leaf shutters and mirrorless system cameras

[sebastel]

this is an idea that is on my mind for some time now - just putting it down somewhere in order to get rid of it ...

by the way, talking of interchangeable lens (= system) cameras only.

mirrorless digital cameras (like the µ4/3) use a rather complex protocol for controlling the shutter actuation. the shutter needs to be open for live view, then closed to prepare the shot, then open and close for exposure, and finally opening again for live view again.

that's exactly the same kind of protocol that is necessary for system cameras using a leaf shutter. this kind of protocol has been too complex to go through with older, mirror based mechanical SLR cameras (except for the hasselblad and some rather exotic zeiss cameras, of course - the contaflex), so we got used to focal plane shutters instead.

but now in the "digital age", this type of complexity is a non issue. so, wouldn't it be the right chance to introduce leaf shutters to modern cameras again?

the advantages of leaf shutters are:

- unlimited flash synchro
- no distortion of fast moving objects
- light weight shutter blades consume less energy
- less mechanical wear
- less noisy than focal plane shutters (really very very quiet)

the disadvantages are:

- one shutter per lens means, the lens prices will be higher
- lens gets more bulky
- slower (shortest exposure time may be 1/500 sec)
- maximum aperture of the lens is limited
- lens mount needs additional connectors

taking into account these properties and requirements of leaf shutters, i sincerely doubt that they will be adopted. still i consider leaf shutters to offer an interesting alternative, even if they may be only a technical gimmick.

i also see the electronical shutter (on-sensor) to be a valid approach, but there is no such solution available by now - different to leaf shutters, which are well known since long time.

it's "doable". but would it be worth while?

cheers,
sebastian

 

[Abbazz]

the disadvantages are:

- one shutter per lens means, the lens prices will be higher
- lens gets more bulky
- slower (shortest exposure time may be 1/500 sec)
- maximum aperture of the lens is limited
- lens mount needs additional connectors

The biggest issue with between-lens shutters, as opposed to focal-plane shutters, is that they have an efficiency which varies according to the shutter speed and also to the lens aperture.

When the photographer presses the release, the blades of the shutter need a certain amount of time to open fully. During that time, the quantity of light illuminating the image plane is not what it should be. Then the shutter blades stay open during a certain amount of time, which is called the effective shutter time. During the effective time, the quantity of light reaching the image plane is nominal. Finally, the shutter blades need a certain amount of time to close again, during which the illumination decreases progressively. The efficiency of a shutter is the ratio of the effective shutter time to its total open time.

It is easy to understand that the opening and closing time of the blades doesn't vary, while the effective shutter time varies according to the speed selected by the photographer. Therefore, the efficiency varies according to the speed: for the lowest speed settings, the opening and closing time is negligible in comparison to the effective time (very good shutter efficiency), while for the highest speeds, the shutter blades begin to close immediately after finishing opening (very low efficiency).

In the same manner, the time it takes for the shutter to fully open varies according to the aperture, because the blades need to travel further away when the aperture is fully open, while they only need a very short move when the lens is used at its smallest aperture.

In short, the exact amount of illumination provided by a between-lens shutter is very difficult to determine accurately, in comparison to a focal-plane shutter. Of course, there are tables to correct the exposure time according to shutter efficiency (it is done by the firmware on a digital camera), but the correction for the lens aperture is more complicated on an interchangeable lens camera, because the effective diameter of the aperture varies with the focal length....

The leaf shutters also interfere with the lens bokeh by adding an image of the shutter blades opening to the out of focus highlights. Here's an example:

Picture linked from William Brodie-Tyrrell's website

In short, I would say that you are right when you state that the between-lens shutters were too complex for SLR cameras. In my humble opinion, the demise of the once powerful Zeiss conglomerate was caused by its stubborn use of leaf shutters in its interchangeable lens SLR cameras. Leitz was on the right path with its cloth shutter. And of course the Japanese manufacturers put the final nail in the leaf-shutter coffin with he square Copal. I am not sure we need a leaf-shutter revival for the interchangeable lens cameras 🙄.

Cheers!

Abbazz

 

[sebastel]

your points are correct, even though the derivation of the effective shutter opening time compared to the nominal openig time should be negligible, as long as the effect is smaller than (say) 25%. with fast (small!) shutter leaves, this should be easy to achieve.

please note, that my idea was to _additionally_ offer leaf shutter lenses, sou you would have the choice to use the one without losing the option of the other.

extending possibilities should not be a bad choice, no? anyway, i still assume that additional cost may not be worth while the additional value.

cheers,
sebastian

 

[Dwig]

...
that's exactly the same kind of protocol that is necessary for system cameras using a leaf shutter. this kind of protocol has been too complex to go through with older, mirror based mechanical SLR cameras (except for the hasselblad and some rather exotic zeiss cameras, of course - the contaflex)...

There's nothing about Hasselblad, the Kodak Retinas, and the other "exotic zeiss [sic] cameras" that makes them less complicated or the complication more practical.

With live view digital cameras, with the exception of Sony's semi-live view system, the overall operation is vastly less complicated than with film SLRs regardless of whether they are fixed or interchangable lens. The great advantage of using a focal plane shutter in the body is that legacy lenses can be used. A leaf shuttered system would be restricted to lenses made specifically for the camera.