OK, not really very scientific, but I’m busy on some paying projects at the moment and the weather is very changeable so I only had a short window to do this. I’m still exploring the image quality of the FS700. It is very good, of that there is no doubt, but my benchmark right now is the F3. So I just did a very simple side by side test to look at noise and dynamic range. The scene has about an 11 to 12 stop range if you include the specular highlights and reflections off the silver car bonnet and the brightest clouds. If you take the S-Log clip as the reference the clouds are at about +5.5 stops over nominal middle grey and the darkest part of the image, the black stand holding the chart, is about 6 stops under. I wasn’t looking to actually measure anything here, just get a feel for the differences between the cameras.
The cameras were set to 800 ISO for all the clips, so the FS700 had +6db gain applied for all clips while the F3 had +6db applied for the Cinegamma and standard gamma clips and no additional gain in S-Log. Frame rate was 25fps with a 180 degree – 1/50th shutter. The HDSDi out from the cameras was recorded using ProRes 4:2:2 on an Atomos Samurai.
For the S-Log sample I exposed using the DSC Labs S-Log exposure reference chart (which you can see in all the frames) by placing the cameras centre spot meter over the middle grey and aiming for 38%, however my waveform monitors are telling me the mid grey exposure was actually 35% so I’m about a 1/4 stop under (and need to check why I didn’t get 38%). For the Cinegamma 4 tests I used the histogram to keep peak white at about 95% with similar mid range exposure. In fact the mid grey patch on the DSC S-Log chart is around 38-40% on both cameras which is just a touch low for the cinegammas (I normally aim for 42%-45% with cinegammas). Exposure for the standard 709 gamma was established with the histograms trying to get a reasonable balance between clipped highlights and a reasonable mid range. The result is that the standard gamma shots are under exposed by around 1.5 stops, mid grey is only 33% on the F3 and 30% on the FS700. I would normally aim to put middle grey around 45-48% for Sony’s REC-709 compliant gammas. If this shot included a person or face then I would have been forced to either over expose the sky still further or use some fill lighting or a reflector to bring up the foreground. This is typical of the dilemma you get when trying to expose a scene with a greater range than the camera can deal with, do you overexpose the sky to preserve the mid range or underexpose the mid range to keep the sky. Either way something has to suffer.
While not very scientific I think the clips highlight some interesting differences between the two cameras. The most striking difference is the colour. Both cameras were set to preset white at 5600k with their standard colour matrices. White does appear to be white, but the F3 when not in S-Log is clearly more saturated and has a touch more red and a lot less blue that the FS700, so clearly I’m going to have to do some work on the matrix to get these two cameras to match better. Next thing to note is that the Cinegamma curves are quite different. The FS700 curve has more gain in the mid range which results in brighter upper mid range compared to the F3. The dynamic ranges are very similar, I could have exposed the FS700 about a stop lower to gain a little more highlight room, but this would have resulted in some quite dark mid tones and a little loss of shadow detail. In both cases the cinegammas give a quite appreciable increase in dynamic range over REC-709. I would guess at about a 1.5 to 2 stop improvement in dynamic range gained from using Cinegamma 4 over the Sony REC-709 compliant curves + knee. The S-Log clip from the F3 shows the marked increase in dynamic range that you get when using log. The brightest clouds are about 5.5 stops over middle grey with the peak recording level reaching about 89% which means there are around a further 1.5 stops of unused headroom available.
The FS700 is a little noisier than the F3, no surprises here. It’s not hugely noisier and the noise levels at 400 and 800 ISO are perfectly reasonable for a broadcast production. At a push I would use 1600 (+12db) if I had to, but I think for me at least the comfort zone is 400 – 800 ISO (0db and +6db).
The FS700 images appear to lack a little of the crispness of the F3. This may just be because the standard F3 is a little over sharpened (in my opinion). The FS700 pictures look more like the S-Log F3 which has no added image sharpening and in fact in some respects the Cinegamma FS700 looks more like the S-Log F3 than the Cinegamma 4 F3. From what I’ve seen you probably could figure out a very flat log type picture profile for the FS700, but I’m not sure that this would bring any significant benefit over Cinegamma 4. The extra noise in the shadows that you would get if you bring up the low end with some black stretch (black gamma) would likely limit the usefulness of any slight extra latitude gained. However you look at it the FS700 does appear to be able to cope with around 12 stops (maybe a little more) just by using Cinegamma 4, which is about as much as you want with a 8 bit camera anyway.
Interestingly I spotted some moire and aliasing from both cameras. The dreaded roof tiles of the houses opposite (a tough test for many cameras) strike again and the F3 is showing a little coloured moire across the roof tops while the FS700 is showing some aliasing on the grill of the silver car. I’m not concerned by either. Yes it would be nice if it wasn’t there, but I’ve shot hundreds of hours with my F3 and it’s very rare to find any shots that are unusable or problematic due to aliasing.
If you want to download the actual footage please use the link below. The file contains a single clip made up of about 5 seconds each of the FS700 with Cinegamma 4 and standard settings, the F3 with cinegamma 4, standard settings and S-log. The clip is a direct copy of the original ProRes 422 files recorded from the HDSDi outputs of the cameras. 10 bit for the F3 and 8 bit for the FS700. The file size is 150 MB and 10 seconds long in total. Lets hope the file sharing service works as advertised!
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Here are some jpeg frame grabs. Remember you can click on each image to see it larger and once you’ve clicked though to the larger image there should be a link just above it for the full size 1920×1080 original.
Thank you Alister, great comparison. This confirms the impressions I have after comparing FS100 and F3, the colour handling is totally different (especially if using the REC709 Matrix, better to use Standard Matrix as a starting point for tweaking). What strikes me is how similar FS700 is to FS100 in terms of “resolution” and crispiness, I mean the pixel count and the sensors are very different. The F3, as you show, has more “presence” or crispiness (even if I really like what the lack of it does to faces and skins). My guess is that it is a result of use of different cirquitry and A/D-converters in the two different camera line ups. Can you please explain why you can not record 100% of the F3 S-log signal? Why only 89%? Kindest regards/Dennis
You can record the full 104% S-Log signal, but the scene did not have a large enough dynamic range to need to use the full 104%. The F3 cam manage around 13 stops but the seen only had about 11 stops.
I think something that needs further investigation with the FS700 is which gamma is the best to use. Measurements by Adam Wilt and my own experimentation indicate that Cinegamma 4 gives the greatest dynamic range, Adam suggesting in excess 13 stops. Given that this iran 8 bit camera with an 8 bit output, that might be a little excessive. The top and bottom ends of the gamma curve are compressed so the mid range is reasonably linear, but it looks like mid grey sits around 42% so some grading is likely to be needed to get the best results. I think a little further experimentation is needed to look at whether Cinegamma 3 which has slightly less dynamic range might produce a better final image as each stop of exposure will have a little more data allocated to it. It’s all pretty marginal stuff, but then when your trying to extract every last ounce out of a camera, sometimes those extra little bits (and bytes) can be a help.
13 stops without S-log is fantastic. Besides from the small differences you mention, do the Cinegamma characteristics match those of the EX1 and the F3? High tone priority, broadcast safe, low key priority.. etc? Thanks!
S-Log only goes up to 104%. The thinking is that as you will be using a 10 bit recorder the few extra data bits that 104-109 would give you are not necessary. Remember dynamic range is not a function of the signal level, all having a slightly greater recording voltage range does is allow you to use the data bits normally used for superwhites, this helps if your using 8 bit but makes much less of a difference with 10 bit.
13 Stops with only 8 bits, really is pushing the limits of what’s really useful. That’s only 18 shades of grey per stop. Compare that to REC-709 which is about 25-30 bits/grey shades per stop (excluding knee) and you can see that 709 will actually be more tolerant in post production and grading.
Yes, you are absolutely right, the 8 bit recording benefit most from the extra voltage range. And of course, we are talking about small details as well, but I am just curious. So, talking about the F3, what you mean is that S-log only use 104% and that Cinegamma 1 make use of the full video range 109% ?
Yes that’s correct. On all Sony cameras that have S-log it only goes to 104%. I believe it’s to avoid clipping on monitors that can’t show super whites correctly. Cinegamma 1,3 and 4 go to 109%, Cinegamma 4 is 100%.
Does the F3 limit the full internal 109% signal to 104% on SDI outputs?