A7S 4K sharp/soft?

nyvz

nyvz

Veteran
I was doing some tests comparing my FS700+7Q+ 4k to the A7S+7Q+ 4k and noticed the A7S is way softer than the FS700. I thought maybe my lenses were out of focus for the A7S shots but that doesn't seem to be the case. I will test again, but has anyone else seen this? Granted, the FS700+7Q 4K is crazy sharp maybe partly because of the fast debayer that might also mean it aliases a bit, but in my quick tests it the FS700 4k made the A7S 4k look like 2-3k...

]a7s vs fs700 4k.jpg
 
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Actually I was just comparing the A7S 4k prores file to the FS700's internal AVCHD file and they appear to look almost identical in sharpness and processing... Maybe for some reason the 7Q+ was only getting a 1080p upscale from the A7S? Hmm, must retest I guess?
 
Just shot my first complete videoclip on this system (A7s + Shogun 4K HQ) with the same weird results. Just compared to my Red footage in 4k and seems a blow up from 1080p. Way softer than the red.

Still trying to figure this out too...
 
I don't get this, for me the A7S is sharper than the Red Scarlet (at 4K HD) with the same Zeiss lenses. Partially due to a more conservative OLPF in the Scarlet and partially due to larger pixels and some residue sharpening even at -7 in the A7S.
 
Hmm I just tested shooting a resolution chart in XAVC and in UHD ProRes and the ProRes is clearly sharper... I wonder if it was a processing problem with the older 7Q+ firmware when I did the last test? I should test it in good lighting against the FS700 again since clearly something went wrong last time. It is a bit concerning though that there is any way to end up with a UHD file that seems to just be 1080p uprezzed.
 
According to this test, 4K from the a7S is about as sharp as the GH4, and therefore softer than the NX1 and the BM4K. I didn't find an FS700 4K test on slashcam.de.
 
nyvz said:
Like custom C1/C2 (1 or 2 on the dial)?
Click to expand...

I meant were you in APS-C mode. If you are then 4K is less sharp as it is up sampled. In Full frame mode C mode is actually superior in some ways, less jello and possible less moire.

I find the A7s to be very nice in UHD mode on the O7Q+ how ever I do not like it in Slog mode. I use Cinegamma 4 and an ISO of 200 a lot, this seems less noisy and much quicker to grade. Of course I am set in my ways and always build a PP for each camera that matches a standard look I am used to and I have on many cameras.

Compared to the FS7 the A7s is not anywhere as sharp or noise free. But the A7s is a low light monster. This does not mean I don't light my scenes, just that I can use lower power lights and often just bounce available sources. I wrote about this back in December. My A7s is now my main B-cam to my FS7, they really compliment each other well.

Here is a vid of some early tests before I stopped using Slog in the A7s, I still use Slog2 or 3 in the FS7 as part of my custom PPs.


https://vimeo.com/115198667

Original comments:

I am just starting to dial in the A7s with Shogun and I am comparing to the FS7.
I initially uploaded the 1080 timeline, including 200% blowup. I am now uploading a 4K version as well. I will add that in the next post.
Both cameras were set on Slog2, 3 for the FS7. All Factory settings, both cameras rated at 3200 same lens at f10, 5500K.
Bear in mind Vimeo compresses as well, downloading the 4K version orig upload will give you the best result.
I am not tuning here I am just using factory settings for everything. I think the results speak for themselves. The only grading was bring the blacks to 0 and whites to 100 raise the mids a bit to roughly match shots, and add bit of sat. This was done in FCPX less than 15 sec time grading each shot. If graded in Resolve and sharpening noise suppressed etc. I am sure I could make all these shots look much better. But this is to demonstrate what you start out with.
I hope you find it interesting I do. next I will be in resolve building LUTs.
 
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In my observations, the FS700 4K is sharper than the A7s 4K but not by a huge margin and not enough to be concerned about.

Downsampling a 4K externally recorded ProRes to HD does make it *much* sharper than any internally created HD however.

My workflow for mastering via the A7s is currently

Recording UHD to ProRes
Process in Mercalli, which is the only software that will rebuild rolling shutter jitters, and optionally stabilise it a bit
Denoise in Nuke with internal noise reduction/or the new Neat Video v4 which looks promising (helps with the shadow blotches mostly)
Process the YUV raw data, change colorspace properly (it isn't standard Slog2 but a version of it) and downsample to HD.

That's about the best A7s output in HD you're going to get.

I process YUV manually because there's a little bit more highlight range that way then any of the normal imports, this does vary wildly between platforms and applications though, but in my pipeline it works for me. YMMV

cheers
Paul
 
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