7D Built-In Exposure and Focus Aids for Video?

[Brian Luce]

Originally Posted by Jerry Porter

Keith,
I don't know if you know this, forgive me if this seems very basic to you. But, on the kit lens after you focus, if you change your zoom at all the lens is out of focus again. On the lower end lenses I guess Canon figured (and everyone else) that everyone would use auto focus. Eliminating the need for the Parfocal lenses.

One thing I don't get about the 7d is why there's no need/ability to backfocus. What's the deal on that? And if we can't backfocus, why should we trust focusing at tele then zooming out for appropriate framing? Focus will be off right?

[Jerry Porter]

Depends on the lens just like your typical pro video camera. With the right lens you can back focus. With the kit lens just like most handy cams there is no back focus... You are dependent on auto focus. It's not the camera it's the lens that is on the camera.

[Roger Shealy]

What I find works is to turn on the histogram function for still pictures, which shows the histogram with the still image review (I have upped playback time to 4 seconds). I just click a picture before starting a video to look at the histogram. I also turn on the function that makes overexposed areas blink on the still-picture review screen, which is somewhat similar to zebra.

I find that if I use the 7D LiveView as a monitor (without the histogram function above), it tends to overexpose slightly, so I typically close it down a little more than the display would suggest to get the exposure I like. I'd like to get a zebra function on this thing!

[Keith Moreau]

Hi Roger

What's the advantage of taking a picture and using playback as opposed to just being in still mode, hitting the 'info' button until you see the histogram, and then switching over to the video mode and taking the video?

[Brian Luce]

Originally Posted by Jerry Porter

Depends on the lens just like your typical pro video camera. With the right lens you can back focus. With the kit lens just like most handy cams there is no back focus... You are dependent on auto focus. It's not the camera it's the lens that is on the camera.

There's a way to back focus the 7d?

[David Chapman]

I don't know of any photo lenses that allow for back focusing. You have to remember, these aren't video lenses where you would normally need to back focus at all to pull off a push in or pull. And, of course, there would be no back focus on the body. It's the lens that has a back focus.

[Roger Shealy]

Originally Posted by Keith Moreau

Hi Roger

What's the advantage of taking a picture and using playback as opposed to just being in still mode, hitting the 'info' button until you see the histogram, and then switching over to the video mode and taking the video?

Keith,

I'm able to get a histogram in movie mode with a single button press (shutter), which is very fast. I don't have to press play or switch back an forth from still to movie or anything. After the shutter button is pressed in movie mode the camera "reviews" the still image taken with histogram automatically, if you have selected it to display histogram during review in menu options. I have it set up so that after any still picture is taken in any mode, the display shows the picture on the left, histogram on the right for 4 seconds before reverting back to whatever capture mode I started in. Also if something starts to happen on the scene I can just press the "start" button and the camera instantly aborts the image review and starts capturing video. I find this the most nimble way to get exposure feedback on the camera in its current configuration but I'd prefer to have Zebra or the histogram live on the LCD at all times.

As I read you response I took out my camera, put it in still mode, and pressed "info" several times but a histogram never appeared without taking a picture. I'd like to use that feature for stills if I can figure out how to get it hold on the histogram. Time to go back to the manual!

[Jerry Porter]

Originally Posted by David Chapman

I don't know of any photo lenses that allow for back focusing. You have to remember, these aren't video lenses where you would normally need to back focus at all to pull off a push in or pull. And, of course, there would be no back focus on the body. It's the lens that has a back focus.

Parfocal lenses stay in focus all the way through the zoom range of the lens.

[Keith Moreau]

Originally Posted by Roger Shealy

I have it set up so that after any still picture is taken in any mode, the display shows the picture on the left, histogram on the right for 4 seconds before reverting back to whatever capture mode I started in.

Roger, you have to have the Exposure simulation On (Camera setting screen 4, 4th item)for the histogram to be available after pressing the "Info" button.)

Thanks for the explanation. It sounds like a good mode. I had to fiddle with it to get the histogram to show up. Just like the live mode, you have to hit the info button a few times to get the right information set to display during the review period. Once it's set, it's sticky. I was trying for a while and nothing ever showed up until I re-read the manual.

However, though it's useful, and I'll have to use it real world situations, I think I prefer to check out the histogram in still mode first, in live mode and adjust the histogram for proper exposure real time, using ISO, aperture, shutter speed, and Fader ND, then switch over to movie mode once I'm satisfied. I chose the RGB histogram, as I like to see the relative levels of each color to see if I'm too hot or dark on a particular color. It's a histogram mode I wish my Sony EX1 camcorder had (it's just total brightness histogram). With your method I'd have to make a change, take a picture, make another change, take a picture, which could be time consuming. With my method I can make changes real time, then flip over.

Your mode, though, does have usefulness I think it would good if I'm in video mode and I just want to do a quick sanity check. Thanks for the hint! Keep them coming!

[Roger Shealy]

Keith,

Let's keep building on these ideas. I can see a use for both. I'm going to try using the RGB Histogram, which I have no experience using. It sounds very useful though.

Thanks for your explanation.

[Michael Maier]

Originally Posted by Charles Papert

There are a few ways to judge focus and exposure accurately before you roll; you can take a still and evaluate the histogram,

I find the histogram only useful to tell you if you are either clipping your blacks or whites, but not a real useful exposure tool. It for example won't tell you if you subject is correctly exposed at key. Also, in a low key scene it's close to useless because it will tell you most of the scene is dark, because it is and you will be probably clipping some blacks anyways. So I don't find much use for it besides black and white clip check. If you expose a scene to get a good reading in the histogram the scene will be boring and flat.

For white clipping is really easy. Just use highlight alert ON.

Originally Posted by Charles Papert

and you can magnify the focus to make sure your subject is sharp.

Yes, I don't find focusing on the 7D hard at all. I just use the focus magnification function in the camera. It works great. I don't get when people complain about the lack of focus assist. You don't really need it.

Originally Posted by Charles Papert

Using a traditional light meter with a DSLR is in my opinion pretty dicey, particularly when you are working in low light levels. The sensitivity of these cameras is such that a face metered virtually off the bottom of the meter at .7 can look pretty nice even when exposed at 2.8. The only times I use my meters on digital shoots any more is to pre-light a set.

Yes, this is true. But I find it useful to set my key. If I set the ISO to 320 or 640 and the lens to 2.8 and I get a 2.8 reading for my key on my meter set to the same ISO I normally get skins at 60 IRE which seems to be a good range for the 7D. Also like using a meter for setting contrast ratios.

[Charles Papert]

I don't really use histograms much myself either, but I wouldn't agree that getting a "good reading" in the histogram will result in a boring or flat image. This may be true if you are working with a predominantly dark scene for instance, you wouldn't want to drive the values up to the middle arbitrarily, but if the frame contains a full range of values it will return a full-looking histogram without resulting in a flat image. Shifting exposure will result in the histogram moving right and left; adjusting contrast or dynamic range would appear to squeeze or unsqueeze the histogram towards the center.

Focus magnification is only useful when the subject or camera is not moving, before the shot. If either happens (as things tend to when shooting motion pictures!), most will be pulling focus by eye and as I said earlier, on longer lenses and open apertures, this is not easy even for seasoned veterans.

[Robert Sanders]

This is exactly the method I've started using on my 7D as well. Pretty reliable.

[Michael Maier]

Originally Posted by Charles Papert

I don't really use histograms much myself either, but I wouldn't agree that getting a "good reading" in the histogram will result in a boring or flat image. This may be true if you are working with a predominantly dark scene for instance, you wouldn't want to drive the values up to the middle arbitrarily, but if the frame contains a full range of values it will return a full-looking histogram without resulting in a flat image.

Sure. But you can't really use it to expose your scene. As in it will not tell if your actor is too dark or not, it will not tell you if the wall behind the subject is exposed as you would like it to be for the mood etc. It's not really an exposure tool in my opinion. Rather a very rough guide that will tell you if you are clipping your dynamic range. Besides that I don't see any use for a histogram. If all I had on set was a histogram to expose, and no monitor, no waveform and no meter, I don't know how I could expose correctly. Now if all I have is a light meter, I can expose close enough without looking at the LCD or at the histogram or even waveform.

Originally Posted by Charles Papert

Shifting exposure will result in the histogram moving right and left; adjusting contrast or dynamic range would appear to squeeze or unsqueeze the histogram towards the center.

Not sure I follow here. Could you elaborate?

Originally Posted by Charles Papert

Focus magnification is only useful when the subject or camera is not moving, before the shot. If either happens (as things tend to when shooting motion pictures!), most will be pulling focus by eye and as I said earlier, on longer lenses and open apertures, this is not easy even for seasoned veterans.

Oh yes, definitely. I was just talking about setting the focus rather than pulling focus. For setting the focus on the 7D I don't miss the EX1's focus assist at all. Now pulling focus you do have to pull by feel or by eye as you can't trust distance marks on still lenses.

[Brian Luce]

Originally Posted by Michael Maier

I find the histogram only useful to tell you if you are either clipping your blacks or whites, but not a real useful exposure tool.

What method/tools are you using to set exposure?