Is there a need for a shutter?

[Joel Bookhammer]

I havent really thought about this questionindepth, but the question popped into my head on the way home from doing senior pictures yesterday. Is there a need for a "shutter" in a digital camera? If I understand it correctly (which I probly dont) the sensor is on for the duration of the exposure. So lets say you had a exposure of 1/125 if the sensor is on for 1/125 is there a need for a shutter staying open for the same duration? If there wasnt sync speeds could essentially go as high as well....Im not really sure because there wouldnt be a mechanical shutter having to move.


Let me know what you think, Im no expert just something I was thinking about last evening.


Thanks


Joel

[Sean Setters]

From what I understand...


Actually, some Nikon cameras and the orginal 1D (I think) have electronic shutters in which the sensor simply turned on for the duration of the shutter speed. The technology does push the max flash sync speed well beyond 1/250 sec (I've heard some Nikon shooters pushing 1/8000 sec, although that also restricts how much flash output is recorded and thus you lose several stops of light). The problem with the technology, however,is consistency. At the time the technology was introduced, the exposures would vary slightly from shot to shot even when the same settings were used across all the frames. Also, the sensors tended to fail after a relatively brief period of time. Those limitationshave keptthe technology from being used in even the most recent high-end SLRs.

[nrdavis]

You're right. To some degree there isn't much need for a mechanical shutter any longer. In fact, some (or maybe a lot, I'm not sure) lower end point and shoot digital cameras don't have a physical shutter. They do exactly as you say, turn the sensor on for the duration of the exposure, and then turn it off.


With DSLRs, the shutter does serve one distinct purpose that could not be solved by an electronic shutter. It covers and protects the sensor during all the time that you're not taking a photo. Figure a typical exposure time is 1/125 second, and you might take 125,000 photos during the life of your DSLR. This would mean that the sensor is exposed to the dust and grime of the relatively unclean mirror box, for only about 1,000 seconds, or less than 17 minutes, during the entire life of the camera. Think of how much more dust you would get on the sensor if the shutter was open all the time (or not even there).


Point and shoot cameras get around this by placing the sensor in what is effectively a hermetically sealed box. No lens changes, means no dust should ever get inside, theoretically.


I'm sure there are a plethora of other good reasons why mechanical shutters are still used, but this is one that came to my mind.

[DavidEccleston]

The Nikon D40's manual says not to take pictures with the sun in the frame, as it will melt the camera's innards. Now, ignoring the thousands of pictures online with the sun in the frame, there may be a point. The lens will concentrate the sun light into a small space on the sensor. Without a shutter, you may accidentally leave the sensor in direct concentrated sunlight for an extended period of time. I'm going to wager that the sensor isn't really designed to handle that.

[Joel Bookhammer]

Good points about dust and exposure to the sun. The main reason for asking the question is, is that I am diving into the world of strobes and it would be great to be able to sync at lets say 1/2000. Right now Im limited to 1/250 on my 40D (without jerry rigging something together).


Instead of getting rid of the shutter completely what about a different design, then whats currently being used on slr's or any camera currently in production. Something new and exciting. []


thanks


Joel

[Sean Setters]

Instead of getting rid of the shutter completely what about a different design, then whats currently being used on slr's or any camera currently in production. Something new and exciting. [img]/emoticons/emotion-1.gif[/img]


thanks


Joel
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As to what's being developed right now, I do not know. However, there are a couple of tricks you can do with 1 580EX(II):


1) Rear-curtain sync: Use optical triggering. You can have the optical sensors at the point of the off-camera flashes as long as youron-camera580EX's light hits the optical sensor. However, this can prove less effective in bright sun. An even better trick is to attach a radio transmitter to an optical slave (like putting a Cybersync CST to a CTR-301p) and then attaching that rig to your on-camera 580EX. Voila, rear-curtain sync with off-camera flashes.


2) High-speed sync: Same setup as above but set your 580EX to high-speed sync. Set the off-camera flashes to full-power (this helps ensure the best flash coverage). The optical triggering allows you to push past your max sync speed. Keep in mind that the off-camera flashes' output diminishes quickly as the shutter speed goes up. I tested this particular trick after learning about it a couple of weeks ago. I was able to get somewhere around 1/600 sec without the shutter blocking the sensor (although I did decide anything past that diminished the flash's outputso much that it would renderthe flashalmost useless).

[ShutterbugJohan]

In fact, some (or maybe a lot, I'm not sure)
lower end point and shoot digital cameras don't have a physical
shutter. They do exactly as you say, turn the sensor on for the
duration of the exposure, and then turn it off.

As far as I know, no current point-and-shoots have a mechanical shutter. The Micro Four-Thirds also lack a physical shutter.

Actually, some Nikon cameras and the orginal 1D (I think) have electronic shutters in which the sensor simply turned on for the duration of the shutter speed.

I once heard that that is the case with all CCD sensors (vs. CMOS), but I do not know if that is true or not. :-(

[Jarhead5811]

With DSLRs, the shutter does serve one distinct purpose that could not be solved by an electronic shutter. It covers and protects the sensor during all the time that you're not taking a photo. Figure a typical exposure time is 1/125 second, and you might take 125,000 photos during the life of your DSLR. This would mean that the sensor is exposed to the dust and grime of the relatively unclean mirror box, for only about 1,000 seconds, or less than 17 minutes, during the entire life of the camera. Think of how much more dust you would get on the sensor if the shutter was open all the time (or not even there).

True, unless someone likes to use live view. Now thatI think about it. It's just another argument against live view.

[lculpin]

HSS is nice in that it's built into Canon's Wireless ETTL2... and 2nd curtain is wicked for a LOT of things but unfortunately if you're shooting wireless with canon flashes then you're out of luck unless you go the Pocket Wizard route (and even then you have to fake it by setting a delay). There may be other radio transmitters out there that do this too but if you're looking at anything TTYL then it's hard to come by (and unfortunately the seemingly ill-fated radio poppers don't support it either).