BTZS expodev question

[swmcl]

Hi,

Can someone tell me what the hi-zone variable in the Expodev / Metering / Zone section is please ?

Under the Zone system tab, there are 4 variables. Lo-EV, Hi-EV, Lo-Zone and Hi-Zone.

I sample my scene, I put in the lo and hi EV readings, I understand the Lo-Zone should be where I wish to place the Lo-Ev reading but what of the Hi-Zone ?

I need to understand what the Hi-Zone variable is doing ...

The other issue is that it won't go beyond 10.0

Cheers,

Steve

[limnidytis]

If you are metering by the zone system, the lo/hi EV values are what you read with your spot meter. The zone values are the zones where you want to place the readings. I assume you know the program requires raw data from a film test to use as a basis for calculations.

[swmcl]

Thanks for the reply.

Yes I have a fully tested film and developer combination in place. The zone values are what zones ? On the paper ? Why would I put in zones when I've already put in the EV values between which I have decided is the information I wish to record ?? It is fairly obvious to me (and to no-one else !) that my high EV value is the 'very nearly white' point on the paper and the low EV reading is the 'very nearly black' point on the paper ... I just don't get the zonal information being asked for ... and it isn't trivial because the resulting calculations affects the SBR and recommended exposure that the software comes up with ...

The limit of 10 Zones ? We all know the film records more than 10 zones so this must be a paper zones spread ... ??

The user manual is almost none existent. As the original author has passed perhaps those who are continuing the software actually don't know the product as well as they might ?? The user manual is almost a cynical joke in my view.

Frustrated.

[ic-racer]

For example, the HIGH value does not have to be your "very nearly white" value. One can choose to use the next values lower because maybe the "very nearly white" value is difficult to meter or not existing in the scene. So if you use zone VI for that high value you enter zone six with its corresponding EV value.

Unless you are including light sources in your scene, many scenes, when projected on the film plane, will max out below 10 zones.

BTZS is not perfect. I don't use it, but it has many supporters and it works as well as any other exposure/development system when you get it figured out.

[swmcl]

Thanks ic,

I do trust your judgement. Ya just gotta understand I feel a bit left out in the cold ... especially with the user manual.

For everyday normal printing to the fullest scale possible would it not be always the case where you'd leave the hi-zone and lo-zone alone altogether ? Say set them to 1 and 9 and forget it ?

Thanks for your reply too BTW.

[chris_4622]

The SBR won't always fit the scenario you mention, leaving the hi/low zone set to 1 and 9, so you have to decide where you want to place the corresponding EV. For example a scene where the EV range is 7 to 12 you can put the 5 stops in your choice of zones; 2 to 7, 3 to 8 etc. you can also expand or contract the zone range within the limits of the film. The zone range in the app is for printing reference.
Hope this helps.

[swmcl]

Thanks Chris,

So if I measure a scene and its range is say 7 stops or EV then I put the same range in the zone settings say centred around 5 so for a 7 stop range it would be 1.5 and 8.5 ... ?

I'm thinking it would be a range floating in the centre rather than anchored to one end or another ...

This is getting better for the asking, thanks all.

This means of course that the 10 zone range I was referring to earlier is an SBR limit then ... hmmm

The developer test that I have done is such that the dev doesn't like the pulling of film. It isn't a go-slow developer so the CI figures are quite steep from a small dev time. If I wanted to get more of a range of the scene into the print I'd need a flatter curve and less aggressive developer. That or I'd need to start again with stand development or a two bath developer.

I wonder if the Expodev is going to fall over with the idea of stand development ...

I'm learning heaps but I'm also burning film on dumb testing ... :-)

I feel that I will be far more able to produce a really effective negative though. My confidence is rising slowly ... LF and sheet film is a significant science as well as an art. I'm not one for hoping all will be well when I shoot. I wonder if you can tell that :-(

Cheers,

Steve

[limnidytis]

It helped me to read the BTZS book 4-5 times, and make notes. Reading some of the old DMax newsletters helped, too as there are several that focus on film testing. You can buy copies of the news letters from the View Camera Store.
It may not be explicitly stated, but the system is designed to give a N time of about 8 minutes, so you have curves above and below the 8 min curve to allow for +/- calculations. When initially testing, you can just test the 8 min time. The curve should have a gradient of about 0.5, which is considered N in BTZS. If the curve is far off from 0.5, you should change you developer dilution to adjust the curve to 0.5 at 8 min, then complete the film test with the other times. I would doubt you could get the system to work with stand development. I find expodev to be handy - it automates all of the binary math calculations.

[swmcl]

Hi limnidytis,

I've got the book and as far as I can see there is no reference to the Lo Zone nor Hi zone - the Phil Davis book that is ...

The default is 3 and 7 as I recall. I can see that changing them does change at least the development time for the film so I need to know what they do. I believe they are paper limits but I don't know much more than that. For example, can they be expanded to say 1 and 9 ? If they are there as a print tonality control which will require a more intimate knowledge of the paper characteristic then that's fine but what do others do? DO they just stay within a 4 value range and move that around - say go from 2 to 6 instead of 3 to 7 ?

I'll try to find some more papers like the DMax stuff you mention too.

Rgds,

[Bill Burk]

Hi swmcl,

In classic Zone System metering, you can take any two meter readings and place them on any two Zones of your choice (but you cannot make them crossover).

So a typical normal scenario you can read a shadow, place it on Zone II... then read the palm of your hand and place it on Zone VI. That's enough information to determine exposure and development...

Here is an example of that. This places Low EV on Zone II and Hi EV on Zone VI:

Low EV = 5
Low Zone = 2

Hi EV = 9
Hi Zone = 6

If you plug those numbers in, I think you will get a normal "N" development time.

This may help confirm that's the right way to do Zone System placement: This should give exactly the same recommended exposure and development time as the first example:

Hi EV = 8
Hi Zone = 5

Hi EV = 10
Hi Zone = 7

And if you want to make your hand look brighter in the print, you can input this and you should expect "N+1" as a result.

Hi EV = 9
Hi Zone = 7