With Sony’s log capable cameras (and most other manufacturers) when you switch between the standard gamma curves and log gamma there is a change in the cameras ISO rating. For example the FS7 is rated at 800 ISO in rec709 but rated at 2000 ISO in log. Why does this change occur and how does it effect the pictures you shoot?
As 709 etc has a limited DR (between around 6 and 10 stops depending on the knee settings) while the sensor itself has a 14 stop range, you only need to take a small part of the sensors full range to produce that smaller range 709 or hypergamma image. That gives the camera manufacturer some freedom to pick the sweetest part of the sensors range. his also gives some leeway as to where you place the base ISO.
I suspect Sony chose 800 ISO for the FS7 and F5 etc as that’s the sensors sweet spot, I certainly don’t think it was an accidental choice.
What is ISO on an electronic camera? ISO is the equivalent sensitivity rating. It isn’t a measure of the cameras actual sensitivity, it is the ISO rating you need to enter into a light meter if you were using an external light meter to get the correct exposure settings. It is the equivalent sensitivity. Remember we can’t change the sensor in these cameras so we can’t actually change the cameras real sensitivity, all we can do is use different amounts of gain or signal amplification to make the pictures brighter or darker.
When you go switch the camera to log you have no choice other than to take everything the sensor offers. It’s a 14 stop sensor and if you want to record 14 stops, then you have to take 100% of the sensors output. The camera manufacturer → continue…
By Noam Kroll
While it’s certainly just a matter of preference, my pick would always be the latter of the two images. It’s so much more interesting to not see everything all at once, and to use DR – or lack of it – to draw the viewer into the image.
To use an analogy, consider shallow depth of field –
There are scenarios where deep DOF will work better (by allowing the viewer to see everything in the image with equal clarity), but more often than not, using selective focus is the better choice as it helps guide the audience to the most important part of the frame. It’s a more human and organic way to interact with an image.
While most filmmakers seem to understand this concept when it comes to depth of field, fewer seem to understand how the same logic applies to dynamic range…
Perhaps it’s the overemphasis on high DR in today’s filmmaking landscape (particularly thanks to marketing efforts by camera manufacturers) that’s led some filmmakers to prioritize the protection of their DR in the color grade above all else. Many are focused on the technical achievement of not losing any highlight or shadow detail, while neglecting the bigger question at play: How does the image make the audience feel?
It’s not uncommon to watch finished films today that appear to be made up of ungraded raw footage. This is often a direct result of filmmakers being so careful with their use of contrast (as a means to avoid losing even a tiny bit of dynamic range), that the final product remains so flat that it could almost look like it’s still in Log color space.
That’s not to say that this is a bad look. There are no right or wrong choices when it comes to your aesthetic… You just have to make sure the choices you’re making are purposeful and ultimately serve your story above all else.
So when it comes to your film, ask yourself – Does an ultra flat image evoke the mood in your audience that you’re looking for?
If so, great. More power to you. But if it isn’t the right look for your film, don’t feel like you need to go down that path just to prove how much dynamic range your camera’s sensor was capable of.
And just for the record, I love high dynamic range sensors. DR is one of the most critical factors for me when buying a camera… And I’ve even written multiple articles on that very topic on this blog.
But I seek out high DR cameras so I have options in post, not because I believe my final image needs to squeeze out as much range as humanly possible.
Assuming I plan to do an extensive color grade, having the maximum amount of DR possible means that I can really fine tune just how much of that DR makes it into my final image.
Even if I end up with crushed shadows and blown out highlights, and even if I could have achieved that look with a camera that only shoots 8 stops of DR, I would still like to have 13 or 14 stops so I can experiment in post.
It’s all about having options.
What it’s not about is preserving every last ounce of dynamic range in the color suite – unless there is a specific creative reason for it.
So as we wrap up, I’ll leave you with this –
Great filmmaking is born out of the unique creative choices that we make. Don’t let camera manufacturers tell you what looks good or what’s cinematic. Listen to your own voice and be your own judge of what is aesthetically pleasing. If that happens to be an ultra-flat look, then that’s great. But it’s just as acceptable to have a low DR final product if that’s what your story needs.
As we all know, high dynamic range is one of the key ingredients needed to achieve a cinematic look.
This of course is because most of us really equate “cinematic” with “filmic” (whether we realize it or not), and images captured on film traditionally have had far more dynamic range than digital footage… With the exception being reversal film, but that’s for another article.
Until cameras like the Arri Alexa came out and proved high DR was possible on digital cameras, any sort of digital cinematography was always associated with low dynamic range, clipped highlights, and a low quality aesthetic.
A lot has changed in the past 5 years or so, and now we can buy cameras for as little as $1000 (see Blackmagic Pocket Cam) that are capable of delivering dynamic range in the same ballpark as what you might expect of film. This has been incredibly liberating for filmmakers on a budget who desperately want to create film-like images but don’t have the budget to shoot on real film.
At the same time, there has been one somewhat unpleasant side effect of this democratization of dynamic range…
With such a premium placed on DR in today’s filmmaking landscape, many filmmakers are afraid to sacrifice dynamic range for style when it comes to the color grade.
This is likely a result of being beaten over the head by camera manufacturers and marketing companies that preach that more dynamic range = more cinematic images.
And I would argue this is only half true…
While I do believe it’s crucial to capture as much DR as possible, I don’t believe it’s necessary to retain all of that DR in the grade. If anything, I think it can be counter productive when the main goal is to make something look “cinematic”.
From:: Noam Kroll