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In praise of AUTO.... for RAW stills


hyalinejim
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Today I grabbed my DSLR and went for a short walk around the neighbourhood to take some pics. I wanted to get some shots to test a film look DCP profile I've been working on. As part of my research for this I discovered that most contemporary DSLRs deliberately underexpose when using in-camera metering. This is because for most sensors there aren't actually that many stops between middle grey and totally blown out. For example, my 5D3 will clip at around 3.3 stops above middle grey. I know this because if I shoot a white sheet of paper at 1/3 stop increments and examine the linear RAW values, the exposure that gives me 18% of the maximum RAW value is around 3.3 stops below the one that clips... and that, by definition, is middle grey.

However, this leaves very little room in the highlights. The DR of the 5D3 is around 11.5 stops. So there's three and a bit above middle grey, and around eight below. If you were to meter correctly, you would be very much in danger of blowing out highlights. To help combat this, it appears that most camera manufacturers use 12% grey as the basis for metering. The effect of this is to provide an extra stop or so of highlight headroom. And in fact, this is borne out by checking values in ACR, where actual 18% grey sits at around 185 and 12% grey sits at around 119 (the given RGB number for middle grey in a 2.2 gamma).

Anyway, that's all very interesting or very dull, depending on your point of view. But for some reason it inspired me to shoot on auto exposure on my walk. Even though I normally think of manual exposure control as being the absolute best, I was now considering that Canon have probably tested this a lot and perhaps auto isn't so bad. So I put the camera on aperture priority with auto ISO and started snapping. At first I was kind of worried as I could immediately see two things happening that I would have rectified straight away if I had been shooting manual:

  • Low contrast shots were looking a bit underexposed (I would normally ETTR in these situations to minimise noise)
  • In high contrast scenes some sky was getting blown out (I would normally protect highlights as much as I can)

However, I just went with it. When I got back to my computer I also did something that I never usually do and that was to click the "Auto" button on the ACR exposure tab. I was really surprised with how well everything turned out. ACR's best guess did a great job at expanding or contracting shadows and highlights automatically. All I had to do was tweak overall exposure, and sometimes highlights or blacks as well. Here are some of the results:

MHM_0691.thumb.jpg.570c8624c16e0dd094690bdeaf49a779.jpgMHM_0690.thumb.jpg.69e726dd73e38495ac41e61437ee9576.jpgMHM_0689.thumb.jpg.7113e2548b5941d83f831b05beb85505.jpgMHM_0687.thumb.jpg.233c3c6d1763aa9d2eb83279ecc3bdc4.jpgMHM_0681.thumb.jpg.5a0731ba314683530d8a3c28f07210b9.jpgMHM_0679.thumb.jpg.c0775d8fac4f0c929c8f07258d255a55.jpgMHM_0678.thumb.jpg.a5eff2b2a5d0667365792a98ff43293e.jpgMHM_0675.thumb.jpg.cdd17330f11a7dd19796ee99bc3cfdaa.jpgMHM_0670.thumb.jpg.fef01e511a8f80bcd68193f30c1f5044.jpgMHM_0666.thumb.jpg.41bf8eb089cb72d87d79db53c4f2271a.jpgMHM_0658.thumb.jpg.91bd6eebe15784f815972197e04d7ff2.jpgMHM_0655.thumb.jpg.13f99d3fac133b4f070d2d4c84284caf.jpg

Are there clipped highlights and crushed blacks? Absolutely. But the pics still look good.

Now, I don't know if I would shoot this way for a client. However, I've got to say that it was such a blessed relief to not be constantly chimping the histogram and re-taking shots to get the ideal exposure. And it was also a very good feeling to get the processing done in two or three clicks. It made both shooting and processing a lot more fun.

Who knows, maybe I'm ready for auto white balance next!

 

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One of the reasons Canon is King is that their Auto functions work really well.

I know this post is about Raw stills but I’ve even shot with Shutter priority and ML Raw... with surprisingly okay results.

I think if I had the time to really test it... Shutter Priority, +2-3 stops, in conjunction with AEL Hold, one push AF and an IS lens... the 5D3 becomes a P&S cinema camera.

Btw, nice images.

 

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7 minutes ago, mercer said:

One of the reasons Canon is King is that their Auto functions work really well.

When I'm on holidays I bring a Canon P&S and shoot on Auto and everything looks great. With my DSLR, on the other hand, I was always trying to ETTR as a matter of principle. Yes, it will ultimately lead to a cleaner image but the whole process of taking a shot, checking the histogram, and maybe taking another version of the same shot with slightly different settings, and then maybe again... all this means you're staring at your camera LCD and fiddling with settings.

Recently I had a go at shooting on film, and followed Kirk Mastin's excellent guide for those starting out with film. He gives "set it and forget it" settings for shooting in daylight. It was such a pleasure to just shoot through the viewfinder with no image to review, no exposure tweaks necessary. I was looking at the world and not looking at the back of my camera. So if auto exposure for digital can really be trusted, then shooting becomes a whole lot more pleasurable.

 

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Welcome to my world :)  When I read people talking about getting 14 stops of DR with a camera, in video mode no less, I can only roll my eyes.  Nikon/Sony cameras can get sort of close to 14 stops at ISO 100, but nowhere near at ISO 400/800 say (which is where most video is shot) 

To extend what you're saying.  Even if you ignore the camera's suggested exposure, which I agree, is tweaked according to what mode you're in (unlike what a light meter would say) , you have to consider the sensitivity as pixel exposure decreases as you go from brightest to lowest light.   So if your middle gray, or wherever the sensor can most accurately read light, is moved up or down, it effects the NOISE 2 stops below it.  That is, if you you expose to avoid clipping you may add noise below the image.  If you clip, you may get better saturation (less noise) below--AT ANY ISO, because again, ISO just considers your center exposure.  

Cameras today are truly marvels.  That said, it's still very difficult, for me at least, to really nail exposure.  It's an art, for sure.  Getting a really good exposure, both in setting up lights, and setting the camera up, is no trivial matter.   I believe the best photographers really SWEAT those details--getting the center 6 stops in the optimum range.

Like Andrew's latest video.  The way the lights were blowing out drove me a bit nuts.  I wonder, why can't the camera just figure that out?  It has a computer in it ;)  But it can't.   To get the image Andrew really wants, I assume, he'd have to replace all those practicals with low watt bulbs and then bring up the room light to the right ambient level for the camera.   The camera, any camera, is really the least of one's problems ;) 

So when I read people saying they want 10bit, or LOG gammas, I think, I have enough trouble getting 8bit normal gammas working well!  I mean think about it, why should we have to set a LOG profile and all those parameters.  Why can't the camera analyze the scene and give us some options?  Maybe one day.

For now, I agree with your last post.  You either A) sweat the exposure if you're looking for a certain level of color fidelity or B) put it on Auto and focus on composition.  Doing both at the same time.  I can't do it.  Not even close.

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19 hours ago, hyalinejim said:

However, this leaves very little room in the highlights. The DR of the 5D3 is around 11.5 stops. So there's three and a bit above middle grey, and around eight below. If you were to meter correctly, you would be very much in danger of blowing out highlights. To help combat this, it appears that most camera manufacturers use 12% grey as the basis for metering. The effect of this is to provide an extra stop or so of highlight headroom. And in fact, this is borne out by checking values in ACR, where actual 18% grey sits at around 185 and 12% grey sits at around 119 (the given RGB number for middle grey in a 2.2 gamma).

That simply doesn't work and is assuming a lot.  If you are in a studio setup with a gray card then it is valid, but then that begs the question why you don't just look at the histogram and the highlights and adjust your camera then lock it off for the photo shoot.  Outside of a studio setting without a gray card there are so many things that factor into how the camera comes up with an exposure that delving deeply into one factor while completely ignoring the rest is pointless.

With a digital camera it doesn't matter if the camera under exposes or over exposes.  As long as it does it consistently.  You are always going to have to make adjustments to whatever the camera thinks up because the camera simply doesn't know what it is looking at and it doesn't know what your creative intent is.

Your outside shots are simple.  If you are shooting and the light isn't changing rapidly just take a shot with clouds in it.  Adjust exposure till the highlights in the clouds aren't blown out and then lock everything off.  Only change exposure when light changes.  Don't change exposure just because the subject changes and you will be fine.  Depending on where you are on the planet, the season, and time of day you could shoot for a couple of hours without making any changes to your settings.

Also there is bracketing.  Since the cost of shooting a picture is nil just set your camera up as I indicated and then tell the camera to bracket +/- 2/3 of a stop and you will always have something that is as close to perfect as one can get.

There are so many tools on these cameras now that with a little bit of knowledge and common sense it is easy to get great exposures.

What I would like to see is a camera with multiple manual settings.  For example if you could assign one function key to a present set of manual settings and another to a different preset set of manual settings you could rapidly switch back and forth between them.  This would be helpful if you are going from sun to shade.  Most of the time all I really need is two sets of settings.  Honestly with digital cameras it would be easy to have a bunch of preset manual settings that can be rapidly selected.

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