20x24" negative MM size

i am in the intersting, challengly process of making a new 20x24" camera.
all the theory has been adapted into a working model of the set up.

next step is to make a carrier for the negative/glass plate.

i need the actual size of a 20"x24" negative in millimeters please.
it appeares that a 4x5 negative is slightly smaller than the exact convertion to mm.
it actually measures 100x125 mm, that means that 1" = 25 mm in filmsizes.
(the official conv. is 1"= 25,4mm)
will that be the case in 20x24" neg.??

needless to say, but i am looking for a useable lens for the beast,
allthough it seems that the front element of a 300 mm symmar will fill the groundglass in full,
even near portrait distance. but practice will show.
anyone with practical experience here?

klaus
denmark

I don't think there ever was an ANSI standard for that size. Maybe ask Ilford (or whoever is going to supply your film) how big they cut it.

thanks ice racer,
i am in contact with a Chinese company who can cut x-ray into any size.
i thought it would be of interest to others with a filmholder for 20x24.
i do not yet have the prices, all depends on how many i order of course, but it is a small company with few employies, i think they are quite flexible in the production.
the dont have b&w film, sorry.
i will order 50x60 cm that is european standard.
klaus

Hello I will use my first 20x24 ilford HP5 sheet film on saturday. I will so be abble to tell you what is the exact size this Week End if you still want to know.
X-ray film could interest me depending on the price, but of course with the right size...
Thierry M.L.

A 300mm symmar won't cover this format and would also be a very wide field of view.