
Rapatronic Camera - omosubi
https://en.wikipedia.org/wiki/Rapatronic_camera
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khazhou
Is this still state of the art for ultra-fast exposures, or is there newer
better technology?

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simcop2387
Not the state of the art, but I'd be surprised if it isn't still used in some
cases where you need lots of dark filters anyway.
[https://web.media.mit.edu/~raskar/trillionfps/](https://web.media.mit.edu/~raskar/trillionfps/)
I think has info about the state of the art for "shutters".

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VohuMana
Just curious does anyone know why this type of shutter isn't used on modern
digital cameras like DSLRs or mirrorless cameras?

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brudgers
A back of envelope exposure calculation using the Sunny 16 heuristic [1] and
assuming that high shutter speed is the rationale for using a Kerr cell
shutter [2]

Full sun bright for a "typical" scene. That's ISO 100, f16, and 1/125 seconds
for "typical" exposure [3]. To make it easy, assume an f1 lens (about as fast
as you can buy and assume t-stop equals f-stop and ignoring issues with
acceptable depth of field). An f1 lens is 8 stops faster than f16, so it
requires 1/2000 of a second exposure at ISO 100. The Raptronic shutter was
1/1,000,000 second (1 micro-second). That's nine stops faster. We're out of
lens aperture so Sunny 16 says we need 9 stops of ISO. That gives ISO 102,000.

ISO 102,000 is available on consumer grade digital cameras such as the Sony
A7S, the Pentax K1 and KP, etc. The Pentax KP goes to ISO 800K (for some
definition of 'goes') so you could theoretically shoot at f2.8 in full sun.
Theoretical if you can live with the noise and if there are not other effects
from very short shutter speeds (the equivalent of solarization from short
shutter speeds on analog film) [4] [5]

Most people want the ability to shoot in less than full sunlight. Most people
don't want to live with a high noise baseline. Most people want the ability to
achieve moderate depth of field. Most cameras are designed for a meaningful
segment of most people.

So Kerr shutter digital camera is viable. It needn't be mirrorless. In a
typical single lens reflex, the mirror already swings up out of the way before
the shutter fires. It is also possible to mount the shutter in the lens of a
single lens reflex camera. That's typical with Hasselblad, Mamiya, and some
other SLR medium format cameras.

[1]:
[https://en.wikipedia.org/wiki/Sunny_16](https://en.wikipedia.org/wiki/Sunny_16)

[2]:
[https://en.wikipedia.org/wiki/Kerr_cell_shutter](https://en.wikipedia.org/wiki/Kerr_cell_shutter)

[3]: e.g. snapshot conditions not Adams' Zone system or similar.

[4]: Just theorizing about the _possiblity_ of equivalent effects. I don't
know.

[5]: It would be interesting to know about the film stocks which allowed the
Rapatronic to avoid solarization.

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michrassena
I'm not sure you're correct about solarisation. The reversal of tone found in
solarisation is due to overexposure, see
[https://en.wikipedia.org/wiki/Solarization_(photography)](https://en.wikipedia.org/wiki/Solarization_\(photography\))

Solarisation would be a likely outcome of a too slow shutter when
photographing the nuclear explosion on typical film stocks without sufficient
filtering. It was at least as important to achieve sub-millisecond shutter
speed as it was to properly expose the film.

One thing that does typically affect film, either with too short or too long
exposures is reciprocity failure
[https://en.wikipedia.org/wiki/Reciprocity_(photography)#Reci...](https://en.wikipedia.org/wiki/Reciprocity_\(photography\)#Reciprocity_failure)
so perhaps that's what you're thinking of. It's hard to know how relevant that
is to this discussion. I'm not sure it was a consideration given how energetic
a nuclear explosion is, and reciprocity failure is found when there are not
enough photons to convert the silver halides into a latent image.

I think you're on the right track with Sunny 16, but why not use this method
to take photos of the sun itself? I've seen 16 stops recommended as the
minimum for solar filtering, so that puts it in the range of standard ISO and
f-stops, but without filtering, a high shutter speed like with the Kerr cell
is possible.

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brudgers
I agree about solarization and reciprocity failure. My bad. too late to edit.

For pictures of the sun, the short shutter speed is an alternative to filters,
but filters are inexpensive. I bought a pair for less than $20 to take
pictures during the recent solar eclipse in the US.

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HNLurker2
Imagine the fps if it took videos

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chuckleMuscle
I use one of these [1] for work. The software which comes with it asks you to
specify an fps when setting up an exposure. Typing in 66 Mfps always feels a
bit dumb!

[1] - invisiblevision.com/products/ultra-high-speed-framing/

