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.
sound card are accurate to 1/32,000th of a second. use a laser module or an
LED, doesn't make any difference, as long as it's colimated to a spot - the
only variable is a slight leap and drop with diffraction at the edges and
yes I am most certain these cameras were as out as I found, Steve Hodges
and I both tested a bunch of cameras and it surprised us both. most
surprising was our T90's didn't rate compared the stack of old abused
K1000's :)
Of course those suffering confirmation bias assured us their new Nikons were
bang on perfect and the test gear must have been wrong.
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
go ahead and run your own tests and plot the error factor against the stated
shutter speeds, I think you'll be surprised. I built mine using a sound
card as its cheap, and the sample rate was vastly superior to any unit you
could buy in the day. Steve built his differently, they both agreed. I am
always suprised how with the vast capabilities of personal computers
available to most people that they are used so little in such ways. all
that discussion about the best darkroom timers, contrast analyzers and
such.. and yet every day PCs are thrown away because they're 'old'.
ridiculous.
And I am always keen to hear how people test leaf shutters since from their
inception they were always recognised as being pretty crazy ..
let me explain. you have your shutter set to 1/125th of a second, your
aperture is f45, the shutter begins to open and almost immediately it's
allowing fully all the light through the tiny aperture, way before the
shutter completes it's wide-open travel. Now you change your aperture to f2
(yes, I had a lovely f2 seiko 150mm 5x7 lens ) so you have to wait for the
shutter to be fully open for your aperture to get the full amount of light
through.. then it begins to close.
So which one got 1/125th of a second?
and what about at say f16 when there's a zigzag of shutter blades in the way
for half the exposure?
see what I'm saying Rand? not so simple.. and each design is affected by
the number of blades and the way which they open - and this differs even
within a manufacturers designated brand name with different shutter sizes.
The timing test of a Copal #1 by Jean-David Beyer <jdbeyer@xxxxxxxxxxx>
shows
that mechanical shutters are very accurate:
I haven't met Mt Beyer, I don't know his test methodology.
However, I agree mechanicals tended to be accurate. I postulated that the
permanent magnets used in hybrids such as the F1N and pure electronics may
wane in power from being slapped by the actuator (magnets dont like being
hit) in the case of faster releases, and layers of lubricant gone sticky may
cause the same parts to hold too long. Dont know for sure, but I do know
when I service sticky / too-long exposure faults in modern cameras 80% of
the time it's solved simply by wiping them with a solvent.
if you are using an SLR as your meter for large format make sure your
camera is set to adobeRGB.
might be good advice to those who'd do such a thing.
On a similar note, not sure how your physics is, but selenium cell
sensitivity has to be considered when shooting black and white film stocks
since their peak sensitivity is away from that of (most) films. but then,
the colour of the subject needs to be considered against the film
sensitivity as well.. and so forth. I don't know what the current trend in
sensors is for the most modern light meters - at one point it was
phototransistors, next photodiodes (with peaks in the yellow), then there
were 3 colour modules running comparators.. it's all guess work unless you
custom build for specifics... or accept that there's always latitude in this
sloppy photography world.
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.
you can argue that, Iand many others who rigorously test films would argue
that getting away from the toe is a better idea. Most photographers
don't/wouldn't test there film stocks, many wouldn't know how. I mean, how
many pro's do you know who buy 'pro' film because it's 'pro'? conversely
how many people do you know who buy blocks of any film and test them? I
don't think I ever knew many people who owned sensitometric equipment..
But back to why shoot off the curve? Why mess around at a curvey part of
what will rapidly become a near linear rise in sensitivity? Trying to eek
out the most 'speed' of a film is the only possible reason I could see as
valid unless you were using a very tight film like E6. Deriding people for
not shooting on the curve is silly. You've got the same gamma up the curve
for quite a way - why put up with spotty dark colours where individual
grains may/may not have geot enough exposure when you could give it a stop
more light and get rich dense colours?
Remember Agfa's much admired Ultra film the 50 ASA with the super rich,
dense colours? it wasn't a 50 ASA film. tested, It was actually a 16-180
ASA film (Ilford speed standard). But hey, they sold it and by marking it
50 ASA people 'over' exposed the film and got off the toe - subsequently
they got deep rich saturated colours even down in the dark areas.
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.
yeah I always bough handfuls of random films and shot/tested them . If I
liked them, I bought a block from the local suppliers fridge. cheap pro
film. old trick.
Basically why people
over expose is because their meter is out and has been out and they never
tested their film.
no. see above. some people may do as you say. some people wold rather
have denser, richer dark tones. all they are doing is sacrificing the
'speed' that so many people yearned for. Me, I coldn't give a rats for
shooting 400 unless I wanted grain for grains sake (even then, 'over' expose
a 400 and watch the gain all but disappear ) but most people seemed to love
400 for the speed.
heck, I rememeber being disgusted when I tested one particular 1600 E6 film
that had become popular. Inside the box were instructions that it had to be
pushed 2 stops to achieve the rated speed. Sorry, pushing does not increase
the speed very much at all, it does however change the contrast and I didn't
need to pay a premium rate to shift a films contrast!
Their reason for doing this was you have a lot
of interneg steps and then prints so the highlights would mud up.
internegs should not mud up, development can/should compensate.. if not the
development then the interneg film stock. I used a lot of black and white
interneg stock, heck, I shot with it. (of course one has to TEST their film
and development before you can go doing that..)
but Its basically a wives tale.
rubbish. please don't tell me you also go around telling folk selenium
toning is good for prints?
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.
that bit is true if you are using certain types of scanner with certain
types of software. laugh. I remember the other lecturers were all in a
pickle over the Nikon scanners inability to scan dense negs.. and I fired up
Vuescan and got damned fine results.. 'oh noes! Wee can't use Vuescan..
it's not Nikon, and Nikon is the best!' laugh.
I still have my King Conceprt RP 2001 processor, my Hope RA4 24" RA4 machien
and my Omega closed-loop 4x5 enlarger and I can mix and make my own
chemistry easily enough.. heck, I made everything for the colleges E6 when
the national supplier ran dry once.
My scanner is a Sharp JX610 so density is no issue at all. 3 colour pulsed
xenon .. it may well take half the night to multipass scan a 8x10, but the
result are more than worth it.
