Personal View site logo
Question on how to expose for greatest dynamic range on GH2
  • I have a few questions.

    How to expose for the best DR in an outdoor scene (beach on a sunny day). Will I get the most DR by trying to preserve as much highlights as possible or the opposite or something else? Or it doesn't matter where I expose and DR will always be the same number of stops and anything above or below the DR range will never be recovered?

    In an indoor scene with some harsh/hot lights and shadows will I get the most DR by clipping the shadows or the highlights or it doesn't matter (DR will always be whatever the number of stops regardless of exposure)?

    Whenever I shoot I see the highlights blown out quicker than the shadows but that's just from what I see. No real scientific evidence.

    Thanks!

  • 27 Replies sorted by
  • Tiffen Ultracon filters can give you a little extra usable DR on the low end by lifting the shadows.

    Where possible, flagging off/diffusing your brightest lights and/or adding some bounced fill to your shadows is really the way to go. You can't always expect the camera to do everything.

  • @producer, you can gain perhaps 1/3-2/3 of a stop with low con filters and get some other issues (flaring f.i.) in the process.

  • Only to a very limited extent.

  • The most of the opinions and procedures described in this topic are quite true.

    But I have a question: doesn't a low contrast or ultra contrast filter solve the dynamic range issue to a great extent, especially of GH2?

  • @jonpais

    Not trying to put you off or anything, I understand why that approach works for you, and the gh3 -/+ adjustments are far more responsive than the gh2, which I use a lot.

    With the gh2, I personally think it´s ok to shoot a little dark in harsh (unalterable) lighting conditions and pull up the shadows a bit, if you have the patience to denoise and regrain afterwards. Will the shadows lack in detail? Sure, but so do shadows in harsh lighting conditions with the naked eye. (IN short, it can be made to look good)

    The main crux is getting pleasant highlight rolloff. With the bmd cine cam I´d never shoot dark (in harsh lighting) because the shadows are not very responsive.

    I think the gh3 behaves sort of similarly to the gh2 except there is a little more headroom for the highlights.. so it should be possible to shoot a little dark and pull up some of the shadows.

  • @Nomad @RRRR I confess I'm a novice. And I don't shoot for production or under controlled lighting conditions. I shoot mostly out of doors, either in shade or on overcast days when the lghting is flat, and on occasion in harsh sunlight. And for me, dialing the settings down produces a pleasing look for strongly lit scenes, and mush for the rest. I reasoned that it would be simpler for me to notch up the contrast a bit for the latter, and when I edit, my clips would be more consistent, therefore easier to apply corrections, etc. Again, perhaps faulty reasoning, I am new at all this! In fact, at the moment, I'm just trying to figure out how to get consistently good exposures! ;)

  • Shoot it flat is not always a good idea with 8 bit cameras. Shoot it as flat as the scene needs is a better approach.

  • @jonpais

    What you are talking about, I think, is very much down to what you are going to do with the footage, what you are shooting for, your level of experience and so on.

    I opted against the gh3 and as such, I have only used it a couple of weeks though there is a flaw in your thinking (which holds true with any digital video cam) and that is if your footage is going towards the same production, and you treat it for disparate conditions, you will have tonnes of different treatments in post for the footage you are producing (to create one look), rather than one particular treatment which will make it possible to create a LUT which will get you to 90-95% of the final look if you are consistent in exposure (and camera handling).

    Obviously, it is equally possible to create one LUT for daylight (outdoors) and one for tungsten shots.. and you might not have an problem with different / inconsistent looks in the same edit.

    Shooting as flat as possible might not be the best thing for the final look you want - so one has to start by thinking about the desired look and then attempt to create and manage a workflow for obtaining it. If you don´t have the possibility to decide on a final look, quite often one has to shoot it "safe" to give as much flexibility in post handling as possible and in those cases - "shoot it flat" holds pretty much true.

    After all, if you are not just after recording some event, you will be interested in shaping / controlling light in some way and that is the level where you can assert the most control on the final image; over some camera specific settings (where you will decide on increments)

  • @balazer I'm new to GH3 & the whole "shoot it flat" stuff, but it occurs to me that those who enjoy grading and shoot with all picture settings at -5 are perhaps mistaken. Because we shoot under a variety of conditions, from extremely harsh to very flat lighting, it seems to me that for ease of editing, color correcting, etc., it would make more sense to change the picture settings to match those conditions. For that reason, I don't buy into the one-size-fits-all mentality.

  • Yes. There's detail in the shadows that you can lift up, but the quantization noise is bad enough that you can't lift very much.

  • balazer have you tried this?

  • @balazar good to know your testing. What patch did you use btw?

  • It is good to question one's assumptions. I had assumed that lower ISO settings have better dynamic range, but then I did a bunch of careful testing. I did not try to measure the total dynamic range in EV. I just compared the exposure points at which highlight and shadow contrast diminished to zero across different settings. Highlights were gauged by looking for flashing on the LCD with Rec Hightlight turned on. Shadows were gauged by boosting the image in playback on my PC.

    ISO (with exposure adjusted to compensate): Highlights are unchanged. Shadow contrast starts to be lost at ISO 2000, with a very gradual decrease at higher ISOs. Dynamic range is essentially equal over ISOs 160 - 1600.

    Contrast: lower contrast settings have more highlight range and more shadow range, but the difference is very small.

    Film mode: Nostalgic mode has more shadow range and less highlight range than Standard mode, but the difference is very small. Total dynamic range would appear to be almost the same in Standard mode and Nostalgic mode.

    .

    Things get more interesting if you look at different parts of the shadow range. For the deepest shadows, 1-2 luminance levels above black in the 0-255 range, the shadow range is deeper, smoother, and with better contrast for ISOs 250, 500, and 1000 than for any of the other ISO settings. ISO 500 was best. But none of these deep shadows look very good when boosted significantly. There just isn't enough granularity in this part of the 8-bit luminance space, and it's too noisy.

    For the somewhat less deep shadows, lower ISOs generally had less noise, though ISOs 250, 500, and 1000 were smoother, with finer gradation and less appearance of banding. As with previous experiments on the ISO noise bug, ISO 320 was slightly less noisy in the shadows than ISO 250, and similarly for ISO 640 and 1250 when the bug is avoided. I did not test with the noise bug induced.

    .

    My take-aways:

    • You can't do much to lift the GH2's deep shadows in post: you quickly run into noise and limited luminance precision.

    • Moderate exposure correction can be performed in post on the larger middle part of the GH2's luminance output range , but this can often be done just as well in the camera, with careful selection of the film mode and the contrast setting.

    • Changing the film mode and contrast setting does little to change the total dynamic range.

    • ISOs 160 - 1250 are essentially equal in quality, except for slightly lower noise at lower ISO settings. I have no hesitation to use ISO 1250 with ETC mode off. With ETC mode on, the picture is good up to ISO 640, and somewhat noisy but still quite usable at ISO 1250.

    Armed with this information, my typical practice will be to strive for good exposure in the camera, and only correct in post when I miss. Deliberate underexposure will be something that I attempt only when there is very important detail in the highlights that is just out of reach, when Nostalgic mode's 1/2 stop boost isn't quite enough.

  • We did a test last year with Xyla charts and the "big three" (Alexa, RED and Sony) and added a 7D (PL modified) and a GH2 to the mix. All with the same glass and identical conditions. While it's subjective when you are still considering a stop "visible" in the noise, the GH2 had 9.5 stops for us, the 7D with tweaked settings about 10.

    The Alexa was the clear winner with 14 to 14.5 stops, the RED showed 11 to 11.5 (without HDRx). The Sony didn't get a final voting, since it didn't have the RAW S-log recording then.

    So, yes, if you need to do a lot of color grading, the BM will be attractive. OTOH, a GHX with more Dr is not really useful without at least 10 bit encoding to give leeway for grading.

  • Have there been measurements of the GH2's dynamic range in video mode?

  • always concentrate on high light area in the shot set them to rite exposure then set artificial aids to improve dark area. Hdr is something which has equal light condition between mid to high low to high and mid to low.

  • Polarizers are massively helpful in harsh lighting, agree.

  • @ipcmlr Minor corrections in post are OK, but exposing too flat and compensating in post will degrade your picture because of the 8 bit limitation. One should try to get as close as possible to the intended result in camera.

    Balazer's explanation is excellent, IMHO.

    You should also read this article, which Vitaliy linked a few days ago: http://theonlinephotographer.typepad.com/the_online_photographer/2012/09/why-iso-isnt-iso.html

  • I find a polariser works well on a sunny day. I have used grad ND's in the past but found them to introduce banding in the sky. Obviously the grad is only useful in a static situation. I find Cinema to hold onto highlights a little better too.

    This problem is not unique to the GH2. It's fundamental to shooting with pretty much any video camera, up until the Alexa and BMCC. Even using a RED camera a DP I worked with was still stacking Grad's and ND in front of the lens to bring detail back into the sky.

  • BMCC is the solution if you have the money and can transport more gear/rig, 13 fstops DR.

    Another solution most GH2 owners usually hate is to use a Canon camera like T3i

    T3i have lower resolution and moire/aliasing problems, but: it has one more fstop over the highlights in default settings over GH2. it has HTP highlight tone priority which brings another fstop. It has some custom picture styles which brings less clipping in highlight and lift the shadows (lightform, cinema ps, marvel, superflat and many others), also it has the magic lantern hdr video which allows incredible 5EV increase in DR, and the mosaic engineering optical filter can correct moire/aliasing. (do a research about all of this and you will start to consider it)

    Resolution is not everything!

  • @balazar @rrrr I don't mind correcting in post so I do the flattest picture profile as possible normally. Is iso 160 the gh2's native iso?

  • Not sure why post work would be something to shun if it´s an important shot but; one key issue with the gh2 is that you always have less DR above 50%, so you definately need to let go of something to get a good exposure in harsh lighting conditions. Key is what you can afford to lose! Always, always use the histogram.

    Smooth or Standard are the general go to settings IMO but you might consider Nostalgic if you are ok with the added grain and the added lift. Not good for highlight roll-off but you might be able to counter it with exposing for highlights.

  • This is exactly the problem I've been working on this week.

    The camera's dynamic range is a function of the camera and its settings. It has nothing to do with the image or the exposure. You want to expose properly, and then balance the overexposure against the underexposure.

    Here's my procedure, which assumes you are not going to grade. It's a work in progress.

    1. Set the contrast to 0. Setting the contrast to -2 increases the dynamic range a tiny bit, but the larger effect of decreasing the contrast setting is a change in the response curve that decreases the contrast in the biggest part of the camera's response curve, and increases it slightly at the ends. If you choose -2 just to gain a tiny bit of dynamic range even when the picture looks better with a higher contrast setting, you are pretty much ensuring that you will need to manipulate the resulting picture in post processing to make it look right.

    2. Set the film mode to Standard. Nostalgic mode supposedly gives a tiny boost in dynamic range. I wouldn't choose Nostalgic just for the sake of gaining dynamic range.

    3. Decide what your subject is, and expose it so that it looks right and is positioned somewhere in the middle 2/3 of the camera's output range. If you can't decide or you just say that everything is your subject, you're likely to expose nothing correctly.

    4. Adjust the contrast as necessary to make the image look best.

    5. Decide what's worse: the underexposed areas, or the overexposed areas. You can see the magnitude of the underexposure and the overexposure by adjusting the exposure up and down while you watch the histogram. You can also turn on Rec Highlight in the Motion Picture menu, to get flashing of the overexposed areas.

    If the overexposure is just bad as the underexposure, you're done. There's nothing you can do to improve the situation, short of re-evaluating the badness of the underexposure and overexposure, or buying a new camera.

    If the underexposed areas are worse, set the film mode to Cinema, and increase the exposure or the ISO setting by half a stop or so until your subject is exposed correctly again. Cinema mode lowers the camera's response for the middle 2/3 or so of its dynamic range, which means after adjusting the exposure to compensate, you have less highlight range and more shadow range. The highlight range will be less compressed (have more contrast), and the shadow range will be more compressed (have less contrast).

    If the overexposed areas are worse, set the film mode to Nostalgic, and decrease the exposure or the IS setting by half a stop or so until your subject is exposed correctly again. Nostalgic mode increases the camera's response for the middle 2/3 or so of its dynamic range, which means after adjusting the exposure to compensate, you have more highlight range and less shadow range. The highlight range will be more compressed (have less contrast), and the shadow range will be less compressed (have more contrast). Nostalgic mode affects the saturation and color balance, so compensate by setting the saturation to +2, and adjust the white balance about 6 notches to the right towards blue, and 2 notches up towards green. (or as necessary to make the picture look right and match the white balance of Standard mode) You'll still need to boost the saturation a bit in post to make the image match Standard mode.

    If you couldn't decide, try it both ways. You can program C1 and C2 with Cinema and Nostalgic, including the color correction for Nostalgic, and different ISO settings. Don't forget to adjust the exposure as you flip between C1 and C2, if you're not using different ISO settings.

    Note that there's only about half a stop difference between Standard and Nostalgic, and Standard and Cinema. It may not be worth the hassle to gain just half a stop of additional range in the highlights or shadows.

    .

    There were good tips about using a graduated neutral density filter and/or a polarizing filter. A polarizing filter will bring down a bright sky.

  • @ipcmlr Sometimes a polarising filter can help you lose just the highlights.