Why mechanical shutter on dslr?

[Robin Usagani]

I was just thinking why DSLRs use mechanical shutter and are limited to shutter sync speed for flash photography. Can't they just turn the sensor on and off to whatever shutter speed you want? I apologize if this is a stupid question.

 

[Hickeydog]

Because the viewfinder wouldn't work, then. That's the point of a SLR: You see exactly what the lens sees, exactly when the lens sees it.

 

[Bend The Light]

Because the viewfinder wouldn't work, then. That's the point of a SLR: You see exactly what the lens sees, exactly when the lens sees it.

But with the advent of mirrorless cameras, this is not necessary. The digital viewfinder could be made to display exactly what the sensor sees, the sensor needs to be on already to do that (whether liveview or though a digital viewfinder). You would just need something that tells the camera to start and stop recording what the sensor is already capturing.

So it already IS done...in any compact camera...

 

[Big Mike]

Check out the Nikon D70 (and one or two other DSLR models). It has a much higher flash sync speed because (I think) they use an 'electronic' shutter, not a a mechanical one...although, they may have a mechanical shutter as well...I'm not sure.

One reason why (I think) electronic viewfinders are only now starting to appear on higher end cameras, is because they have always been a bit slow. As in, they were never really 'real time' and they couldn't keep up very well.

 

[Helen B]

Because the viewfinder wouldn't work, then. That's the point of a SLR: You see exactly what the lens sees, exactly when the lens sees it.

My emphasis on the exactly when. You don't get that with live view, you get slightly old data, particularly in low light.

There are DSLRs that use an electronic shutter at speeds faster than the sync speed of the mechanical shutter.

Also remember that the shutter and mirror protect the sensor to some extent during lens changing. Battery life is lower when live view is used.

Some of these reasons apply more to the mirror than the shutter, in fairness.

One main reason is the way in which a CCD or CMOS is read. If readout occurs in the dark, the entire image can be read at once, so motion artifacts are minimised. If the sensor is read while light is falling on it the timing may result in motion artifacts between photosite rows. Mirrors are not lightproof if they allow some light through for focus and/or exposure, so can't be used to guarantee that the sensor is in the dark during readout (unless the secondary mirror flipped up to close the window in the main mirror - but that would be complex).

Even when used in live view, my Nikon closes the shutter to stop live view, opens the shutter to take the exposure, then closes the shutter to read the data, then re-opens for live view. (It also waves the mirror around for no apparent reason...)

Best,
Helen

 

[dakkon76]

Along with what others have said, it's still probably the best way to get the image from the camera to your eye when looking through the eye piece. The only other way to do the same thing is to add yet another display to the camera - and you're still stuck with the video lag. Not to mention, you're not going to get nearly as sharp a picture as you do off of a mirror on a display that small.

 

[Forkie]

I was just thinking why DSLRs use mechanical shutter and are limited to shutter sync speed for flash photography. Can't they just turn the sensor on and off to whatever shutter speed you want? I apologize if this is a stupid question.

Isn't that just what P&S cameras do? I thought the main problem with an electronic "sensor on/off" system was shutter lag.

 

[Big Mike]

If you really want to sync your flash at any speed, go get something with a leaf shutter system (probably a MF camera).

 

[Robin Usagani]

They have very smart people working for them, they can figure it out. Theres got to be a way to make it so that you can see trough the glass without getting light leak from the view finder and being able to turn on and off sensor just like that.

 

[Hickeydog]

And you would also look like a P&S who just bought a DSLR if you're looking at the screen instead of through the viewfinder.

Always gotta consider how you look taking your photos, right?
/sarcasm....

 

[Destin]

Nikon d70 is old but will give you unlimited sync speed due to it's electronic shutter

 

[Robin Usagani]

Not familiar with Nikon.. why did they stop doing that?

Nikon d70 is old but will give you unlimited sync speed due to it's electronic shutter

 

[KmH]

The Nikon D40/D70/D70s all had electromagnetic and mechanically controlled vertical-travel focal-plane shutters.

However, mechanical shutter control was only used up to 1/250. At faster shutter speeds the image sensor is turned on/off electronically, though the flash can still be synced to the rear curtain (second curtain in Canon speak).

The feature first appeared the D1.

Flash sync at faster than 1/500 with those Nikon cameras can only be accomplished with 'dumb' speedlights.

 

[Overread14 2]

I've seen some custom setups (made out of computer CD trays I think or might be harddisk?) which allowed for a faster shutter for higher speed snyc; though it was for specialist use and attached to the end of the lens as a light blocker; essentially you'd shoot in bulb mode or with a slow enough shutter speed and then trip the external shutter attachment with the lights to make the exposure.

 

[Tony S]

The original Canon 1D had that feature even though is still had a shutter (my memory is fading but I believe it was a CCD sensor before they went to CMOS), one of the best things about that camera was being able to sync at 1/500 (handy with studio strobes) and go to High-Speed sync (FP Flash) - up to 1/16,000 sec with a dedicated Canon flash.