (You don't _have_ to have the bright areas fall on Zone VIII. You can adjust exposure and development to give the overall look that you're after. I regularly let the bright areas fall higher than Zone VIII. Many current films have a very straight line response to more exposure.)

If I had a spot meter that worked with flash, I'd be all set, as I could do the same thing I do for a landscape with a subject in the studio. But I don't have one. I only have incident flash meters.

So the procedure for landscapes with incident meters is to meter sun and shade to find the subject illumination range. You then set the meter to twice the film speed and take a shade reading. That's the exposure, and then you develop according what's indicated by your subject illumination range. (This incident stuff is all Phil Davis Beyond the Zone System.)(See Ken Lee's excellent "The Myth of the 18% Gray Card" at: http://www.kenleegallery.com/html/tech/index.php)

So in the studio, fill light = shade, and fill light + main light = sun, as the brightest parts of the image will receive light from both the fill light and the main light, whereas the shadowed areas will only receive light from the fill.

I did the following test. I set up two MacBeth Colorcheckers on a black flag. Between them, and perpendicular to to the first flag, I added another flag. I placed the main light on the right such that it'd only illuminate the right color checker. I placed the fill light right above the camera, such that it would light both color checkers. I entered twice the normal rating on the meter. For Acros, I knew that the real EI was at least 100, and so I entered 200 on the meter. I then adjusted the lights to give a two stop difference. In this case the fill side got f/5.6 and 1/2 and the other side read f/11.5. That's a standard "low contrast" ratio. I set the camera on f/5.6 and took a picture. I took three more picture, closing down 1/3 stop each.

For the next series, I upped the main light one stop. (3-stop difference.)

Finally, for the last series, I upped it one more. (4 stop difference.)

After I developed the film, I read it with a densitometer.

My EI in each case was 125. (The black square of the chart read at least 0.10 above film base plus fog.) I read the white square on the main light side to check high light density. In the future, I'll set exposure for flash in the studio by setting my meter at 250 and set exposure according to the level of the fill light, trying to remember to apply bellows extension correction if needed. There will be a different development time for each lighting ratio. Thus we're back to the "meter the shadows for exposure and develop for the highlights" maxim.

[ic-racer]

"We all know that exposure predominately effects the darker areas of the scene, "

Exposure change affects the mid areas the most. Toe and shoulder least.

[vinny]

Sounds overly complicated. While I've never seen anyone use that method of metering, if it works, it works.
Lighting with strobes becomes a lot easier with a dslr.

[Peter De Smidt]

It took me about 2 hours total to do the test, which includes driving to the studio, developing the film... That isn't much longer than a standard Zone System test. I now know the film speeds and development times for 4 different ratios, the most common ones I'll use, and I can extrapolate to others if needed.

[Taija71A]

Agreed with Vinny.

I too, am happy that this particular Methodology worked for you (at this time). :)
But, it most certainly is not what *I* would call an 'empirical' method.
--
Peter, what now happens on an actual 'Shoot'...
When your Subject Brightness Range is different than that of the Macbeth ColorChecker?

Perhaps, this is now... 'Food for further Thought?'

Best regards, -Tim.

[Peter De Smidt]

I have spent a couple weeks doing actual "shoots". I want'd to get more predictable results with varying lighting setups then given by the "try something and see" approach, just as one does with zone system testing for landscapes. In addition, I've been scanning the results of these shoots, and I'm investigating what negative density range produces the best results with my Cezanne. To do that it helps to be able produce specific densities....

I only used the Macbeth ColorCheckers because, first, they were sitting right in the drawer. Second, they have a nice matte black patch and matte white patch. I only used the black patch on the chart illuminated on by the fill light and the white patch illuminated by both lights. Any matte black or white would've been fine.

I have info now for a number of SBRs. So what's the problem again?

[Taija71A]

>> I then adjusted the lights to give a two stop difference. In this case the fill side got f/5.6 and 1/2 and the other side read f/11.5. That's a standard "low contrast" ratio. I set the camera on f/5.6 and took a picture. I took three more picture, closing down 1/3 stop each.

>> For the next series, I upped the main light one stop. (3-stop difference.)
>> Finally, for the last series, I upped it one more. (4 stop difference.)

Peter, as per above... You have now only changed your 'Lighting Ratios'.
--
Therefore, let's proceed with this 'thought' experiment further -- Okay?

Pretend, that instead of photographed the ColorCheckers...
You are now photographing 'say' two (2) Black Cats sitting 'side by side' on separate pieces of Black Velvet -- Each illuminated by their own 'lit' white candles (as per above).

What would your results be?

Why did your results change? Did your 'Lighting Ratios' change? (No).
You have simply... Just proceeded with your testing once again -- As per above.

Therefore what has now changed? Your Subject Brightness Range has now changed!
(*Reflective Flash Meter readings... Would of course indicate this).

[Peter De Smidt]

On one side, we'd have, in effect, a black cat in shade. On the other side we'd have a black cat in sun.
The sbr depends on the subject, and also on the illumination.
As far as I can tell, you don't like incident metering. That's fine, but it's what I'm going to use.

[mdarnton]

What I don't understand here is if you change your lighting ratios, and then change the development to bring them back to "normal", hasn't the modified development essentially unchanged the lighting ratios and you're back where you started, except with possibly damaged local contrast because of less overall development?

I'm not a big zone system fan anyway--the guy I worked for in high school had a string on his key light and one on his fill. That's how he set both the exposure and the ratios. I do the same thing now, but without the string. :-)

[Taija71A]

If I had a spot meter that worked with flash, I'd be all set, as I could do the same thing I do for a landscape with a subject in the studio. But I don't have one. I only have incident flash meters.

No problem. An 'Incident' Flash Meter is just fine Peter!
There is definitely no need to acquire a different Light Meter.



As far as I can tell, you don't like incident metering.

I can 'happily' work with either a Flash Meter in 'Incident Mode' or 'Reflective Mode'.
I have no real preference...
--
As long as you understand 'Lighting and Metering'... Nobody really cares how you choose to Meter -- Do they? All that really matters is:

1). That your Light Meter is 'Accurate and Consistent'.

2). That you are aware of the 'inherit' limitations in using an Incident Light Meter.
(*Whether this be with Ambient and/or Electronic Flash)

3). That you know how to interpret the results.

and of course...

4). The final RESULTS!!!

Have Fun! :)

[Peter De Smidt]

I came across Phil Davis's suggestions:

"Here's a summary of the procedure:

• Meter the highlight area (pop the flash to get the reading)
• Meter the shadow area
• Subtract the low reading from the high (in stops) and add 5; that's the SBR
• Consult your EFS/SBR chart to find the DOUBLED film speed
• Set this DOUBLED film speed into the meter
• Re-read the shadow area using this new DOUBLED speed
• Use the recommended aperture and shoot
• Consult the Dev/SBR chart to find the developing time." -Posted on the BTZS forum.

[DrTang]

and to think

me all these years just putting the flash meter on the persons face and pointing it at the camera lens

[bob carnie]

I always metered for the fill light by pointing at it . I would consider this my base exposure for most situations

I then metered for the main light - for 1:1 , 1:2 , 1:3 I would process normal, for 1:4 , and more lighting ratio I would consider drop process.

In all cases I was using a flash meter pointing the meter at the light .
I use the same principle for hot lights (which I prefer over strobes) but I am shooting small objects... Bellows factor seems to be more of an issue for me when its really racked out then I steamboat on base calculations.

[Peter De Smidt]

If you're going to shoot one way, with one light setup, same film, same development, a viable way to work btw., then taking one reading, or using a string, putting an x on the floor,...., should all work fine. But if you are going to change the lighting dramatically for each subject, it's useful to know what the shadow and highlight densities will be, especially if you're targeting a specific density range for you output process. That's all I'm after. Lot's of people don't want to work that way, and that's fine, just as only some people find the Zone System useful in the field.

If someone has a simpler or better way to achieve specific highlight and shadow densities under varying conditions with studio strobes, then I'm all ears.

[Peter De Smidt]

Bob, thanks for sharing your experience. I'm glad to hear that metering for the shadows works.

[SergeiR]

i point meter at lights.. ;) And develop same way, without much thought.. ;)

[Peter De Smidt]

Well, Sergei, that works pretty well in your case!

[cowanw]

The only additional issue That I have experienced is the choice of lens; the range of which, that I have, really do require different development times as well as different contrast ratios.

[ic-racer]

Printing with multigrade paper can simplify things.

[Peter De Smidt]

Bill, I agree. The type of lens, e.g. coated, non-coated, soft focus.....really does impact contrast.

[SergeiR]

Well, Sergei, that works pretty well in your case!

IMHO : one of best investments photographer can make is Dean Collins tapes on light ;) Strobes or not..

[Taija71A]

IMHO : one of best investments photographer can make is Dean Collins tapes on light ;) Strobes or not..

+1. Agreed in full 110% .

1). Exposure.
2). Shadow Edge Transfer.
3). Specular Edge Transfer.
4). Contrast between Shadow & Diffused.
5). Contrast between Diffused & Specular.

Dean Collins really knew what he was doing! :D
IMHO... There is no one else like him teaching (even) today.



I came across Phil Davis's suggestions:

"Here's a summary of the procedure:

• Meter the highlight area (pop the flash to get the reading)
• Meter the shadow area
• Subtract the low reading from the high (in stops) and add 5; that's the SBR
• Consult your EFS/SBR chart to find the DOUBLED film speed
• Set this DOUBLED film speed into the meter
• Re-read the shadow area using this new DOUBLED speed
• Use the recommended aperture and shoot
• Consult the Dev/SBR chart to find the developing time." -Posted on the BTZS forum.

Peter, do you happen to have the URL Link for this information?
I see a *potential* problem with this 'Methodology'.

But, before commenting further... I of course would like to read up on it in further detail -- Since this is just a 'Summary' of the information. Thank-you!

Best regards, -Tim.

[Peter De Smidt]

Tim,

I'm not sure if this link will work, but it was: http://www.btzs.org/Forums/forum/Default.asp?app=100&df=100&exp=0&forumid=7&fr=201&kw=&main=/Forums/forum/Default.asp&select=495#xx495xx

The book to check would be Beyond the Zone System, 4th Edition. I checked today, but our library didn't have a copy.

[Taija71A]

Got it. Thanks Peter! :)
Yes, I now see the 'specific' post from Phil... That you were referencing.
--
Just FYI... It is this 'Statement' (by Phil) that I see a *potential* flaw with:


>> Subtract the low reading from the high (in stops) and add 5; that's the SBR.


I of course have no problem with the first part of the statement (Subtract the low reading from the high (in stops) )...

... But, the 'add 5' does look suspicious?

I will now look further at the complete BTZS 'Thread' and get back to you -- Okay?
Thank-you!

Best regards, -Tim.

[Taija71A]

Previously, you cited the following (*Which I of course 'Wholeheartedly' agree with): :)

>> The SBR depends on the subject, and also on the illumination.

Therefore, our 'illumination' (Electronic Flash in this instance) is of course...
The difference between the Highlight Area and Shadow Area (Incident Reading).

However... How does 'Phil' know that our 'Subject Contrast' is always 5 f-stops (hence the 'add 5') difference?

For all we know... Our 'Subject Contrast' could only be 2 or 3 f-stops.
Then again... It could possibly be even more than 5 f-stops difference.
(*You get the idea of course!)

Perhaps, this calculation is 'compensated for' and/or adjusted... Somewhere else in his Plotter Program? Then again, perhaps I am missing something here?

I sincerely hope, that this all makes a little bit of sense! ;)

Best regards, -Tim.

[Kevin J. Kolosky]

Get yourself a good copy of the Kodak Professional Photoguide that has the gray scale in it.
Get a good incident light meter.
Get a good fixed fill light.
Figure out what light ratios you want to use.
Test.
Shoot.