shutter on or off
 

Hi, if i am shooting at 720p50 should i have the shutter on auto or off,

rob.

You shouldn't have the shutter on auto. Always select an appropriate shutter speed or angle. If you are shooting 50P then choose shutter speed 100, if is 50i shutter 50. You can shoot also with shutter off, in which case the related actual shutter speeds will match your frame rate (50 for 50P). These shutter speeds are common settings, but you change them to suit the subject.

I'm shooting 1080 50i and the lowest shutter speed listed in the menu is 1/60 . . . . where do you find the lower speeds? Camera is setup for PAL.

Mark

Menu/camera set/shutter: step up or down with joystick or scroll wheel. Minimum speed is 1/33, max 1/2000. Or if you select angle you can select between 180 and 11.25 deg.

Just changed the formats around and tested the shutter speeds: both the i formats will only go down to 1/60; all the p formats go down to 1/33. Is that normal or is it my camera?

Mark

I hadn't noticed that (not using interlaced). One might expect that to cause flicker problems with 50Hz lighting. So set shutter angle 180.

shutter-off = shutter-speed of 1/framerate = 360°-shutter
So 50p/50i with shutter-off results in a shutter-speed of 1/50.
When shooting 50 or 60fps I would go in most cases with shutter-off.

Are you sure about that 1/50th? 50i is 25 fps -- I refrained from making that statement without actually measuring the exposure period. Obviously you are correct for 50P.

I think it's widely accepted that what Dominik is saying is correct.

50i is 50 interlaced frames per second so whether shooting progressive or interlaced it still has to record that many frames per second. Shutter Off = frame rate.

Ian

EX1s sensors can capture 1080p only. 1080i/720p is done by post-processing.

No, 50i is 25 fps. 50 fields/sec. I'm not saying Dominic is wrong, I was asking whether he is right. That is, fact, rather than opinion. The Phlogiston Theory of combustion was widely accepted. If the image is taken as progressive and processed out as interlaced, then shutter off is 1/25. However interlaced does require 1/50 sec difference between fields, so how would that be derived from a progressive image? Perhaps you're saying that 50i is actually 50P and the fields for 50i are derived from alternate frames? Seems a daft way to do things. You can see why I would prefer an actual measurement.

Wow, pretty obscure, Serena! Had to look that one up.

What you're saying makes sense - I'm very intersted in understanding this all better.

Exactly.
Please tell me a less daft way, if your base are progressive sensors. It's a flawless way.
Of course I checked it out long ago (I never use 50i), and the result was that with shutter-off and 50i I got a shutter-speed of 1/50.
50i also gives higher sensitivity, because the 50i-setting adds gain, to exploit the lower noise-level caused by the vertical low-pass-filter for reducing flicker.

Anyway, in both 1080/25p and 720/25p/50p (in PAL; please adjust for NTSC), shutter off is 1/25th of a second. Period.

This is the reason why - when switching shutter on, the lowest selectable shutter speed is 1/33th.

Sorry, but you are wrong. 720/50p with shutter-off gives 1/50-shutter.
No, the slowest selectable shutter-speed depends on your framerate. But it's always faster than 1/fps or 360°, because else the electronic shutter wouldn't have a job to do and then it wouldn't make any difference if it is turned on or off.

I stand corrected, Dominic (I don't have my EX1 with me at the moment, as it's with the Prime Support for an overhaul) - with 720/50p, it should be 1/50th, same as the fps.

As to the slowest selectable shutter speed, I only meant standard shutters - not the SLS, or EX Slow Shutter.

I just tried all standard-framerates and got that result:
fps slowest-shutter
24 1/32
25 1/33
30 1/40
50 1/60
60 1/60
Interestingly at 60fps the slowest selectable shutter-speed equals the framerate.

Quote:
Originally Posted by Serena Steuart
Perhaps you're saying that 50i is actually 50P and the fields for 50i are derived from alternate frames?

Exactly

Are you sure about that? 1080/50i can't be 1080/50P and fields derived from those frames 'cos the camera can't do 1080/50P. Surely 50i is derived from 25P, with alternate lines extracted to make 2 fields.
Steve

Shutter Speed
 

As i understand,25p with ''shutter off ''means 1/25 th shutter.And because of that indeed lowest shutter setting with ''shutter on'' is 1/33.you can see it if u set at 25 p shutter on or off..picture much brighter with ''shutter off''..

RR

Yes it can! It can't bring it on the sxs-cards, but it captures and processes it.
Even if the sensors would support temporal delayed odd (or even) rows, it's not a good idea, because then vertical low-pass-filerting wouldn't be possible, so it would flicker a lot on interlaced screens because of the very good MTF of the sensors+lens (the sensors don't have an appropriate optical low-pass-filter, so progressive images are very sharp). And observation shows, that it does vertical filtering on the whole 1080-rows-frames.
And what about 720/50p? If it would be derived from 1080/50i, then there would be deinterlacing-artifacts.

Yes. To be more exactly, shutter-off means the additional electronic shutter is turned off. Then the exposure time is just the result of the periodic readout and reseting of the pixels, which depends only on the framerate.

Not arguing with you Dominik, but where did you find out that the EX can do 1080/50P? I thought that was just the F23. Surely if the sensor could do it then it could feed it out of HD SDI and with the Flash XDR you'd have an F23/SR kit (more or less!) for £5000 instead of £100,000.
Steve

I read it somewhere, but I can't remember where. But more importantly it makes perfectly sense and matches perfectly with all of my experience.
For sure it can be hacked. But why doesn't Sony offer it out of the box together with recording of 4:2:2 and 50MBit/s? And why do I have to use these ridiculously overpriced sxs-cards for the little throughput of 4 MByte/s, of which almost every other flash-memory out there is capable of? Hmm, I guess it could be concerned with their marketing-strategy. ;)

I agree with your sentiments. I've got a PDW700 and wonder why they won't put 160 mb/sec I frame on it as seeming the mpeg used is capable of it as it's the same one used by the Flash XDR.
Still very dubious about the 1080/50P though, AFAIK it certainly does not come out of the HD SDI. Having said that, my PDW700 apparently has the same chip as the HDC1500 studio camera and that can do 1080/50P which mine can't so maybe it's a similar situation?
Steve

I'm waiting for that firmware upgrade that let's me overcrank 1080 24p to 60p! Okay, I'm not exactly holding my breath.

If I were putting together an opinion on this I'd suggest that the greater gain in 50i is achieved by stacking frames. If you take 2 frames (50P) to output one, then there is no point in throwing away data that can be utilised. This is how we do it in astronomy. I'm very wary of technical arguments based on "I read it somewhere". References please.

EDIT: While my point may seem "aggressive", it arises from long experience in technical discussions where difficulties often arise because people fail to differentiate between what they think and what they know. It is extremely important to make clear what is fact and what is deduced or thought to be so.

Hi People,

I just wanted to get back to the subject, if i have the camera set to 720p50 and the shutter off, is the shutter speed 1/50 ?

I have tried both setting and can not seem to see the difference, any one have a idea what is better ?

rob.

Yes, shutter off when shooting progressive 50P is 1/50 sec. However that is not stated in the user manual and in accordance with my note above I add "I believe that to be so".

Thanks for your comments.

OK, I've made some measurements. At 25P shutter off is 1/25. At 720/50P the default shutter is 1/60 (shutter on), which may be the reason you could see little difference between on/off. Shutter off is 1/50. I suppose I should repeat for 50i.

edit: yes, 50i shutter off is 1/50.

Each of two 50p-frames becomes one field of a 50i-frame. But one field has got half of the resolution of one 50p-frame, so you can add every two rows of the 50p-frame to one. And that's vertical box-low-pass-filtering with 6db-gain. ;)

Yes, of course. Would be a nice idea to stack lines (which would also give 6dB gain) but the time difference between fields has to be maintained.

The time-difference is maintained, because fieldA comes from frame1 and fieldB from frame2.
Assume you are creating a top-field-first interlaced frame out of two consecutive frames frame1 and frame2, then:
The lines 0, 2, 4, 6,... (field-A/even) of the interlaced frame are the lines 0+1, 2+3, 4+5, 6+7,... from frame1 and the lines 1, 3, 5, 7,... (field-B/odd) of the interlaced frame are lines 1+2, 3+4, 5+6, 7+8,... from frame2.
If frame1=frame2 (nothing moved), then the lines 0, 1, 2, 3,... of the interlaced frame are the lines 0+1, 1+2, 2+3, 3+4,... of frame1(=frame2). That's frame1 filtered with the kernel (1, 1)T (T=transposed), also called box- or mean-filter of dimension 1x2 with an amplification of 2 (=6db).

That was understood. I was commenting on my proposal to stack corresponding lines from successive frames, which cannot work because the time difference between frames must be the time difference between fields. But thanks for explanation, anyway.