Over expose in RAW?

[ellery]

<p>Hello everyone,</p>

<p>I was reading a photography magazine while traveling recently and one of the articles suggested over exposing RAW images to the point close to but not clipping - then take them back to the desired exposure for better results - the author of this article use an actual example and the one slightly overexposed then adjusted did appear improved? I had taken a beginner course and the instructor had told us, that if one had to either over or underexpose, then under exposure is better to recover.....I generally try to just get the exposure that I want in the camera to limit my time in post processing, but is it good advice or under certain conditions to systematically/routinely over/underexpose in RAW then adjust? Or should I keep at what I am already doing?</p>

[blockphoto]

<p>Generally with digital cameras there is cleaner detail in the highlights than the shadows, thus the standard phrase "expose to the right", which means the histogram should show the curve of all channels moved to the right (brighter) side of the graph without actually clipping, then you can bring the exposure down in software to get all of the needed detail and shadow. By contrast (heh), if you "expose to the left" (underexpose) and try to bring detail out of the darker tones by raising the exposure in software, often you will end up with noise in the shadow areas because of the way digital sensors operate. It's been a while for me, but I remember film being the opposite, or at least allowing equal leeway in both directions.<br>

<br />I'm hoping in the future digital sensors will handle shadows better, and this won't be a necessary consideration anymore...certainly less true than it used to be with new sensors and noise reduction software, and I don't worry about it that often.</p>

[john_a5]

<p>The problem I see with this is that who is that good at knowing the limit? I think the adage was true when the cameras first came out, but there have been great improvements with noise in the shadows, both in what the camera does and what the raw processor can do. I think exposing properly is the best bet!</p>

[ben_goren]

<p>Ellery,</p>

 

<p>In theory, it’s a good practice. In practice…it’s a lousy theory.</p>

 

<p>First, it’s <em>very</em> easy to blow the highlights by doing this, so it only makes

sense for low-contrast scenes.</p>

 

<p>Second, the basic effect is to lower the ISO (and thereby to reduce noise). But modern SLRs

are so noise-free at base ISO that there’s nothing more to be gained. Sure, you could gain

some quality with ETTR at higher ISO, but not as much as you would by simply shooting at a lower

ISO in the first place. Besides, if you’re worrying about noise at even ISO 400 on a modern DSLR, you’re nuts.</p>

 

<p>So use the histogram to make sure you’re not clipping important highlights or blocking

important shadows. If your shadows and highlights are safe, aim for a “standard”

exposure, and consider your exposure work done. When in doubt, brighter exposures are better — but only if the highlights are safe.</p>

 

<p>Cheers,</p>

 

<p>b&</p>

[ellery]

<p>Great points everyone - thanks for the education - I can imagine a higher contrast scene would be tricky to "expose to the right" (that was the terminology used in the magizine I recall now that you all spelled it out) - may easily lose detail if you are not careful - that makes total since. I thought that teacher was full of crap on that point as I had already read about this concept in in another book before taking the beginner course (John Hedgcoe book if I recall). Anyway, just an academic question really that I will keep in the back of my head.....thanks everyone for clearing that up!</p>

[dan_south]

<blockquote>

<p>I had taken a beginner course and the instructor had told us, that if one had to either over or underexpose, then under exposure is better to recover.</p>

</blockquote>

<p>Within limits, this principle is true only for COLOR POSITIVE film (a.k.a. slide film). Digital sensors work more like print film, i.e. slight overexposure is better than slight underexposure. However, print film is a lot more forgiving in its handling of highlights as opposed to a digital sensor. Watch your blinking highlights display and lower the exposure level if you have to. Overloaded "blinking" highlights cannot be recovered</p>

 

<blockquote>

<p>I generally try to just get the exposure that I want in the camera to limit my time in post processing.</p>

</blockquote>

<p>You'll be fine if you continue to work this way. You might sacrifice a little bit of detail or capture some shadow noise in the occasional high-contrast shot, but most of the time you're not going to gain anything from strict adherence to ETTR.</p>

<p>It's actually very difficult to follow the ETTR principle precisely. The histogram in most DSLRs reflects the content of the JPEG preview file, not the RAW file. If you try to compensate by pushing the highlights a bit beyond the blinking stage you run the risk of blowing those highlights. The results will look horrible and won't be easy to fix (if it's possible at all). </p>

[sknowles]

<p>Consider you can test this with a scene with the range from dark shadows to bright highlights by bracketing from -1 to even to +1 stops, or even +/- 1.5 to 2 stops, and compare the raw files with the exposure and adjustments in the photo editor. It will teach you how your camera performs. Good luck.</p>

[chrisnielsen]

<p>Just be careful - the blinking highlight warning may not be 100% accurate either, something tells me it's not operating on all three channels. So you might easily blow highlights on just one channel without realising it</p>

[paddler4]

<p>Re Chris's comment: yup, you can blow one channel when the overall histogram looks fine and there are no blinkies. I have had this happen a number of times, usually with the red channel. Red flowers, in particular, are a problem. I took gobs of terrible shots of cardinal flowers before I realized what was going on. The best thing if you have really uneven luminance across channels is to have the lcd set to show separate histograms as well as the overall histogram. On the newer Canons that have large LCDs, there is room for this, although just barely.</p>

<p>That said, I still try to expose to the right while being careful not to clip.</p>

<p>BTW, there have been a bunch of postings about ways to get the histogram to be more accurate if you are shooting raw. I don't recall the postings or the details, but I just checked mine, and started with the neutral picture style and turned contrast and sharpness to 0.</p>

[scot]

<p>I like Dan South's advice to 'Watch your blinking highlights display and lower the exposure level if you have to. Overloaded "blinking" highlights cannot be recovered.'<br>

That's what I do, and for me at least, it works better than checking the histogram.<br>

--Happy Holidays,<br>

Scot</p>

[ellery]

<p>Well, I will have to dabble into this and see how this all plays out I suppose - I hadnt really thought about the histogram reading the JPEG and not the RAW file - that is very interesting....I will have to look up what Dan K was talking about I suppose - Thanks again everyone for all the great insights! I will keep them in mind and see how I do!</p>

[mr._c]

<p>if your pic is a landscape or still life, then over exposing can work.<br>

as you get more detail and info from the shadows. (resulting in a bigger raw file)<br>

you should watch out for whites (reds?) clipping channel. or you can bracket 1ev, or 1/3, or 1/2 ev.<br>

if there is wind or movement, overexposing will give you a slower shutter speed. so match your iso, aperture, and shutter to the scene. use tripod if you prefer.</p>

<p> </p>