BTZS: Incident Readings in Flat Light

[sanking]

How did you calibrate the meter. If it is calibrated so that the lowest value in the negative that will print with detail is 3 stops below the indicated exposure then it will be a good exposure. If the meter is calibrated so that the lowest value in the negative that will print with detail is 5 stops below the indicated exposure, you will still get a printable negative but it will be more dense and some of you exposure latitude (for error in exposure/lens/shutter) is used up as the high portions get closer to the shoulder.

In typical BTZS practice the discrepancy between what the dome measures and what the dial does with the measurement is resolved as follows.

1. If you base exposure on the meter reading taken in bright light increase the exposure by 1 stop.
2. If you base exposure on the meter reading taken in the shadow areas decrease exposure by 1 stop.
3. Base exposure on an average of the shadow and bright light reading with no exposure compensation.

In my work I nearly always base exposure on a shadow reading, decreasing exposure by 1 stop. You can also just double the EI of your film and use the reading as is.

Sandy

[Ken Lee]

Thank you !!!

[Ken Lee]

Can anyone recommend an incident meter that is affordable, portable, well-suited to BTZS, and which handles a respectable range of EV ?

[Mark Barendt]

Don't know what you consider as a reasonable price but I use a Sekonic L-358 that works great or me, I've seen them used at around $200.

[Shen45]

I think mine is a Minolta 4F but any of the digital Sekonics are also excellent. Ken there are a few of us on this list who use BTZS as a complete system so if you are going to investigate the system and need initial help you will get sound advice. The Palm or the iphone is the way to go.

[Ken Lee]

I read and re-read the chapter on metering in the BTZS book. It addresses several of the issues we discussed.

[baachitraka]

In typical BTZS practice the discrepancy between what the dome measures and what the dial does with the measurement is resolved as follows.

1. If you base exposure on the meter reading taken in bright light increase the exposure by 1 stop.
2. If you base exposure on the meter reading taken in the shadow areas decrease exposure by 1 stop.
3. Base exposure on an average of the shadow and bright light reading with no exposure compensation.

In my work I nearly always base exposure on a shadow reading, decreasing exposure by 1 stop. You can also just double the EI of your film and use the reading as is.

Sandy

My question is, do modern incident meters suffer from this discrepency too. The meter I own shows the measured values in EV and with that by turning dial give me shutter speed and f-stop combinations.

[Kevin J. Kolosky]

I have not read the BTZS books, but I do recall light years ago when I attended Brooks Institute for a year that we learned a somewhat similar system for Black and white using an incident meter. It was called the Gamma system. Basically you measured a shadow and a highlight and determined a ratio, and then depending on that ratio you developed for a certain gamma which was figured out in advance by testing your film.

If I recall correctly (its been so long ago) gamma somewhat refers to contrast (slope?) on the straight line portion of the so called "curve", but I recall when I did my film testing that there weren't really any truly straight lines. There were curves, if ever so slight, and I often wondered why someone hadn't talked about using functions and derivatives to calculate slopes (instantaneous rates of change or contrast) on curved lines.

Regardless, I don't know that I would be so concerned what my light meter actually said, so long as I tested it and what it said was correct. By that I mean I don't care if the meter said I had to use ASA or ISO 800 for Tri X film using my methods and my equipment, so long as what it said gave me the proper exposure on my film and so long as the meter was linear, meaning that it reacted to light in the same way up and down the scale.

And if I recall correctly, it seemed like everyone in those classes used the good old Sekonic Studio Deluxe meter. No electronics. Cheap. Worked well.

[Michael Jones]

Can anyone recommend an incident meter that is affordable, portable, well-suited to BTZS, and which handles a respectable range of EV ?

Ken:

A Gossen digital luna pro is my incident meter. Small as a deck of cards. I think it works well; like Sandy, some of my images were used to illustrate Phil's book.

Go here for more incident metering info:

http://www.btzs.org/Articles/Sensito...20Part%205.pdf

Good luck.

Mike

[Ken Lee]

Thanks for replying to this old thread.

On Sandy's recommendation, I purchased a Sekonc L758, which provides both Incident and 1-degree Spot metering capability, and handles a broad range of lighting conditions. (I still have my Pentax 1-degree meter too: it's easier to operate in a pinch).

It took a while to study and test with BTZS, but I finally worked out a hybrid approach that combines elements of BTZS, Development by Inspection, and scanning.

Rose, 2012
Sinar P, 135m Carl Zeiss Jena Tessar
4x5 Ilford FP4, Procat HD