Exposure Accuracy - How important is it?

This is probably a stupid question, but I want to find out if I'm missing something.

I'm not completely new to photography. I understand the basics of the zone system and the importance of getting an accurate exposure. But I have to admit, I find a 1/2 stop difference barely perceivable. If I take two shots with 1/2 stop difference, I can almost never decide which is better (assuming they're both close). The only time I can tell is when I'm way off, in which case, neither shot is good and I should have bracketed at whole stops.

Considering the adjustments we can make digitally, or in the darkroom, this amount of accuracy in the exposure seems like overkill. Can anyone explain to me what kind of circumstances require 1/3 (or even 1/2) stop accuracy? And in those circumstances, what difference does it make in the final print?

I'm just trying to figure out if there is a benefit of being this accurate that I'm not aware of.

Thanks!

Paul

Paul, that's a good question. And you're right, exposure accuracy to that degree doesn't usually matter, especially now that we have photoshop, and noise reduction software if needed.

Exposure accuracy is more important with digital and slides, less so with negative film.

I think it also depends on your subject. With sunsets I bracket in full stops. With people, half. The only place I've heard 1/3 stops being important is in accurately reproducing artwork, in which the colors and density need to be just right.

Be interested in hearing what others have to say.

Rick

I don't know if there really is an "accurate" with exposure. What I mean by that is that the meter reads one thing and the exposure that you want might be something else. You might choose to over or under expose just to give you some options for post processing too. For example, slightly overexposing a RAW file at a higher ISO, so that when you bring it down in Photoshop some of the noise won't be as visible. Usually high ISO and overexposure doesn't go together in my case because I'm shooting in low light and doing what I can just to get a decent shutter speed and don't really have anything to spare, but it's a theory.

I try to be as accurate as I can at the time of capture, in the sense that I get my histogram close to what I have in mind. Lightening a dark shot can increase noise. I know that Noise Ninja works wonders but it's one more step and can change the look of the shot (not very experienced with it myself though). Also, if you underexpose to keep the highlights from blowing out, then lighten in PS the light areas might not look right. I don't think that a couple of blown highlights is always a bad thing.

Depends on the shot and your intention with the final look of the image and/or print. Someone told me that Ansel Adam's negatives would look horrible with straight printing because he shot his negatives to give him options he wanted with his amazing darkroom skills. I don't always shoot this way - sometimes it's just not necessary - but sometimes it helps make the final image better.

Rick and Steve, thanks for your replies. You guys are explaining things pretty much the way I thought, but it's nice to know I'm on the right track. I guess I'll just have to learn when it's important to be accurate and when it's not, through trial and error.

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Originally Posted by another view

I don't know if there really is an "accurate" with exposure. What I mean by that is that the meter reads one thing and the exposure that you want might be something else. You might choose to over or under expose just to give you some options for post processing too.

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I think I'm using the wrong word. I think precise is the right word, not accurate...I always get them mixed up. I'm talking about having the ability to make adjustments on a smaller scale than I can distinguish.

For example: I can take 3 shots at 1/2 stop increments, with the middle being "perfect." Then I can take the other two and tweak them in photoshop by a 1/2 stop and get them so close to the one that was exposed "perfectly" that the three are indistinguishable. Am I missing something? Does the photoshop editing have a detrimental effect that I'm just not noticing?

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Originally Posted by another view

For example, slightly overexposing a RAW file at a higher ISO, so that when you bring it down in Photoshop some of the noise won't be as visible.

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I know that overexposing is generally bad with digital. Does RAW handle over exposure better than jpeg?

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Originally Posted by another view

I try to be as accurate as I can at the time of capture, in the sense that I get my histogram close to what I have in mind.

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I need to learn how to use that histogram thingamajig. :)

Paul

Exposure accuracy is just as important in RAW as it is in jpeg. Exposure accuracy means detail and colour in both the brightest and darkest areas of the photo. Under or over-exposure means that you are losing colour information from the pixels in those dark or bright areas. If you try and bring that colour back through Photoshop, you are adding noise, reducing colour gradations and reducing detail. If you have a good eye, these weaknesses are easy to see.

In extremely contrasty situations, it is probably best to do two shots from a tripod: one metering for bright areas and the other metering for dark areas. Then use a tonal map and blend the two photos in a HDR photo editor...which is better than the HDR approach in Photoshop CS2.

Ronnoco

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Originally Posted by Ronnoco

Exposure accuracy is just as important in RAW as it is in jpeg. Exposure accuracy means detail and colour in both the brightest and darkest areas of the photo. Under or over-exposure means that you are losing colour information from the pixels in those dark or bright areas. If you try and bring that colour back through Photoshop, you are adding noise, reducing colour gradations and reducing detail. If you have a good eye, these weaknesses are easy to see.

In extremely contrasty situations, it is probably best to do two shots from a tripod: one metering for bright areas and the other metering for dark areas. Then use a tonal map and blend the two photos in a HDR photo editor...which is better than the HDR approach in Photoshop CS2.

Ronnoco

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Hi Ronnoco, thanks for commenting. I understand what happens when you under and over expose. I'm just trying to understand at what level it makes a practicle difference. When you say the weaknesses introduced in photoshop are easy to see, do you mean in a print, on the monitor, or both? And are you saying it's easy to see even with a change of only 1/3 stop?

Blending two photos for a high contrast scene is something I want to learn how to do. I'm sure it's great for certain types of photos. Do you happen to know if it can be done in PS 6.0? Yep, I'm out of date. What does HDR stand for?

Paul

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Originally Posted by photophorous

Hi Ronnoco, thanks for commenting. I understand what happens when you under and over expose. I'm just trying to understand at what level it makes a practicle difference. When you say the weaknesses introduced in photoshop are easy to see, do you mean in a print, on the monitor, or both? And are you saying it's easy to see even with a change of only 1/3 stop?

Blending two photos for a high contrast scene is something I want to learn how to do. I'm sure it's great for certain types of photos. Do you happen to know if it can be done in PS 6.0? Yep, I'm out of date. What does HDR stand for?

Paul

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Well, the level that it makes a difference depends on the camera. In the superzooms and some DSLRs with live preview you can actually see through the viewfinder the effect of exposure changes as you make them and 1/3 stop differences. On a sunny day, I have needed to underexpose up to 1 stop to avoid blowing out highlights. Overexposing even 1/3 stop would have added to lost detail.

To see what I mean, shoot a person in the shade wearing dark pants and a pale coloured shirt/blouse of all one colour. Properly expose the first shot and shoot the second shot at 2 stops under-exposed. Bring back the second shot to the same as the first, using Photoshop, then close up look at noise and compare the colour, skin tones, and gradations between the two shots. If you see the difference in these, you will start to notice it in less drastic differences in exposure.

As to being out of date, you are definitely not the only one, considering the cost of Photoshop CS2, at approx. $800 CDN. HDR is high dynamic range and the software creates what seems to be an impossibly detailed and well lit photo with a considerable range of colour tones.

Ronnoco

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Originally Posted by photophorous

Does the photoshop editing have a detrimental effect that I'm just not noticing?

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Yes. Whenever you lighten an image, either in PS or printing, you increase noise and/or grain. This is largely what Ronocco is referring to below. You can avoid this by exposing properly. I used to overexpose my negatives by a stop or so so that when I printed them, I could print darker and remove grain.

Bracketing is a pretty good idea. But, when time or resources don't allow, that's when our expensive camera's 256,000,000 segment multifunction algorythmic computer computation exposure meters come in handy :D

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Originally Posted by walterick

But, when time or resources don't allow, that's when our expensive camera's 256,000,000 segment multifunction algorythmic computer computation exposure meters come in handy :D

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Must be a Nikon thing..my Minolta only has 19...I bet thats why they got out of the biz:D

Actually... the cameras I use most, my FM2N and my Mamiya, both have centered-weighted meters. No problems with exposure yet. The Mamiya also has a spot meter.

I wonder if the new generation of photographers even know what center-weighted is?

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Originally Posted by walterick

I wonder if the new generation of photographers even know what center-weighted is?

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:idea:

Center weighted is what happens as you get older and try to lose weight and everything else gets skinnier except your mid section....:rolleyes: :D

Hope that helps explain it---but how does that pertain to photography?:confused:

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Originally Posted by photophorous

I think I'm using the wrong word. I think precise is the right word, not accurate...I always get them mixed up.

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I said that because a lot of people seem to be under the impression that there is only one proper exposure reading for a shot. This really isn't true, especially if you have some post-processing techniques in mind and/or the scene has more contrast than the sensor can record, etc. I preach about using spot meters alot, and this is a situation where you could use it to get (for example) the rock in the foreground of your shot at +1, regardless of what the background is. That would be hard to do with a center-weighted, matrix or evaluative metering pattern but the histogram is the "final answer" for me.

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Originally Posted by photophorous

For example: I can take 3 shots at 1/2 stop increments, with the middle being "perfect." Then I can take the other two and tweak them in photoshop by a 1/2 stop and get them so close to the one that was exposed "perfectly" that the three are indistinguishable. Am I missing something? Does the photoshop editing have a detrimental effect that I'm just not noticing?

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Digital Photo Pro magazine has a "myths" column inside the back cover of each issue. A couple of months ago, it was about underexposing to hold the highlights and then lightening in Photoshop. They showed an example of doing this vs. exposing at the meter reading (with studio strobes in their example) and the light areas of the shot looked completely different.

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Originally Posted by photophorous

I know that overexposing is generally bad with digital. Does RAW handle over exposure better than jpeg? I need to learn how to use that histogram thingamajig.

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RAW will give you a better chance than jpeg here, a lot of it having to do with 12-bit vs. 8-bit. That extra color depth will make any exposure changes come out smoother. But don't fall into the trap of "fix it in Photoshop". You'll wind up with a better image and have to spend less time with it if the capture is as close to what you want as you can get it. The histogram is IMO the most valuable tool of a digital camera. The LCD isn't a good judge of exposure but the histogram doesn't lie!

Damnit Steve now you're gonna make me go learn how to use a histogram aren't you?!

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Originally Posted by natatbeach

---but how does that pertain to photography?:confused:

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Because you're beautiful to photograph no matter how center-weighted you are :wink:

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Originally Posted by walterick

Damnit Steve now you're gonna make me go learn how to use a histogram aren't you?!

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Yup. Good topic for a new thread, let me come up with some examples! :thumbsup:

Don't you just make sure everything is in the middle?

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Originally Posted by walterick

Don't you just make sure everything is in the middle?

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No. Think about it this way - the middle of the histogram is "middle grey". If you're shooting snow, you'll have grey snow. If you're shooting a black lab, it'll be a grey lab. Work on "previsualizing" what the histogram should look like, then just confirm that you got what you want once the image is recorded.

Ding dang it! I was saving that for the thread... Snow and black lab examples, even...

Haha.

You can still use the lab examples in the other thread I won't tell anyone :wink:

So, basically, a histogram is like a built-in, 21st century grey card.

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Originally Posted by walterick

Because you're beautiful to photograph no matter how center-weighted you are :wink:

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Smooooth! Do you give lessons in how to talk to women? I could really use 'em. :blush2:

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Originally Posted by another view

Yup. Good topic for a new thread, let me come up with some examples! :thumbsup:

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That's a great idea. I don't understand that thing, but it looks important. :D

Thanks!

Paul

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Originally Posted by walterick

So, basically, a histogram is like a built-in, 21st century grey card.

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Yeah, just like a fish is to a bicycle. No, wait... :)

I guess you could think of it that way but the histogram comes up after you've taken the shot unlike metering with the grey card before you shoot. You use the grey card because your experience tells you that this is a time that you need to use it, and know what you'll get (for the most part) by doing it that way. You won't know 100% (other than your own experience with that particular film) about shadows and highlights though. The histogram tells you all of this.

Guess I better get looking for some examples. I think I'll do screenshots in PS showing the image and it's histogram, now that I finally figured out how to do that.

I haven't read the other posts, but to me proper exposure is critical, even if you are shooting digital. Once you start to add exposure through photoshop you start adding noise which isn't good. Also, having proper exposure will also save you a ton of time in post processing.

I learned exposure using slides where you cannot make a mistake. I now still shoot as if I am shooting slides.

Relying on photoshop is bad, when good technique will allow you to shoot more than edit.

Loren

same here. proper exposure really helps to maintain the right color balances and "trueness" of the scene. When you underexpose and boost, you both gain noise and you lose a lot of the color. You can bring it back a bit, but if you properly exposure in the first place the colors will be that much better.

Nope. You either have it or you don't :D

Kidding. Listening to women is the greatest women tutorial you'll ever get. You have to learn how to hear what they're saying, ignore how they're saying it, see through to their actual underlying message, store it somewhere in the back of your mind, and bring it up somewhere in the future in such a way that lets them know that you were listening and you understood them. All without seeming like you're a player.

That's all :D

Plus, it doesn't hurt to have an open heart, as unmanly as that seems :)

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Originally Posted by livin4lax09

same here. proper exposure really helps to maintain the right color balances and "trueness" of the scene. When you underexpose and boost, you both gain noise and you lose a lot of the color. You can bring it back a bit, but if you properly exposure in the first place the colors will be that much better.

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I strongly agree with Brent and Loren. Get the exposure and balance right in the first place and don't depend on software to correct bad technique.

Ronnoco