Why Leaf Shutter Lenses Matter (2013)
kern-photo.com
kern-photo.com
Typical DSLR shutters are focal-plane shutters, which mean they open and close directly above the image sensor. They are mechanically primed, and when triggered, the "first curtain" opens across the sensor, followed by the second curtain after a brief delay corresponding to the relevant exposure time.
In the case of very fast shutter speeds (depending on the camera, typically 1/250s or faster), the second curtain begins its traversal of the sensor before the first curtain is fully open. This means that every portion of the sensor is exposed for the appropriate amount of time, but that not every portion of the sensor is exposed at the exact same time. This is due to mechanical limitations, and is hard to get around.
In general, this isn't an issue. However, flashes and studio strobes are of a very short duration - often 1/10000th of a second or less. In the case of a focal plane shutter, this can mean that not the entire sensor will be exposed to the flash's light, causing a stripe in the final image.
There have been various ways to compensate for this - for example, high-speed flash synchronization that fires the flash at lower power levels several times during the exposure such that each portion of the image sensor is properly exposed.
In earlier DSLRs (Nikon D50 and D70 models with the 6MP Sony CCD), a "digital shutter" was used, which allowed for native flash syncing at high speeds - the mechanical shutter only operated up to its "sync limit" of 1/250, and the digital shutter took over at speeds higher than that.
In comparison, leaf shutters always open fully, which means that there's a period where, if a flash is fired, the entirety of the sensor will be exposed evenly to that flash. Because of the very short duration of the flash, shutter speed does not affect how much of the flash's light falls on the sensor, and can be used to control for background light instead, as compared to aperture and ISO controls that would affect both background light and the impact of the flash's light in the overall image.
Edit: Thanks a lot for the explanations
A Fujifilm X100F can make use of it's supplementary electronic shutter (in place of its leaf shutter) to simulate rear curtain sync.
Basically, focal plane shutter didn't get in the way of the viewer's light path since they were behind the mirror. They were cheaper to make, more reliable, and operated more consistently at the rated speeds. They were almost certainly more durable. Tungsten focal plane shutters can be rated for a 100,000 activations.
That speed does come at a cost, though, since there is a point at which you cannot expose the entire sensor at once. (That's also true of rolling electronic shutters, by the way.) Flash needs to be worked around in various ways, and anything moving in the frame will suffer distortion.
I still have good reasons to use an old Nikon in some circumstances (lower resolution requirements, high ambient light levels and flash). While they do have focal plane shutters, they only go up to 1/250 of a second. Faster than that and you're using a global electronic shutter, which doesn't reduce effective aperture when the lens is wide-open or nearly so, but still expose the entire sensor in one go. That means I can use a higher shutter speed to control the ambient exposure while using very low flash power. That means no waiting for recycling or carrying around large amounts of lighting equipment.
1. Very fast natural light shutter speeds (i.e. beyond 1/8000th second), whereas most leaf shutters might hit 1/500th or greater. He talks about some very expensive lenses that can go to 1/1600th, but this is fairly extreme.
The downside is a slower (1/200 - 1/250th) flash sync speed.
https://www.youtube.com/watch?v=CmjeCchGRQo&feature=youtu.be...
Flash photography is a balancing act between the light that comes from the flash strobes and the light of the environment. It's very popular these days to take portraits where the background is blurred, often significantly, but the subject is still in sharp focus. Background blurring is a product of the physical aperture of the lens and the distance to the subject. Opening the lens up to create more blur in the out-of-focus areas requires that the shutter speed be increased to compensate for the additional light entering the camera. A typical sunny day outdoor exposure might be f/2.8 at 1/3200s. This is far beyond the typical sync speed of a focal plane camera.
One alternative method is to place neutral density filters (darkening filters) over the camera lens (limiting the light entering the lens, but not increasing the depth of focus). The disadvantage is this method requires more light be generated by the strobes, shortening battery life, and generating more heat, and possibly more discomfort for your subjects.
As an aside, leaf shutters used to be quite commonplace until SLRs became popular (Leaf shutter SLRs were complicated and hard to repair). Even some of the most rudimentary leaf-shutter cameras from the 1950s could sync at higher speeds than the latest high-end SLRs.
I found this to be a very helpful explanation of why I would want to use a leaf shutter. TFA explains it in terms of your flash "competing with ambient light", and shows a lot of sample pictures of a properly exposed subject over an underexposed background. While visually interesting, it's probably not an effect I would want to go for when taking pictures of my kids.
Putting it in terms of being able to use the largest aperture possible in broad daylight makes more sense. There have been plenty of situations where I have been shooting in harsh daylight at f/1.7, and would have liked to use my pop-up flash to soften the light a bit, but the camera doesn't allow it due to max sync speed limitations.
Unfortunately it doesn't sound like leaf-shutter lenses are the solution for me, as the $1800 minimum for a single leaf shutter lens is more than I am willing to pay for an entire camera + lens setup.
That said, they're a real pain the neck to actually use, since you have to compose and focus, cock the shutter on the lens, release the shutter on the camera body (bulb mode or a long exposure), then fire the shutter on the lens using a cable release, then after the body is finished, open up the lens again.
The X100F is interesting for having both a leaf shutter and an electronic shutter.
Also good for high speed flash are the old Nikon 6MP cameras. I have an old D70 somewhere that I've used for high speed sports portraits.
Apart from the small image size it's a great camera. You can sync from the hot shoe at any speed, although practically this is limited by the t.5 time of your flash gun. For a Nikon SB-800 and the sort of power I was using that was about SS 1/2000.
If only that 6MP sensor had a broader ISO range. If you're not shooting for the big print, 6MP goes a long way.
That said, 1/500 is actually very good at close-ish portrait distances, like 3 meters or so. Take a typical flash unit with GN 36 and ISO 100 sensitivity. Underexposing ambient light by one stop in direct sunlight means about 1/500 at f/11, so you need a guide number of (3 meters) x (11 f-number) = 33.
Incidentally, digital cameras with electronic shutters can do this much cheaper, but for various reasons nice cameras do not generally use electronic shutters.
And you can get leaf-shutter lenses for fairly cheap. You can even get fantastic, beautiful leaf-shutter lenses with sharp images and big apertures for cheap. Old photo studios have been getting rid of them in the switch to digital. These lenses are amazing, they just don't work with the camera system you want to use them with.
I admit that I haven't thought about this for a while (I don't actually use flash a lot) but my impression was that most focal-plane shutters are rolling shutters or moving slits of some sort; at high speeds there's no point where the frame is completely open. Whereas leaf shutters have that at all speeds.
Most of the leaf-shutter lenses I have are for my old MF and LF film cameras. He's right about them being like watches. One real issue with using older lenses is that there aren't a lot of good repair folks left who know how to service them. I've got a real nice vintage Konica rangefinder with a busted shutter and there's literally one guy who might have the parts.
P.S. see above comment for better explanation.
The D40 sensor is not great by today’s standards, though.
The strobe has spread the energy stored in its capacitors across a series of small flashes instead of one large one.
Has that been solved now for small strobes (flash guns)?
By using a leaf shutter and a real high sync speed an X100 can use a tiny on-axis fill to do the work of a larger pulsing HSS system.
Various lens parameters can be communicated to the camera, including static lens capabilities but also dynamic factors such as the current manual focus distance, current manual aperture, or focus mode.
So yes, they could do that. But some systems would be designed with the assumption that all lenses will have shutters, or that the user of lenses with shutters will set the camera shutter to remain open.
Sometimes the shutter release "button" is part of the lens instead of the camera.