Bronica macro bellows
I wondered if an APUGer might be able to give me some advice:
A few months ago I bought a macro bellows for my Bronica-SQB. I've used it a couple of times to test it out, and on both occasions got good results by my un-researched technique of spot metering the the subject directly and the ground glass, then averaging the EV result. Does anyone have some tips for more "sure fire" exposure results? I haven't used it (the bellows) for anything critical yet, but would like to soon.
The same considerations affecting bellows extension that apply to view cameras would also apply to your macro bellows. There are several different methods of calculating exposure compensations.
One is to measure the relative size of the actual object as compared to the size of the image on the focusing screen.
Another is to measure the amount of bellows extension and adding that to the amount of lens nodal point to film plane dimension when only the lens is used. For instance if you are using a 105 mm lens (this for sake of conversation would be four inches) if you add four inches of bellows extension to the exposure (this would increase the first dimension by four and a total of 8 inches). In computing this you would convert the inches to Fstops so you have effectively increased it from F4 to F8 or a factor of two stops. So the proper exposure would be two stops more then your spot meter indicates. I personally would not rely on averages of meter readings. I would spot meter the low values and base my exposure on that.
If you have a metered prism on your Sq then the metered prism should automatically adjust the exposure for you.
Hope that this helps. Good luck.
Sure fire? Bracket?
I'm not sure how well that would work with a MF camera.
Measure the extension you're using and compare it with what the lens needs at infinity.
TTL in camera meter is the simplest.
Thanks for the advice, I'll try out your suggestion. I may also post a scan of one of the negatives I have already made. I used Fuji Acros souped in Rodinal 1+50, and got good results.
I should also point out that the SQ-B doesn't have the needed metering gubbins so the TTL metered prism wouldn't work. I'm not too keen on buying that much more equipment for my Bronica at the moment as I'm planning to go 8x10 next year. One item I'm thinking about though is the 250mm PS lens, although I would not be adverse to the 'P' series lenses depending on the performance.