Shutter speed question.

[minicoop1985]

I understand how a shutter works. Up to the flash sync speed, one curtain opens, then the other one shuts after the whole sensor is exposed. After that, there is a gap between the two curtains and only part of the sensor is exposed at a time until the gap travels over the whole sensor. OK, so here's my question. Do the shutter curtains themselves travel at the same speed when shooting 1/250 (sync) and 1/8000 (max), and just the gap changes? Thanks.

 

[Derrel]

As I understand it in most modern focal plane shutters, the most common way to time out the faster speeds is by keeping the curtain travel speed typically consistent at those higher speeds, but varying the slit's width, in order to achieve the different shutter speeds. This .PDF from Pentax might help. http://www.pentax-manuals.com/manuals/service/focal plane shutters.pdf

I am NOT a camera shutter expert...so this might not be correct for all "small", modern focal plane shutters.

I think on some of the older focal plane shutters in mechanical cameras, like say the Speed Graphic's in-body shutter, there is a use of different degrees of spring tensioning, which is feasible due to the mechanical, key-wound nature, and the dual-control system with the mechanical tensioning system, where you, the user, can mechanically "tighten up" or "loosen up" the tensioning with the external levers, and then read off what will be the resulting shutter speed on the chart, based on slit width, and tension. That is a slow, clunky system...but on a single-shot camera...it works.

As you can see, my Speed Graphic has this nifty metal plate...there are SIX different degrees of spring tension, and FOUR different curtain "aperture widths".

 

[minicoop1985]

Oh boy, that looks like a trip to figure out what all that stuff even MEANS.

 

[Vtec44]

To be honest I have no idea. I just want to take pretty pictures and not design a whole new camera.

 

[DavidVote]

I saw this video on youtube a while ago. Blew my mind

Skip to 2:58 for the shutter action.

 

[480sparky]

They travel at the same linear speed. What changes is the space between them.

 

[bratkinson]

Maybe two years ago already, someone posted the link to this video which clearly explains the shutter action and timing with a flash. I got a very good understanding how it all works from this video.

 

[minicoop1985]

I saw this video on youtube a while ago. Blew my mind

Skip to 2:58 for the shutter action.

This is the video that made me wonder about this. They appear to be the same there, but I wasn't sure.

They travel at the same linear speed. What changes is the space between them.

I figured this was the case. Excellent, we have an answer.

 

[Bebulamar]

The shutter curtains travel at the same speed from 30 sec to 1/8000 sec. They do accelerate so the speed isn't exactly one speed across the sensor plane. Both curtains should have the same behavior to avoid uneven exposure across the sensor. The only difference is the time between the first curtain is released and the release of the second curtain.