a7s rolling shutter test please

[squig]

Worse than the 5d2... don't want to move backwards. Do you guys have a measurement for the D90? Maybe it was around 40?

33

I couldn't use it as an A cam but it will certainly work as a B cam.

 

[Cosimo Bullo]

Just saw the D90 measured at 33, so the new Sony is in that territory. We had plenty of problems with the 5d2 at 25!

I'm very excited about the A7s, but it's looking more like a specialty item to me, not nec the do everything small cam.

 

[squig]

Just saw the D90 measured at 33, so the new Sony is in that territory. We had plenty of problems with the 5d2 at 25!

I'm very excited about the A7s, but it's looking more like a specialty item to me, not nec the do everything small cam.

Yeah totally. I had a D90 and I still have a Nex 5n so I know what I'm in for. I'm shooting a scene for my feature in a remote quarry at night and I need to get some wide shots, even for those shots alone it's probably worth getting the A7s, otherwise I'd need to pay at least as much for a white truck, the high ISO IS that good.

 

[Samuel H]

What about this test where the APS-C mode was looking weak compared to the full frame mode?

It is softer, and has aliasing and moire. None of which will matter in the kind of shot that would get ruined by a slow RS.

I will shoot FF most of the time, using a tripod/steadycam/movi-like-thing/shoulder-rig, and maybe 5% of the time I'll switch to APS-C for some shakycam shots. I like my shots steady anyway: on my 5N (29.4ms) I get bothered by shake way before RS becomes an issue.

 

[philiplipetz]

Did i miss a RS measurement in crop mode?

 

[Samuel H]

I don't have a number yet, just an extrapolation: with standard sensor technology, it should be 1.52 times faster than in FF mode, so, around 20ms. It can be even faster if they can do row+column windowing (not common AFAIK), I would be very surprised if it is slower.

edit: I just checked that the GH4 falls exactly where I would expect: 4K reads 2160 lines and has a readout time of 22.5 ms, 1080p reads 1296 lines (2592/2, it skips every other line) and has a readout time of 13.7 ms, which is approximately 22.5*1296/2160. I think 20ms for the a7s+APSC is a reasonably safe bet.

 

[photochris]

I'll go out and shoot the same pole in APS-c mode so you can get an actual measurement.

 

[Samuel H]

So, photochris sent me the APS-C test, and it is basically just as expected: 19.4 ms (I said 20ms but this is well within range, my measurement error can easily be a couple of ms)

That is slightly faster than the 5D3, and actually faster than most other stills cameras

Full table here

 

[photochris]

Just eyeballing it, it clearly looked better, much less skew in the pole that was the test subject.

Chris

 

[eddavid]

The D90 was about 33 ms, the 5DII about 25ms, and the A7s is 30.5ms. I'm frankly a little surprised that Sony deemed that good enough to produce a camera in 2014. If it had been roughly like the 5D III (20ms), I would have been perfectly happy.

Some Sony representatives apparantly said at one of the trade shows that the RS should be tuned to at least match the 5D III in the final production/ firmware version. I guess that was either just to deflect the issue, or perhaps any faster sensor readout turned out to generate to much heat.

I smell a magic latern style hack to turn up that heat !

 

[wallrc]

Well, it's encouraging at least to know that they have *some* control over the rolling shutter via firmware, and that a future tweak to improve it is not impossible.

 

[Samuel H]

You always have some control, specially if you have resolution and sensor size to spare: you can also shoot 4K-FF and then crop 2x, which makes it 15ms

 

[squig]

You always have some control, specially if you have resolution and sensor size to spare: you can also shoot 4K-FF and then crop 2x, which makes it 15ms

How does cropping 4k change the skew angle //// I don't get it :huh:

 

[dfreerider]

How does cropping 4k change the skew angle //// I don't get it :huh:

Kind of confused myself, but I guess that what we are really measuring is the time it takes the sensor to scan from top of the frame to the bottom. If you crop the frame in half, the time it takes the sensor to scan the cropped frame is halved as well. However I don't think it will help the angle of the skew.

But like I said, kind of confused myself.

 

[Samuel H]

Rolling shutter time is how long it takes the sensor to go from the top of the image to the bottom of the image. On the a7s shooting FF, the last line is recorded 30.5ms after the first line was recorded. If you throw away most of the image and use only a small 2x crop from the center, your last line is recorded 15.2ms after your first line was recorded.

The angle is helped because you have to take this into account before shooting, and use a wider lens, and for the same motion you'll have less skew. If you want fast-RS 50mm, you shoot 4K FF with a 25mm and then crop 2x. It actually works, at the expense of resolution and DoF. You can test this yourself using any RS camera.

It's exactly the same principle by which the APS-C mode has faster RS but will require you to use wider lenses.

 

[dfreerider]

Rolling shutter time is how long it takes the sensor to go from the top of the image to the bottom of the image. On the a7s shooting FF, the last line is recorded 30.5ms after the first line was recorded. If you throw away most of the image and use only a small 2x crop from the center, your last line is recorded 15.2ms after your first line was recorded.

The angle is helped because you have to take this into account before shooting, and use a wider lens, and for the same motion you'll have less skew. If you want fast-RS 50mm, you shoot 4K FF with a 25mm and then crop 2x. It actually works, at the expense of resolution and DoF. You can test this yourself using any RS camera.

It's exactly the same principle by which the APS-C mode has faster RS but will require you to use wider lenses.

Yeah, makes sense. I'm wondering if a nex speedboster may actually be useful on the A7s in APS-C mode. It would allow you to get a faster RS while keeping your lenses FF field of view wise. For any kind of handheld stuff this could be useful. Allthough then we are back to moire and aliasing issues again of course.

 

[Samuel H]

the speedbooster works in APS-C mode, somebody tested it on another thread
moire and aliasing won't be an issue for the kind of shots that require a faster RS, they are going to be motion-blurred anyway

 

[squig]

Rolling shutter time is how long it takes the sensor to go from the top of the image to the bottom of the image. On the a7s shooting FF, the last line is recorded 30.5ms after the first line was recorded. If you throw away most of the image and use only a small 2x crop from the center, your last line is recorded 15.2ms after your first line was recorded.

The angle is helped because you have to take this into account before shooting, and use a wider lens, and for the same motion you'll have less skew. If you want fast-RS 50mm, you shoot 4K FF with a 25mm and then crop 2x. It actually works, at the expense of resolution and DoF. You can test this yourself using any RS camera.

It's exactly the same principle by which the APS-C mode has faster RS but will require you to use wider lenses.

Duh... I didn't think about the FOV.

 

[ectobuilder]

Its a typical Sony!

Its a typical Sony!

I've gone back and forth on this thing since NAB. Changing my mind almost everyday. I am beginning to think the cons are outwaying the pros here. It's great looking and a nice piece of tech for sure, but the quirks it comes with is starting to look equality as annoying. I was really excited when it was first announce because it sounded like a hurdle past other cameras limitations and really brought a lot of desired elements together. As usual though, it's a trade off. I know every tool for every job. This particular tool is starting to become clear of what it can and can't do. So far, not pulling the trigger yet.

It's typical Sony to lead with a headline feature only to disappoint in the overall package.

I'd rather have a well balanced camera than a camera great in one thing but be lacking in everything else.

On the other hand the A7S would be more attractive at $1200 and if it had better native lenses.

 

[photochris]

It's typical Sony to lead with a headline feature only to disappoint in the overall package.

I'd rather have a well balanced camera than a camera great in one thing but be lacking in everything else.

The A7s is loaded, it does many things well, and many better anything in its price range IMO.

Its one of 2 FF cameras on the planet that shoot 4k, and shoots more detailed & higher DR 1080p compared to pretty much every other dslr/mirrorless camera available. The highlight and shadow recovery of A7s files is amazing. Plenty of great stuff was shot with the 5d2/3 and this - IMO - completely spanks both of them, except for rolling shutter when compared to the 5d3. But the video is still much sharper and no moire or aliasing. Its also 1/5th the price of the 1dC. Now the picture profiles certainly are challenging with so many adjustments, its not like the 5d where you could make a couple quick adjustments and shoot something nice right out of the box. But it certainly doesn't have the compromises something like a Blackmagic camera has.

Its also a fantastic stills camera, smaller images, but once you move above 3200, the A7s holds details much better than higher MP cameras - even when matched with the A7r or D800. The DR gives images so much depth. Large aperture shots from the A7s are just stunning. Just my opinion.

On the other hand the A7S would be more attractive at $1200 and if it had better native lenses.

This time next year used A7s's will probably be in the $1200 range and there will be another 4-5 lenses including the massive 28-105/4 cine lens. I bought the A7 with a grip and the 28-70 lens for $1700 last month, so the prices come down pretty quick. The FE mount is also the best platform for legacy lenses, since you maintain native FOV and DOF characteristics and pretty much every lens ever made can be adapted. Again my opinion.

Every camera has warts and everyone's needs are different, but for me the A7s ticks more boxes than any other hybrid camera at the moment.