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Over the years that I’ve worked as a photography writer I’ve noticed that people keep asking the same questions about exposure on their EOS cameras.
One of the most common is why doesn’t the camera get the exposure right every time?
This is a reasonable question. Modern digital SLRs are advanced machines with built-in microprocessors that can handle complex calculations. So just why do they get exposure wrong?
Part of the reason is that the light meter inside a camera measures reflected light. If a scene is darker or lighter than average, the camera may return an incorrect reading.
But think about this for a moment. Who gets to say whether a given exposure is correct or not? I don’t like using the word correct in relation to exposure because it implies that there is only one right answer.
I prefer the term ‘optimum exposure’. This is the exposure setting that is best suited to the scene that you are photographing and the medium you are using.
Imagine that you are photographing the same subject with four different cameras. One is loaded with black and white film, another with colour transparency film, the third with colour negative film and the last is a digital camera. Each has the same lens and frames the subject the same way. The quantity of light falling on the subject is also the same.
Potentially, the scene could require four different exposure settings. That’s because each camera is using a different medium which reacts to light in a slightly different way. Film users will know that black and white film, slide film and colour negative film all need to be treated differently. The same goes for digital cameras.
Put simply, the optimum exposure depends as much on the medium you are using as the quantity of light falling on the subject.
That’s another reason why cameras get exposure wrong. The metering system has yet to be invented that takes into account the medium being used as well as the amount of light entering the lens.
Even with digital cameras, the optimum exposure may be different depending on whether you are using the JPEG or Raw format. In JPEG, the aim is to get the exposure as precise as possible. That’s because there isn’t much leeway in post-processing to make the image darker or lighter, and you certainly can’t bring back shadow or highlight detail lost due to poor exposure.
In Raw the aim is different. The idea is to create a file containing as much information as possible in preparation for converting to the JPEG or TIFF formats in Raw processing software. That may require different exposure settings.
Exposing to the right (often referred to as ETTR online) is a technique used by photographers to create a Raw file containing the maximum amount of possible information.
The technique is simple – you use the exposure settings that allow the maximum amount of light possible to reach the sensor without clipping the highlights. The result is a histogram with a graph that is as close to the right hand side of the graph as possible without crossing it.
The main benefit of exposing to the right is that it reduces noise levels in your photos. It also ensures that you capture as much shadow detail as possible, without losing any highlight detail.
Lets take a look at how this works in practice:
Here’s a photo take at my camera’s recommended exposure settings. It doesn’t cover the full range of the graph. The right hand fifth is empty. This tell us we can increase exposure without clipping any highlights.
Here, I increased the exposure by a stop using exposure compensation. The histogram is further to the right, but no highlights have been clipped. These are the optimum exposure settings.
This is what happens if you increase exposure by too much. Here, I increased exposure by two stops. The histogram is cut off on the right hand side and the highlight alert (black region of photo) shows the clipped areas.
So, what’s the best way to put the exposing to the right technique into action?
A lot depends on what you are photographing. If your subject is static (such as a still life or a landscape) you have time to take a photo, look at the histogram, then change the exposure settings and take another one if necessary.
If you are shooting something like portraits or street photography you probably don’t have the luxury of time. But you should still check your histogram every now and then to see how your exposure is doing. If you notice that your camera is consistently under- or over-exposing the image, you can make an adjustment using exposure compensation. You may even find it easier to switch to manual mode. It’s your call – the most appropriate response depends on the situation.
The effectiveness of exposing to the right really depends on the contrast range of the scene that you’re photographing.
If you’re shooting a high contrast scene then you may find that you can’t successfully capture all the tones that you would like to, let alone use a technique like exposing to the right. The most common scenario where this might occur is in landscape photography, as the sky may be much brighter than the land.
If this happens to you, ask yourself whether the high contrast is a signal that you are shooting in the wrong light. It may be that you need to come back when the sun is lower in the sky. The quality of the light will be better and the contrast will be lower.
If the light is good, then there are two good options for dealing with the excessive contrast.
One is to use a graduated neutral density filter to reduce the brightness of the sky.
The other is to set the camera on a tripod and take two separate exposures, one for the sky and the other for the land, then merge the correctly exposed parts in Photoshop afterwards.
Here’s a landscape with a bright sky.
I created this version by taking separate images for the sky and the land and blending the two in Photoshop.
If the light is flat then your camera will have no trouble capturing all the tones of your subject. The histogram occupies just part of the graph, and you can push it to the right by increasing exposure.
In this photo you can see that the histogram occupies just part of the graph. It is possible to increase exposure and push the histogram to the right to create a better quality Raw file.
Finally, it helps to understand where the histogram comes from. When you take a photo on your EOS camera, even if you have selected the Raw format, the camera embeds a JPEG version of the photo you have just taken in the Raw file. The JPEG file is processed by the camera using the Picture Style and White Balance settings you have selected. The camera displays the JPEG file on your camera’s LCD screen when you play back your images.
The important thing to understand is that the histogram is generated from the JPEG file, not the original Raw file. This is significant for two reasons.
The first is that Raw files contain more highlight detail than JPEG files. If the histogram indicates that there are clipped highlights, that just means that the clipped highlights exist in the JPEG file. The highlight detail might be intact in the Raw file.
Some photographers may use this fact to encourage you to increase exposure to the point where the histogram shows clipped highlights, on the basis that you can pull back the lost detail when you process the Raw file. You can try that if you wish, but you’re taking bit of a risk, as you never really know at what point your highlights will clip.
The other thing to be aware of is that if you go into your Picture Style settings and increase the contrast, that only affects the JPEG thumbnail and not the Raw file. The more you increase contrast, the less accurate the histogram becomes in relation to the Raw file.
My ebook Understanding Exposure: Perfect Exposure on Your EOS Camera covers everything you need to know in relation to exposure on your EOS camera.
June 28, 2013 09:50 am
Awesome, I'll be trying this when I take some landscapes next week in Kings Canyon. Thanks for the tips :D
June 17, 2013 12:36 pm
Glen Millr - EOS is Canon's name for their SLR system produced since 1987 that is centered around the EF (Electro-Focus) lens mount. From Wikipedia:
"The Canon EOS (Electro-Optical System) autofocus 35 mm film and digital SLR camera system was introduced in 1987 with the Canon EOS 650 and is still in production as Canon's current DSLR and recently released Canon EOS M mirrorless interchangeable-lens camera (MILC) systems. The acronym "EOS" was chosen for Eos, the Titan Goddess of dawn in Greek mythology, and is often pronounced as a word (UK /?i?.?s/ or US /?i?.??s/), although some spell out the letters, reading it as an initialism."
June 17, 2013 12:13 pm
Glen, EOS isn't exactly an acronym (it is, but from 1987 and is now used as a name). It's what Canon calls their SLR cameras. Not elitist, just assuming that someone who's on the digital photography school website might not need to have the name of one of the two most common cameras out there explained to them.
June 16, 2013 09:54 am
Enjoyed your article as I have tried to shoot in this manor- Sometimes tho not having the time to always double check the histogram. My question is: I noticed you are shooting in sRGB. When most all processing is done in "RGB" only. I realize the printer can only print in sRGB but....Most articles Ihave red say to use "RGB" in the settings of the camera. May I ask why You choose to shoot in sRGB??
Thanks!! Appreciate you writing the article!
June 14, 2013 08:34 am
'pah', you're ignoring Shot (photon) noise. If a particular detector pixel collects n photoelectrons in a given exposure period, Shot noise is sqrt (n). Thus, if you double the exposue time, noise is reduced by sqrt (2). Quadruple it, and you halve the Shot noise.
June 14, 2013 08:09 am
I usually underexpose by 1/3 stop and set the contrast and color high on my 30D to ensure that it looks good when I am planning on looking at the pictures in a digital medium (facebook, etc...). I shoot JPEG instead of RAW, since I do not want to re-edit the images once I have taken them. I strive to get the image right in the camera.
One thing that puts me off: the pictures that are truly shot ETTR,almost always look blown out when you pull them up digitally. They look fine when Walmart gets ahold of them to print. Occasionally, the -1/3EV pictures are so dark you can hardly tell what is going on in them when you get them back.
I shot a few events where the ISO had to be really high to even get my (-1/3EV) image to show up. I am almost always having to go back in and mess with the images to raise the light and get back some of the details that get left in the dark. I will have to try the ETTR in those cases and see what comes of it, since it's not like I won't be going back into the pictures later anyway.
Thanks for the advice!
June 14, 2013 06:53 am
Andrew. Best explanation I have ever heard. If the rest of your book is as good, it is now a must have item for me. Are you saying leave the camera in default mode for all settings? Would that include noise reduction?
June 14, 2013 01:19 am
Are we trying to be elitist by not explaining our acronyms? Not a good idea to title an article using only the term "EOS," especially when the full term is never given in the article.
Just a thought.
June 14, 2013 12:53 am
You advocate chimping to ETTR...why not shoot in manual mode when ETTR by simply neutralizing the "picture style" settings>exposing the histogram in LV>inputting two of the three camera settings and using the third setting to push that histogram close to the right edge.
June 14, 2013 12:32 am
Brilliant stuff! I wish more people understood and used ETTR, you mention it to most people even seasoned shooters and they look at you with that "You're one of those digital gimmick shooters." looks and think you're odd!
I use it all the time while I'm shooting landscapes, it takes some getting used to seeing your images almost blown out 'cos they're look so overexposed you have to have a leap of faith that the sensor sees all and you put your trust in the almighty histogram! In order for it to work you have to really get into the mindset that the screen image is purely 100% for composition only and trust the histogram as your friend.
June 13, 2013 05:22 pm
Great article and well explained, regardless of the camera used this knowledge can be put to good use. I know from my time working as a photographer that slightly over exposing( without blowing out highlights) gives less visible noise. Regardless of how this works or its explanation it is true.
June 12, 2013 09:18 am
I expose to the right only when shooting RAW and taking the time to shoot carefully.
When I shoot jpeg, I like to use live mode to capture exactly what i see and when i feel lazy.
But at the end of the day, I'ts usually what pleases the eye that i tend to go with. I don't like to wast too much time post processing. the key is practice, practice, practice and you'll find your own style and what makes a good picture to you own eye.
The rules are great to follow if your a pro. If your a hobbyist like me just relax and take your best shot. don't sweat the small stuff.
June 11, 2013 06:33 am
I definitely do this. Get as much detail as you can possibly capture, then you can adjust in post according to what your style suggests. I want to have as much detail as possible so that I can choose what to keep and what to eliminate (if any).
June 10, 2013 08:19 pm
Jay: I set the Picture Style to whichever is most appropriate for the photo then leave it at the default setting, for that reason.
David: You can expose to the right with any digital camera that supports Raw files.
Pah: Er, that's what I meant. I just condensed it to a single sentence. The net result of exposing to the right is less noise.
June 9, 2013 07:25 pm
I find the article very informative with good examples. Very useful even though I shoot Nikon :-)
June 9, 2013 06:43 pm
"The main benefit of exposing to the right is that it reduces noise levels in your photo"
This is actually an incorrect expression as the noise is an intrinsic feature of the sensor. Exposing to the right improves the signal-to-noise ratio i.e. the more you give the light to the sensor the larger your signal will be. One cannot influence to the noise by adjusting the exposure. Only ISO setting amplifies the noise (as well as equally the signal)
June 9, 2013 04:11 am
Can we use the same technique without EOS or is it somehow different?
June 9, 2013 03:22 am
Excellent write up.
Is it then better to leave the (JPEG) settings in default or standard mode when shooting on RAW mode, so that the histogram is "neutral" as possible?
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