The traditional degree of motion blur, broadly consistent with what the eye normally experiences, is obtained by using around 1/50 sec shutter (no problem in practice for shutter speeds 1/48-1/60). What shutter setting (mode /value combination) can best achieve this for different shooting modes, e.g. 25p, 50i, 50p ? I am no expert on this but from my web-search I assume the following:
- For progressive modes around 25-30p, where light level allows, use Shutter On.
- But for double-rate progressive (50p-60p), use shutter-off.
- For interlaced modes or double-rate progressive or for low light situations, use Shutter Off.
- In interlaced modes, Shutter Off is equivalent to 1/50 or 1/60 (depending if 50i or 60i)
- Warning about Angles: in Interlaced modes, “180 shutter” acts more like a 135 shutter.
- The “Angles” option is really aimed at film veterans, who by definition only use progressive.
On Sony EX3, wondered what frame-rate was involved when shooting 50i. In an attempt to gain suggestions if not evidence as to what is going on, I naively tried some experiments (on a white-balanced white sheet at IRE’s below).
- “Naively” because such results are fairly useless without knowledge of the camera’s sensor and digital signal processing.
- The relative levels were not much affected by choice of Gamma curves, e.g. the very-different STD1 or CINE4. The absolute levels were of course affected, so when switching between gamma curves, I re-adjusted the iris to give 60% IRE at 720p50, my chosen reference-mode.
Results:
- Shutter at None (360 degrees)
- 720p50: 60%
- 1080p25: 70%
- 1080i50: 70%
- 720p25: 80%
- Shutter at 1/60:
- 1080p25: 50%
- 720p25: 60%
- 720p50: 60%
- 1080i50: 69%
- Shutter settings at 1080i50, CINE4:
- None (360 degrees) 70%
- Speed 1/60: 65%
- Speed 1/100: 50%
- Speed 1/125: 45%
- Angle 180 degrees: 50%
- Angle 90 degrees: 35%
Confused, so did some web-searching:
- [http://www.dvxuser.com/V6/showthread.php?217123-Comparison-GH1-amp-EX3-frame-grabs/page2]:
- They’re a full stop more sensitive in 50i than they are in 25p. 400 ISO in 1080/25p, 800 ISO in 1080/50i.
- … higher sensitivity in 50i mode might be (because) in interlaced mode the line (might be being) read as sum of two neighbouring lines.
- “rating” the camera as to its base sensitivity, it is approximately 400 ISO when in 1080p mode, 500 when in 720p mode, and 800 when in 1080i mode. Not talking about an adjustment, just about where it defaults at when at 0dB.
- [http://www.dvinfo.net/forum/sony-xdcam-ex-cinealta/485512-how-do-i-set-1-50-sec-1080-50i.html]
- For 1/50th shutter speed in 50i, just turn the shutter off. (Doug Jensen, Vortex Media)
- [http://www.dvinfo.net/forum/sony-xdcam-ex-cinealta/484894-shutter-off.html]
- As I pretty well always shoot 50i I almost always have the shutter Off as this is the only way to get the correct shutter speed of 1/50th Sec
- Shutter off for low light situations or when shooting interlaced (as shutter off is 1/50 or 1/60)
- If shooting 25p, 1/25 (shutter off) is a little low and most motion will blur. If using 50p you’ll be OK in most situations with it off.
- Usually, if shooting progressive, I shoot 1/50. It gives the best balance of motion and detail on the captured image.
- Doug Jensen: (when shooting progressive – he doesn’t tend to shoot interlaced) I never turn the shutter off unless I’m in a very dark location and there’s very little motion
- [http://www.dvinfo.net/forum/sony-hvr-z1-hdr-fx1/488825-anyone-shoots-1-100-shutter.html]
- Perrone Ford
- I put my EX1 on a tripod, pointed it at a light source, and set the iris so that the center box indicator read at “100”. The camera was set to 1/60 shutter at 1080/30p.
- I changed to 1080/60i keeping the 1/60th shutter and there was no variation in the light level.
- I changed the shutter to “angle” and selected 180 degrees. The light level dropped to “83”.
- I turned the shutter off, corresponding to a 360 degree shutter, and the light level was 100% again.
- So it appears that if you are using “shutter angle” and keeping it constant, that exposure does in fact change when going between progressive and interlaced modes. However, if a specific shutter SPEED is selected, then changing between interlaced and the companion progressive mode, then the exposure is NOT affected.
- Obviously, this would indicate that the 180 degree shutter is acting differently. A 1080/30p at 1/60th shutter gives the same exposure as 1080/30p with a 180 degree shutter. As one would expect.
- Doing the same with interlaced brings different results. A 1080/60i with a 180 shutter is darker than a 1080/60i with a 1/60th shutter. The difference was exactly 1 stop. In my case a difference betewen F8 and F5.6.
- So there you have it. A 180 shutter in interlaced mode is NOT truly a 180 shutter but in fact closer to a 135 shutter.
- Perrone Ford
- [http://www.dvinfo.net/forum/sony-xdcam-ex-cinealta/488921-angle-setting-vs-shutter-speed-interlaced-mode-try-test.html]
- …the shutter angle notion, brought from the film domain, only really applies to progressive video. (Piotr Wozniacki)