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Pete's answer is perfect. For better clarity, regarding the last suggestion, I should say "you must use 91.3 grams of metabisulphite as substitute for 100 grams of bisulfite". Franco Rallo

Dear Martin, I bougt in Rome, second hand, two Mentor large format cameras about three years ago. One is called Mentor Studio, 13x18 cm; the other is called Mentor Panorama, 18x24 cm. Mentor...

Some more words about my suggestion, regarding a possible side-effect. The developing solution reacts with the oxygen, and this could cause the internal tray to reach a pressure lower than the...

Sean's idea can be perfectioned using one more larger tray, flat bottom, containing about half an inch of water, in which you can place the two-trays assembly suggested by Sean. In this way, the...

Hi Jacque - I don't know that particular convertible, but I think one can apply the general rule about composite lens: 1/F = 1/F' + 1/F" where F is the total focal lengt, and F' and F" are the...

Dear friends, in my previous answer I typed wrongly a number in the first numerical example. I wrote: "... you set the aperture ring at 19 mm and this will correspond to normal aperture f/22." The...

Dear Cheng Lu, I have and use the same lens; the way to calculate the "normal" aperture values is very simple, if you follow this procedure: 1) With the lens combination you prefere mounted on the...

Hi David, I will try to answer to your question(s), starting from the last one. I don't think your Goerz lens is radioactive, because from what you say it shold be quite old and at the time of the...

Hi Robert; your question seems rather simple, but in effect it involves quite a lot of complication. Generally speaking, focusing exactly with a wide aperture is easier, because the depth of focus...

Assuming that a lens with such a name should work perfectly with the two elements together (so at least the first 100 $ are well spent), I agree completely with Sean Yates, expecially for the...

David, as the world is full of magicians, my books suggest another magic number, i.e. k = 0.036 So the "perfect" diameter comes out to be O.62 mm. And the coresponding f value is f/483 about 10...

Hi David - Lenses of focal lenght from 100 to 110 mm are normally used on 6x9 cm format cameras; a good rule for enlarging is to mount on the enlarger the same focal lens of the camera used for...

I would like to use lith negative film in old field cameras of various sizes (9x 12, 13x18 and 18x24 cm) because lith foils can be easily cutted to the size and placed in the film-holder leaving on...

Dear Ron and David, thank for your answer. I wrote more on your e-mail address. Franco.

I have a couple of very old 9x12 cm folding plate cameras (about 50 years old) w ith good shutters, excellent lenses (Zeiss Tessar) and broken diaphragm blades. It is reasonable to sobstitute the...

Dear Kevin, your camera should be a 9x12 cm plate camera (around 1914) made by one of the four Firms which merged to form Zeiss Ikon in 1926. ICA was at that time the major producer of cameras in...

In mine opinion the main advantage of removing the front lens is that in this way the diaphragm stays before the lens, so the light travel is: subject-diaphragm-lens-film. It seems that this...