Karl I don't know about that. When I worked in a camera store in College we had a shutter speed tester we used to test all used cameras and customer cameras in for service. I never saw any that where crazy like that. and I have never seen any of my copal's be off by more then some insignificant amount and its usually at the long range that they are off. My F5 electric shutter actually has a monitor in the camera that adjust it as it ages. I know that shutter is/was because when I bought it I ran it on a tester. All the way to 1/8000th. I think was off by some 10,000th. My f3 last time it was tested was pretty much dead on as well. Most REAL camera shops and for sure you repair shop will have a tester and you can buy them online ebay for $100 bucks but I don't know how accurate they are but they can go to 1/9999 from what I just found. What I do know is that a lot of older testers only go to 1/1000th or 1/2000th.
I'm sure on that old leaf lens is way out but I would have to see test that showed the crap result for more then 1/3 stop failure on any shutter in a respectable camera. Here are test done with a copal
The timing test of a Copal #1 by Jean-David Beyer shows that mechanical shutters are very accurate:
Indicated Correct 1 2 3 4 5 6 7 Average 1 1 0.92522 0.92269 0.92419 0.92401 0.92558 0.92678 0.92518 0.924807 1/2 1/2 0.50192 0.50174 0.49964 0.50206 0.50244 0.50041 0.50054 0.501250 1/4 1/4 0.25826 0.25545 0.25450 0.25204 0.25384 0.25420 0.25276 0.254436 1/8 1/8 0.12839 0.12814 0.12966 0.12763 0.12745 0.12718 0.12765 0.128014 1/15 1/16 0.06786 0.06863 0.06758 0.06796 0.06811 0.06868 0.06873 0.068221 1/30 1/32 0.03382 0.03383 0.03401 0.03485 0.03404 0.03500 0.03338 0.034133 1/60 1/64 0.01520 0.01455 0.01468 0.01483 0.01478 0.01484 0.01476 0.014806 1/125 1/128 0.00754 0.00763 0.00746 0.00739 0.00761 0.00747 0.00762 0.007531 1/250 1/256 0.00369 0.00381 0.00379 0.00387 0.00385 0.00381 0.00384 0.003809 1/400 1/409 0.00269 0.00276 0.00274 0.00266 0.00274 0.00276 0.00271 0.002723
Another thing to remember in Digital cameras is that Middle grey of sRGB on a scale of 0-255 is not 127 its 100. when the linear data is taken from the A/D and the sRGB curves applied middle grey is pushed to 100. This is why Adobe made ADOBERGB its curve keeps middle in the middle. I think its about the only one that does do that because while it has a lot of advantages over sRGB pretty much everywhere there are other profiles like Prophoto or with higher end digitals they have custom profiles for each batch of chips and that is put into the camera. Either way your digital light meter in the camera is set to compensate for the profile you chose so if you are using an SLR as your meter for large format make sure your camera is set to adobeRGB.
I also don't agree about over exposing neg film. Usually when people aren't getting exposure to start at base+fog its because you haven't metered correctly or tested their film batch properly. Before we shoot a movie with film we buy the whole movie worth of a batch and then put a hold an addition 50% to 100% more. Then we take 2-4 random 100' rolls from that batch to shoot and process in the manner we expect to shoot the movie. Then once we know b+f we then (alla the zone system) will test 2 more roles. +1 and -1 stop. then go crazy from there if the movie dictates it. LIke shooting -1 then processing +1 and vis versa. Basically why people over expose is because their meter is out and has been out and they never tested their film. I had a conversation with Claudio Miranda about this very thing because a lot of DP where shooting +1/3 to +1/2. We always just got a clip test from first roll messured on the densitometer. (standard practice at all good labs) Their reason for doing this was you have a lot of interneg steps and then prints so the highlights would mud up. but that is a pretty insignificant amount when you have 12-15+ stops of latitude. (vision 3 is amazing amazing stuff) In stills world thats Ektar. If you like that look from over exposing then great but Its basically a wives tale. Especially now that you won't probably be printing directly from the neg but getting is scanned. In that case the extra density in the highlights will hurt more then help.
On Tue, Apr 1, 2014 at 7:56 AM, karl shah-jenner <shahjen@xxxxxxxxxxxx> wrote:
Rand wrote:shutter speeds and apertures are far from accurate even in brand new modern camera - t stops were the standard for accuracy.
Set aperture to f8.3 or whatever fraction the shutter speed is off by. But
you are going to need to test to even know what the shutter is actually
producing speed wise. Its probably not very accurate any more.
On Mar 31, 2014 4:32 AM, "Jonathan Turner" <pictures@xxxxxxxxxxxxxxxxxxx>
A time back I tested a whole bunch of cameras and the only things close to accurate were Pentax K1000's with the old cloth shutter.. their accuracy across a dozen or so cameras was within 10% of stated speeds. The electric cameras of the day (Canon T90's, EOS's Minolta and Nikon AF cameras) varied by as much as 100% from the stated speeds - with a stated speed of 1/2000 and 1/4000 being identical - generally they were out across the full range between 12-60%
Apertures similarly are far from their stated values in a lot of lenses, and seemed more guides than anything hard and fast.. and as anyone who's used an enlarger knows, opening a lens to f5.6 and closing a lens to 5.6 will produce 2 different apertures. Only a small difference, but if you're aiming for precision the guide was always either stop down or up, not both. And of course the marked aperture assumes the lens IS the focal length it claims to be. a 43mm lens marked as a 50mm with apertures appropriate for a 50mm aint going to be accurate.
So while the shutter speeds may be those odd variants we don't see so much any more, odds are the OP can treat them as being the same as the more familiar speeds unless the exposures are way off.
Of course the easy way to test and see for sure is to use the soundcard (microphone input) on a computer and record the shutter speed for evaluation.. bearing in mind that leaf shutter speeds are pigish things. where do you measure the speed? the center of the lens? te edge? if near the edge are you measuring under an opeing blade or a point where the blade moves ou the way quickest?
Best bet is in the middle witha diffuser under the lens, then look at the soundcard output and work from when the lens is allowing about 50% of the light through to when it's closed of to 50% of the light.., or 30% depending who you ask =D
Here's two simple shutter speed tester circuits and guides that i just googled:
http://www.mraggett.co.uk/shuttertester/shuttertester.htm
http://www.willegal.net/photo/repair/shuttertester.htm
To repeat what others have said however, neg film won't just tolerate longer exposures but will give you better images if 'over' exposed - increased density gets you off the toe of the film's sensitivity and colours will definately be more saturated.f8 1/100
I recently bought an old large format field camera that came with a lens
which is so old it has shutter speeds that don't correspond with my light
meter; it has 5th, 10th, 25th, 50th, 100th, 200th, instead of the normal
shutter speeds (8th, 15th, 30th, 60th etc.)
So my problem is trying to work out what the correct exposure should
be...working from my meter. I'm shooting colour negative, so I'm guessing
it can take a bit of latitude either way, but can't quite work out if I
should go with an exposure that is slightly over, or slightly under what
the meter says. For example, if my meter reading is F8/125th, should I
shoot at F8/100th, or F8/200th?
5th, treat as 1/4
10th " 1/8
1/25th " 1/30
1/50th " 1/60
100th " 1/125
1/200th " 1/250
k
