View Full Version : half/third stops found in lenses.

scott russell
26-Apr-2008, 10:06
I have a 135 rodenstock 4.5 on my super graphic right now. The lens only stops down to F32, and the slowest shutter speed before bulb is 1/2sec. In addition, it only operates in full stops which makes exposing things precisely very hard. I was just wondering if this is only common with older/less professional type lenses. I'll probably be spending some money on a nikkor 135 or 150 in the future and I was wondering if any of these modern lenses have more exposure increments (I have never examined a LF lens other than mine, so I don't really have a clue).

26-Apr-2008, 10:10
I believe that all shutters are graduated in full stops. However many (all?) modern shutters have third stop marks for aperture, and while these are not marked it would be easy enough to figure where the half/third stops would fall on a shutter such as that for your rodenstock.

26-Apr-2008, 12:03
I rarely feel the need to be exceptionally precise in exposure (what's a half-stop matter, after all, in any media except transparency)... but the greatest amount of adjustability is always going to be with the aperture. Unlike shutter speed settings, no matter how aperture is marked (whole, half, or thirds) one can always estimate and set in between the markings.

Frank Petronio
26-Apr-2008, 12:37
It depends on the shutter used, not the lens. Late model Prontors have 1/3 stop detents, it is a nice feature. The most popular shutters - Copals - have no detents. But you can open and close the aperture to whatever you want.

Rob Champagne
26-Apr-2008, 12:42
current copal shutters come with 1/3rd stop detents or no detents depending on which you order. Obviously the no detents version can be set however accurately you can judge the positioning but to a 1/5th or even a 1/10stop is easily doable if you can see the markings and arrow.

Frank Petronio
26-Apr-2008, 14:31
1/3 stop makes a significant difference when you're shooting transparencies, although I wouldn't bracket negative film that closely... more like 1/2 or 2/3 of a stop for bracket outdoors, normal subjects.

Actually I don't bracket negative film unless it is something extreme, like shooting very high key subjects with backlighting maybe?

scott russell
26-Apr-2008, 16:48
I guess I should have specified that i've been shooting a lot of slide film, so half stops too help, especially when the bellows is extended and it tells me i need to compensate 1.7 stops of something silly like that.

Alan Davenport
26-Apr-2008, 20:08
...wouldn't bracket negative film that closely... more like 1/2 or 2/3 of a stop for bracket outdoors...

Frank, I know you didn't intend to send me down Memory Lane with that statement, but thanks for doing so anyway! My first serious photographic work and training came at the hands of a couple of old press photographers, the kind who had grown up with a Speed Graphic and a pocket full of Edison threaded flashbulbs. I've never forgotten one of the things Mac tried to impress on me as gospel: "A stop is the smallest exposure change that makes any difference." We know better, but when I put myself into his shoes and experiences, it makes perfect sense. In his press days, he needed to get a negative that could make a glossy print which would eventually end up as a halftone image on a sheet of newsprint. Indeed, if one exposure wasn't good, the next full stop away would do just fine...

26-Apr-2008, 20:14
Allan... I know who Edison is (was), but who is "Mac?"

Frank Petronio
26-Apr-2008, 20:40
yeah well even now, when you do a long nighttime exposure and you really can't afford to wait for a Polaroid because of changing conditions, sometimes you just have to do wild, what-the-hell brackets, a stop or more at a time, but that is pretty rare.

But for 4x5 photojournalism I can perfectly understand why it would be business as usual.

Mark Sawyer
26-Apr-2008, 21:36
My favored method is to measure the bellows extension, decide the desired f/stop, divide to find the diameter, and set the aperture by measuring with a small ruler while ignoring the engraved stops. A very simple, flexible, and elegant solution, but I've never heard of anyone else doing it that way...

Frank Petronio
26-Apr-2008, 21:58
How do you measure it through the lens? Or do you remove the front element each time?

Helen Bach
27-Apr-2008, 06:41
You should measure it through the lens - it's the entrance pupil diameter that you want, not the diameter of the hole in the aperture blades. I wonder how accurately you can measure small diameters in the field, however.


Brian Ellis
27-Apr-2008, 08:42
I think the importance of a stop with negative film depends in large part on the range of the scene. If the darkest important shadows and brightest important highlights fall within Zone IV to Zone VII then a stop either way usually won't make a major difference in terms of how printable the negative is. Assuming proper development it should be pretty easy to make a "normal" print with either exposure. If things are borderline - e.g. Zone III or Zone VIII - then a stop under or overexposed can matter since it could lead to shadows with insufficient texture or blown highlights.

I used to make two exposures with 120 b&w film rated at half the manufacturer's rating, one at the meter reading, one at a stop more. Most of the time a "normal" print could have been made just about as easily with one as with the other. It's pretty easy to look at a contact sheet of photographs made that way and see how relatively little difference a stop usually makes with negative film.