Dynamic range, gamma.

F

ffureel

New member
So I know this is the GH1 forum, I just recently got a GF1 though and am sure this could be answered by you GH1 users. The software is probably pretty similar.

Now I am used to RAW photography, exposing for highlights then ligtening the shadows/ gamma to reveal a more natural dynamic range with lower contrast and shadow detail not crushed.

Started doing some video with this camera and obviously with the lack of raw video function I am having to try and replicate what I do with raw photography in the camera for the baked videos.

I am struggling!

As far as I can see the nostalgic film mode is the lowest contrast, with the shadows opened up the most. Have set that mode down to -2 on all the parameters. Unfortunately it seems that the gamma is just too dark still, with the histogram bunched on the left if exposing for the higlights.

I know that is what happens to the histogram if underexposing the scene for the highlights, what I want though is to be able to brighten the gamma before the file is outputted so that the blacks are not crushed and detailless. So that the shadow details are pushed up the histogram and usable.

Is this even possible, if not is quite limiting.

What I want is just a really flat image with as much range as the sensor can output in a semi "RAW" state as I can manage.

A bit like the superflat profile you can use on the Canon 5Dii if you have seen it? Anyway of creating custom film modes on a computer similar to the Canon?
 
I'm surprised no one has responded yet. I guess many DVXUser regulars are enjoying their holiday vacation...away from a computer!

I think you have to consider the video capabilities of the GH1 (or any Video DSLR) in a different way than their still capabilities. It requires thinking differently. The "expose for the highlights" approach you have taken with stills works very well when you have a higher dynamic range and the flexibility of RAW data, but this methodology isn't practical with the GH1's video. The AVCHD codec of the camera has a lower dynamic range and much less flexibility than RAW because of compression artifacts and because the "look" is baked in already. So underexposing, like you would for RAW stills, then pushing up the shadows is going to yield ugly artifacts that I know you don't want. Such is the limitation of this otherwise fantastic camera.

That being said, there are ways that can help you get a more "flat" look.
The consensus from GH1 owners is that the "Smooth" film mode has the flattest gamma, thus bringing the most detail into the shadows. Also, setting the Contrast to minus 2 (which I think you've already done), will help.

Other things that might help are ideas borrowed from SD video camera tricks to increase dynamic range:
1) Low Con filters for the lens. These filters (Tiffen has several kinds) spread light into the shadows and give you a flatter image.

2) Using a polarizer in outdoor shots will cut glare, and thereby allow you to have a hotter exposure before clipping highlights. Thus, your shadows get exposed at a higher level.

The only other suggestion I have is to just think conceptually different when shooting video on the GH1 vs. shooting stills.
Until something like the Scarlet camera comes out, which will allow us to shoot in RAW, you just have to think of this as a different kind of tool. The GH1's weakness is in the deep shadows, just above pure black. That's where the ugliness lives...even in well-exposed shots. What many people are doing (myself included) to combat this, is the exact opposite of how you are shooting stills. We expose TO THE RIGHT. We OVEREXPOSE a touch so that we can bury that noise down into the blacks. You MAY clip something using this method. You just have to decide if it's acceptable or not.

In controlled environments...with movie lighting, etc., you can have your cake and eat it too. You can overexpose a touch without clipping anything (by applying careful lighting ratios), and still have a nice, low contrast image.

But outdoors, in the uncontrolled real world, the GH1's video capability is just different than its still capability.

That's why many of us are waiting for the Scarlet. :-)
In the meantime, the GH1 kicks butt, just in its own more humble way.
 
Hey,

Thanks so much!

What you are saying is probably all there is to know, very helpful. It all makes sense.

I guess the only last thing is... Is it possible to create custom film presets on the computer, to upload to the camera? Custom curves. The included film modes are nothing what I like to see and as the files are set in stone I would like a little more control before hand!

Please someone say yes! :)
 
Sadly, no. There's no way to upload custom curves to the GH1. The Film Modes are rather coarse. What type of scenes do you shoot most often? Is there any way of controlling the highlights by using a fader ND filter?
Oh, and another thing I've discovered is that the LENS you use has a huge impact on contrast. The kit lens is really contrasty (which I like). But I have an old Canon 50mm f1.2 that is very low contrast and really creates milky shadows. I come from a video background and am just learning how much the LENS is a deciding factor of an image's quality. Nikon lenses seem to be contrastier than Canon lenses. At least in my experience. Older lenses have less anti-flare coatings and tend to be more low-contrast. You should check these out because they're usually cheaper than more modern lenses. I'd seriously give it a try because a lens like that would squeeze the highlights and shadows into a more desirable range for you, and you wouldn't have to fiddle with the curves and risk getting ugly noise and artifacts.
So one suggestion would be to find a lens that may do the trick optically as opposed to the cameras curves.
 
When I was testing various Pro mist filters I discovered that it will compress the dynamic range, bringing up the shadows and bringing down the highlights. It also helps with the 'edgy' look the camera sometimes has.

Ffureel- I think what you really need is lighting. A bounce to fill the shadows. A silk to soften the highlights. You need to bring your contrast ratio closer together. I found that the GH1 really liked to be exposed in the upper half of its range, which equates to about 3-5 stops of latitude out of the full 7-8ish that it can see. I don't know if the GF1 is the same, but probably close.
 
Yes, Black Pro Mist filters will spread the light around and make for a nice low contrast image. The problem is that it's primarily a diffusion filter and it can create a soft focus effect, which is great if that's what you're after. But the softness around edges may not be desirable if you just want low contrast. But yes, that's a possibility.
Tim Joy has perfectly valid points about using lighting. This is the tried and true method of manipulating the real world to fit into the limited dynamic range of any camera (even 35mm film). But I'm not sure what our gentleman who started this thread shoots. If he shoots nature and wide shots in the mountains, then lighting will be of no use. :-)
I once was at a scenic overlook at night, and saw a guy taking a picture of mountains. His first shot came out too dark, so he tried again using the flash. Didn't help. :-)
 
dvbrother said:
I once was at a scenic overlook at night, and saw a guy taking a picture of mountains. His first shot came out too dark, so he tried again using the flash. Didn't help. :-)
Click to expand...

In one of the showings that I attended of Andy Warhola's "Dracula"(1974), some joker was taking flash pictures of the screen image... (that is even in the olden days there were idiots with cameras...)
 
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