I read in an article by Phil Davis that many who follow the techniques proposed by BTZS prefer to use an incident meter, rather than a spot meter. Why? What is the technique used to differentiat highlight and shadow?
I read in an article by Phil Davis that many who follow the techniques proposed by BTZS prefer to use an incident meter, rather than a spot meter. Why? What is the technique used to differentiat highlight and shadow?
With BTZS procedure two incident meter readings are taken, one in the shadows, the other in the highlights. This difference between the two is then added to 5 (which is the number of stops in a flat one-dimensional scene with no shadows) to give what is called the SBR, or subject brightness range. SBR 7 is considered a normal
contrast. SBR 5 is a very flat scene, and SBR 15 would be a very high contrast scene.
Exposure could based on either the shadow readings or on an average of shadow and highlight reading. The SBR value determines development time.
Sandy King
This is the technique that Mr. Davis found that works best for him. It's not necessarily any better, or worse, than any other technique. Like all techniques, some people will swear by it, and some people will swear at it.
I personally find the use of a one degree spot meter to be highly intuitive. It works really well for me, letting me hit my exposures spot on, even when the shadow detail I'm trying to hit is the shadow detail on a rock in the middle of a fast flowing stream.
So I'm not tempted by the BTZS technique. That's just me, it doesn't mean you should or shouldn't be tempted because as we all know, YMMV.
Bruce Watson
Objects of varying colors reflect light in varying proportions to the light striking it. Phil preferred to meter based upon the light striking the object rather than being concerned with the varying reflectance due to an object's color.
While Sandy's explanation is succinct, a one or two paragraph primer of a hundred plus page concept of metering and development is not going to be completely helpful or accurate. I suggest you review the book at a bookstore to get a feel for how Phil's concepts work.
Good luck.
Mike
You may wish to visit:
http://btzs.org/
For more information.
Don Bryant
Most people who have used both Zone system and BTZS would agree that BTZS has better testing procedures. Better in that compared to Zone testing, BTZS takes less time, uses less film, and gives more precise results.
Also, while I gave a concise answer to the question of the OP, BTZS is not tied to incident metering. The Winplotter program, which Phil Davis developed originally for use on MAC+ computers, produces data for both incident and reflective reading, i.e. it gives both SBR values and N values. Davis discusses in his book the advantages and disadvantages of each type of metering system in his book.
These days, and especially in LF, many (perhaps most) people are exposing and developing to scan and print digitally rather than print directly with silver papers. In that case the precision of both Zone and BTZS is not required as one can simply expose for the shadows with one single incident reading, and develop to a fairly low CI.
Sandy King
I have used spot meters for years and dabbled with various forms of zone system controls. Then I migrated to BTZS with spot metering. I do my own testing and use the WinPlotter and ExpoDev software. Certainly not for everybody but has been great for me.
Lately, I have been trying the incident metering method. I have not done it enough to be a convert yet and need to print more of the negatives to see what I think. But, it is significantly quicker and I think easier. I have a Luna Pro SBC meter for incident readings and the needle system which shows relative difference between readings in stops is much more intuitive and mentally quicker than using absolute EV values from the spot meter. So give it a try and see what you think. I am almost a convert to the incident metering.
I use a hybrid of the two systems. An incident meter to find the SBR and a spot meter to measure and place my exposure. Works for me anyway. I guess I must be one of the few left actually printing on silver. Not because it's better (it's not) but because I enjoy it.
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Eric Rose
www.ericrose.com
I don't play the piano, I don't have a beard and I listen to AC/DC in the darkroom. I have no hope as a photographer.
That was Phil's personal preference. I'm not sure it's the preference of a lot of users. I knew three or four peole who used the BTZS system and none of us used an incident meter. I attended two of Phil's workshops and I'd guess that about 75% of the people there were using reflected light meters. The system will work fine either way so to me it's just a matter of personal preference. Reflected light meters seem more familiar to a lot of people because that's what the meters in 35mm cameras are.
Brian Ellis
Before you criticize someone, walk a mile in their shoes. That way when you do criticize them you'll be
a mile away and you'll have their shoes.
Bruce - It sounds like you perhaps don't understand the "BTZS technique." It's as usable with a spot meter as with an incident meter. Phil Davis happened to prefer an incident meter but you could use the system with your spot meter equally well if you were so inclined.
Brian Ellis
Before you criticize someone, walk a mile in their shoes. That way when you do criticize them you'll be
a mile away and you'll have their shoes.
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