Are the higher shutter speeds on large format lenses always off?

[fotopfw]

LF is not for horse races, I've never been in a situation that I needed a faster shutter speed than 1/60. In landscapes, even longer times. I am aware that fast shutter times could be unreliable, so I would never opt for using those. With people, studio, flash stops everything, fast shutter speeds again not necessary.

[domaz]

LF is not for horse races, I've never been in a situation that I needed a faster shutter speed than 1/60. In landscapes, even longer times. I am aware that fast shutter times could be unreliable, so I would never opt for using those. With people, studio, flash stops everything, fast shutter speeds again not necessary.

This totally depends on your style of photography though. Some people shoot for bokeh. Ever try to shoot a f/2.5 lens wide open with 400 speed film? Suddenly even the 1/1000 shutter speed on your focal plane shutter camera won't be fast enough.

[GoodOldNorm]

Not to be flippant, but after 40 years of LF photography I've never used a speed above 1/60. I would highly doubt that the faster speeds are accurate..

Nothing to worry about then

[Bernice Loui]

Shutter speed of 1/60 sec is not that useful. Consider if the commonly used aperture is f22 (or smaller), in bright sun with ISO 100 speed film is not going to be 1/125 sec shutter speed. The belief of needing accurate high shutter speeds appears to be a carry over from smaller film and digital based imager cameras.

~View camera image making is not the same and the needs-priorities of smaller film formats or digital based imaging should not be projected-extrapolated to sheet film-view camera based images.

Accurate slow speeds is more useful for LF image making. Having a shutter that could time down accurately to 8 seconds (or longer) is more useful than an accurate shutter speed of 1/125 sec or 1/60 sec.

Shutter speed accuracy of 1/32 second and slower is where shutter speed accuracy is important.


Bernice

[Pere Casals]

I have four lenses that I have tested with a shutter speed tester. Most of the shutter speeds are as they should be apart from the 1/250 and Higher speeds. Is it common for the higher speeds to be slow by 1/2- 1 stop?

Higher speeds are not always slower, I measured 1/500 for the 1/400 marked in an old compur of a Symmar convertible.

Best, buy a shutter tester (from $15) and know how your real speeds are, and if the same speed is accurately repeated.

Shutters when new they were sold with a -/+30% tolerance, so 1/30 could be 1/20 or 1/40, which is a full stop range, and warranty was not to be applied because gear was "in specs". So a new shutter could expose 1 stop different than another one.

...this was when new !!! after some decades anything can happen. Some people claim that TMX has to be exposed (say) EI 80 instead 100 but many have never tested their shutters

Negative film has a wide highlight latitude and nothing bad happens if you overexpose a bit as a safety factor, but if you are serious about metering you want to know the real speeds, in special if you shot slides.

[Jody_S]

Someone who remembers their integral calculus from uni could do the calculation of the average amount of light that passes through a shutter given that the blades open then immediately close, so the light reaching the film has to be calculated from the moment light passes through cracks between the shutter blades until those cracks close again. The shutter 'speed' in the center will be very different from the edge of the shutter in the center of one of the blades. In practice, a high shutter speed will act like a reverse center filter, letting far more light in the center of the lens than on the periphery. Given that the only practical use for high speeds in normal photography is for flash photography, so long as the room is dark the limitations of the leaf shutter have no effect on usage; the flash only fires once the blades are fully open. Of course math might not be necessary, a simple apparatus that measures total light passing through a shutter connected to any advanced oscilloscope will allow the necessary calculation, as they mosty have integration functions now.

If you calculate the total volume of light that passes through the shutter from start of cycle until the end, and average that over the total area of the shutter to get the average open time for the entire area, that calculated average might be closer to the nominal shutter speed. So a 1/400s speed might have 1/1000s at 5 points around the periphery, and 1/150s in the center, but averaged over the area that might come out to close to 1/400s.

[Whir-Click]

Dan, Jim, and Jody hit the nail on the head. The observation that top speeds seem 1/2 to 1 stop slow reflects the limitations of testing leaf shutters with commonly available equipment. At the fastest speeds on any leaf shutter, the efficiency (the time it takes for the blades to open and close fully) has a significant impact.

Simple testers measure the total time from when the shutter begins to open until the shutter is fully closed. However, shutter blades are still obscuring the aperture for a significant portion of this total time. The time the blades are fully open is significantly shorter than the total time the blades spend opening and closing. The effective shutter speed, which is engraved on the shutter, is the halfway point between the total and full open times and delivers the desired exposure.

Consistent with Rayt’s experience, most modern shutters perform at their stated, effective shutter speeds, within 1/3 stop. The top speeds on older shutters may be slower, but can still be reliable.

Bottom line: if your smartphone or computer shutter speed tester shows that your slow and medium speeds are accurate, but your top speeds are 1/2 to 1 stop slow, it’s a good indication that everything is actually working as intended.

I’ve tried to summarize and illustrate this on my website: https://alphaxbetax.com/services/#Speed-Test

[cowanw]

In practice, a high shutter speed will act like a reverse center filter, letting far more light in the center of the lens than on the periphery.

I don't expect that you are saying that smaller shutter opening i.e. smaller fstops do not cover the entire film format intended. Insofar as the lens spreads the beam out whether the light comes through the center or the periphery of the lens, the reverse center filter analogy seems faulty. Eh?

[Drew Wiley]

I've only had one LF shutter where the top speed was accurate. On all the others, mostly purchased new, it was way off, even if all the lower speeds were spot on. I have a serious shutter tester which cost a hecka lot more than $15. But this is a non-issue. I never use high speeds in LF work anyway.

[Jody_S]

I don't expect that you are saying that smaller shutter opening i.e. smaller fstops do not cover the entire film format intended. Insofar as the lens spreads the beam out whether the light comes through the center or the periphery of the lens, the reverse center filter analogy seems faulty. Eh?

This applies at wide-open apertures since the shutter blades are usually in very close proximity to the aperture blades, but there are few circumstances where you would stop down to f32 then shoot at 1/400s. Maybe if you're trying to photograph a nuclear explosion, or you find a stash of 1600 ISO film that you must use in full sun.

So if you're shooting at full aperture to get shallow DoF, and you need that 1/400s, its easy to see that the center part of the lens is going to get far more light than the outer extremity where the last part of the shutter blade retracts outside the optical path. Now does this act as a reverse center filter or does it affect DoF, given that it's at the optical node of the lens? I suppose it depends on the lens type you're using? If you mount your 1860s f3.5 Petzval in front of a Shanel 5 shutter (or use a front-mounted LUC shutter on 'Instant'), you are definitely getting a reverse center filter at top speed, which is what you would be using (the lens' image circle will also be a factor, if you are using the entire field or just the center). With a modern plasmat and center-mounted shutter, I don't know enough about optics to say exactly how it will affect the image. I've never shot lf at high speeds, but I've used plenty of 35mm rangefinders with leaf shutters and plasmat lenses, I've never noticed dark corners. However, I don't recall ever shooting at full aperture either, since I mostly used zone focus for street photography.