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Photo Forum / Film Photography / 35 mm / June 2005Film speeds on OM10?
I'm new to photography and am learning on an old Olympus OM10. One thing I haven't been able to find out is what the unmarked settings on the film speed dial actually are. Does anyone know? I.e.: the numbers go: 25 . . 50 . . 100 . . 200 . . 400 . . 800 . . 1600 If I turn the dial to the second dot after 200, what is the actual film speed set to? 300? 360? I'm reading a book by John Garrett in which he pushes HP5 from 400 to 600. I like his results, and think I could use the extra speed myself when shooting indoors. But does the OM10 even have a 600 setting?! > I'm new to photography and am learning on an old Olympus OM10. One > thing I haven't been able to find out is what the unmarked settings on > the film speed dial actually are. Does anyone know? > > I.e.: the numbers go: 25 . . 50 . . 100 . . 200 . . 400 . . 800 . . > 1600 The dots will be third stops. The progression goes: 25, 32, 40, 50, 64, 80, 100, 125, 160, 200, 250, 320, 400, 500, 640 800, 1000, 1250, 1600. > If I turn the dial to the second dot after 200, what is the actual film > speed set to? 300? 360? 320 > I'm reading a book by John Garrett in which he pushes HP5 from 400 to > 600. I like his results, and think I could use the extra speed myself > when shooting indoors. But does the OM10 even have a 600 setting?! Pushing black and white film (extending development to increase contast) does not actually have much effect on film speed. It can seem that way because underexposures tend to be on the low-contrast toe of the film curve, and increasing contrast compensates for this. This works best when the scene is low in contrast to begin with. This is often the case with overhead fluorescent lighting typical of schools and offices, but is not usually the case with domestic lighting which tends to be contrasty to begin with. A 2/3 stop push (which is what you were talking about ie: 400 film exposed at 640) is not very much and may work fine even with higher-contrast domestic lighting. Normal development of HP5+ in Ilford Microphen can give an actual speed increase of about 1/3 of a stop or so over the same film in D-76 without increased contrast. That being said a modest "push" of HP5+ in Microphen to 800 often works very well. You might want to investigate the Ilford Delta 3200 and Kodak T-Max 3200 films for available light work. They both work very well at an EI of 1600 developed in Microphen. Yes. In the book all his HP5+ is developed in Microphen. The author says that it gives a 50% increse in film speed with no change in contrast. I think I'll put a roll through at 640 and see how it goes. Do you have any recommendations for how long I should develop in D-76? A guide I read a while back says normal time + .25 for one stop and + .5 for two? > Yes. In the book all his HP5+ is developed in Microphen. The author > says that it gives a 50% increse in film speed with no change in > contrast. This means that he is not "pushing" the film at all in the usual sense of the term. > I think I'll put a roll through at 640 and see how it goes. Do you have > any recommendations for how long I should develop in D-76? A guide I > read a while back says normal time + .25 for one stop and + .5 for two? I'd give either the same development as normal or possibly a little extra, but I'm not clear on what you plan to accomplish. Film speeds are based on the minimum exposure necessary to get prints rated as "excellent." With many B&W films (including HP5+) you can underexpose by two stops and still get "acceptable" prints. Note that the speed rating is based on the minimum exposure needed: there is very rarely any harm done by using a stop or two over this minimum provided that you don't combine overexposure and overdevelopment. The primary purpose of extending development is to make underexposures easier to print. If you underexposed two stops and developed normally, you would get rather wispy looking negatives which would require a #4 or #5 paper or filter to print. Both the low density of the negative and the high printing contrast tend to make the tiniest bit of dust show up very clearly. By extending developing times, you can get a more robust negative which prints on #2 or #3 paper. The usual recipe for success is to expose generously and develop moderately. Peter.  Signaturepirwin@ktb.net On 26 Jun 2005 in rec.photo.equipment.35mm, wrote: > I'm new to photography and am learning on an old Olympus OM10. One > thing I haven't been able to find out is what the unmarked settings [quoted text clipped - 9 lines] > 600. I like his results, and think I could use the extra speed myself > when shooting indoors. But does the OM10 even have a 600 setting?! Notice how the series goes: 25; 50 = 25*2; 100 = 25*2*2 (=25*2^2); 200 = 25*2*2*2 (=25*2^3);... So it's an exponential series. The 1/3 stops would be 2^1/3 and 2^2/3 of he base value. 2^1/3 = 1.25992104989487; 2^2/3 = 1.5874010519682. So the 1/3 stops above 100 would be 126 and 159. If your calculator won't do powers, the linear values 1 1/3 and 1 2/3 (1.333... and 1.666...) will be close enough. SignatureJoe Makowiec http://makowiec.org/ Email: http://makowiec.org/contact/?Joe > I'm new to photography and am learning on an old > Olympus OM10. One thing I haven't been able to find out > is what the unmarked settings on the film speed dial actually > are. Does anyone know? > I.e.: the numbers go: 25 . . 50 . . 100 . . 200 . . 400 . . > 800 . . 1600 [quoted text clipped - 5 lines] > HP5 from 400 to 600. I like his results, and think I could > use the extra speed myself when shooting indoors. But does > the OM10 even have a 600 setting?! If there are two dots between each of the 'doubling' intervals, then they are each one third stop changes, which is pretty much a standard. So this would give a progression that, after rounding, is usually expressed as: 3 4 5 6 8 10 12 16 20 25 32 40 50 64 80 100 125 160 200 250 320 400 500 640 800 1000 1250 1600 2000 2500 3200 Etc. The 640 mark - one dot short of your marked 800 - should be close enough to 600 for your suggested use with HP5 that it'll make no difference. Peter > I'm new to photography and am learning on an old Olympus OM10. One > thing I haven't been able to find out is what the unmarked settings on [quoted text clipped - 9 lines] > 600. I like his results, and think I could use the extra speed myself > when shooting indoors. But does the OM10 even have a 600 setting?! Lookk on the web for a manual. But it appears that the dots represent 1/3 stops of film speeds. eg: 50 [64] [80] 100 [125] [160] 200 600? No; 400 [500] [640] 800 Cheers, Alan. Signature-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. |
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