Is it actually blade shape I should be looking at? I appreciate the time Uli spent doing this but would love to see it against a uniform background and without the fan grilles. I'd also like to know the shutter speed/angle.
I had a RED representative reply earlier this month with "I have confirmed with our engineers that the read/reset rate for both EPIC and Scarlet will be the same." when I asked about the rate at which data is pulled from the sensor - but that doesn't look to the the case. The delay looks to my naked eye to be much larger on the Scarlet.
How is rolling shutter measured? Is there a way to determine the # of ms delay?
BTW - what shutter and frame size where you shooting with?
I dunno. On the SX grab, the fan blade on the right looks larger (implying more RS), but the two fan blades on the right look smaller than the ES shot (implying less RS.)
... Is there a more scientific RS test?
I too, really appreciate the side by side comparison Uli. However, I would argue that those 2 images look identical when comparing rolling shutter. Sure the blade on the right side of the fan looks "longer" on the Scarlet pic, but I would point out that the two blades on the left side of the fan are "longer" or "fatter" on the Epic pic. I think this is caused by the angle of fan in relation to the camera. They are not constant. There is a slight difference which I believe is the cause of the false conclusion that the Scarlet is different from the Epic with regards to rolling shutter. Notice the tabs on the outer ring of the fans cage? The Epic example has them against a white out of focus background, while the Scarlet example has them against whatever the darker out of focus portions of the frame are. Either the level of the camera or the level of the fan changed slightly. However, I will perform my own tests in order to confirm my hypothesis. Can someone explain if there is something I am not seeing, or if I am looking at the wrong thing? Maybe some moving image comparisons are in order. Thanks again Uli for posting this example for us to evaluate.
Edit: Mike beat me to it :)
We need a more scientific test. as many pointed out the angle of the fan to each camera is a factor for different results. Other factors include, assuming all other settings are equal (lens, shutter speed, distance, angle, etc...):
- fan speed may not be consistent
- the motor of the fan may not spin in a perfect single axis, meaning the blades could sway a tiny bit closer and farther from camera at random times.
- other factors...??
For those that aren't aware what to look for. Rolling shutter causes skew in objects in motion. So a straight vertical building moving fast across frame, will appear slanted. In this case, a fan blade rotating fast in a circle will be slanted in a circular distortion.
Sorry, was quite dark all day through. Shot at 1/400th, both 4K HD, same lens, the fan is quite constant, I use it for other cam tests too.
Of course this is not scientific, but a relative comparison. I don't think it will by anything noticed by our clients, but it may cause problems when you need 3D camera tracking.
BTW, the blades are same shape, same size, of course – or the fan would destroy itself in seconds…
Wouldn't a better test of this be to pan both cameras quickly?
If I had a double pan head, maybe ;-)
But this test is far more reproducible if you don't have a motorized head.
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