A Guide to Codecs, Gamma & Gamuts for the Sony FS7

The Sony FS7 has proven to be a very successful camera for both Sony and myself! I’ve owned the FS7 for around 2 years now and have used it on a range of productions from Broadcast Documentaries to Promos, Dramas and, not forgetting, Corporate Films too. The form factor, flexibility and picture quality are all exceptional and really lends itself to the type of films I shoot.

Over the last few months I have offered advice on Codecs, Gammas and Gamuts for various productions so thought I’d put my personal preferences and findings down on paper for all to make use of!

PRE-FACE

While you can attain the ultimate picture quality from the FS7 shooting in the XAVC-I codec with SLog3 gamma and SGamut3.Cine gamut at 4K resolution there are many occasion where shooting in this way might not be the best approach. Perhaps you want to extend the record time per GB for longer shoots or want to have footage which requires little colour grading and manipulation in post production. This blog post looks to address these varying factors and I hope to offer my personal preferences with shooting on the Sony FS7.

So let me start and say I believe your choice of Codec, Gamma and Gamut are linked, so please read the blog post in full! 🙂

CODECS

The codec is the format in which the camera records your audio and video onto the XQD memory cards. The two main codecs I use on the FS7 are the XAVC-I and MPEG HD 422 Codecs.

XAVC-I

The XAVC-I codec is my personal preference and is the newer of the two codecs, recording at a higher bitrate than MPEG HD 422, resulting in higher quality pictures. The codec can accommodate HD, UHD & 4K footage along with varying frame rates including the use of S&Q mode.

MPEG HD 422

This is a legacy codec originally used in camera such as the PMW500 offering the ‘broadcast approved’ 50mbps bitrate. This codec is restricted to HD shooting (so no UHD & 4K support) and also doesn’t allow the use of S&Q mode.

Conclusion

So why would you use the MPEG HD 422 codec? For its extended record time; A 64GB XQD card can get you 132 minutes of glorious 1080 25p footage, compared to just 63 minutes in the XAVC-I codec. Obviously this comes at a cost, and that is the picture quality. MPEG HD 422 is both an older codec (therefore less efficient) and a lower bitrate so the picture quality doesn’t stand up to the XAVC-I codec. This said, it was and still is ‘broadcast approved’, so following my advice below with regards to gamma curves you can still make very pretty pictures.

So, if you want extended record time for filming the likes of conferences, where the ultimate picture quality (and flexibility) isn’t necessarily needed, then shooting in the MPEG HD 422 codec is a good option. If you are after the ultimate picture quality the FS7 can offer you, and the ultimate flexibility for the choice of frame sizes, frame rates and gamma choices (coming up), pick the XAVC-I codec.

GAMMA CURVES

With the FS7 we have a massive range of gamma choices, but for me I feel only two of them are worth considering; Sony’s Hypergammas and SLog2/3.

But what is Gamma? 

To keep this post simple, I would describe it as how the camera records the contrast of what lens is seeing… simply how it records the brightest to darkest areas of the picture. Some gamma curves can see into the brightest and darkest areas of the image better than other but at the expense of the final picture looking low contrast. The more you push the extent of what the camera can record, the more work is required in post production in the form of colour grading to make the image look ‘normal’ for a standard TV, computer or mobile device.

SLog2/3

Sony offer two variants of Log on the FS7; SLog2 and SLog3. Both of these gamma curves records the maximum brightness ratio (number of stops) the camera is capable of capturing. This comes at the compromise of requiring colour grading to make the images look ‘normal’. I’d only recommend using this option when there is time and budget to grade the final deliverables. Equally, as the footage requires a large amount of colour grading and manipulation I’d only shoot in the XAVC-I codec for this Gamma choice.

Hypergamma

Sony’s Hypergammas are a compromise between a normal looking picture and capturing an extended brightness range compared to a standard gamma. For me, these are a great option as personally I feel the pictures look great straight out of the camera OR can take some manipulation and colour grading in post to really make the images pop! Shooting in a Hypergamma, compared to Log, is also a little more straight forward too; allowing custom white balancing, WYSIWYG monitoring in both normal and S&Q mode and personally I feel an extended ISO range too, producing cleaner images at higher ISOs compared to shooting SLog2/3 in CINE EI mode.

Conclusions

If you want to take advantage of the extended contrast range of the FS7, and you have time to colour grade your footage, then take advantage of shooting in Log. Personally, I use SLog3 as this is the most recent SLog gamma curve from Sony and offers more flexibility in Gamuet compared to SLog2 (more of that below), shooting in the XAVC-I codec. When shooting SLog3 I tend to find rating the camera at 1000 ISO, and therefore ‘over cooking’ the image by one stop, results in cleaner blacks in post production when you correct for the over exposure.

If you want the ultimate flexibility when on the shoot with the camera, and colour grading isn’t a priority, I’d shoot in a Hypergamma. HG7 (or 8) is a good option when shooting in the XAVC-I codec as this offers the greatest contrast range of all the Hypergammas; personally, I stick with HG7. When shooting in the MPEG HD 422 codec I tend to find it spreads the image a little to thin so I feel HG4 is a better option when shooting in this codec as the extended contrast range is a little smaller but still offer some flexibility over a ‘standard gamma’. It is also great for matching with the Sony A7s as this camera has a comparable Gamma Curve in the form of Cine 1, offering the same contrast range and grey point. Anyway, on both the FS7 and A7s, these Hypergammas need to be ‘under cooked’ to get the most out of it’s contrast range, usually putting normally exposed skin tones around the 55-60% IRE mark.

THE MATRIX & GAMUTS

With both SLog Gammas and Hypergammas we have various options for the camera’s Gamuts and Matrix respectivly, basically the way the camera records colour.

SLog2/3

In CINE EI mode you have the choice of 3 Gamut options; S-Gamut, S-Gamut3 and S-Gamut3.Cine. All of these Gamut options capture more colour information than is displayable on a standard REC709 TV. If you shoot S-Gamut or S-Gamut3 you do require a LUT to bring the colours into line with the REC709 colour space, therefore just using a simple 3 way colour corrector would result in the colours being skewed. Personally I choose S-Gamut3.Cine as this Gamut is the one most closely linked to REC709 colour space and can be manipulated more easily with a 3 way colour corrector. This option is only available when shooting SLog3.

Matrix

When shooting in the Hypergamma options the camera’s matrix is where you can make adjustments to the way the camera captures colour.

Personally I tend to keep it simple and stick to either to the Standard matrix or F55 709 Like, which is slightly more saturated than the Standard matrix.

CONCLUSIONS

I hope this blog post helps get your head around the Codecs, Gammas and Colour options for the FS7. Below I have compiled a little flow chart to help you choose the best (in my opinion) camera setting depending on your shooting requirements.

Codec	Gamma	Gamut/Matrix
XAVC-I	SLog3 HG7 HG4 (Match A7s Cine 1)	S.Gamut3.Cine Gamut Standard/F55 709 Like Matrix Standard Matrix
MPEG 422	HG4	Standard Matrix

ENJOYED THIS BLOG?

Why not check out some of the projects I’ve shot on the Sony FS7…

Gym Shark Spec Commercial – High End Commercial

Shot in UHD, XAVC-I, SLog3/S-Gamut3.Cine

Folio Albums – Corporate Film

Shot in HD, XAVC-I, Slog3/Burnt in LUT

Strata Charity Ball – Event Film

Shot in HD, XAVC-I, HG4/Standard Matrix

Found this blog useful? Why not ‘Buy me a Coffee’ and help keep my blog running! Follow the donate button below.