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Photography Lessons With ElCapichan: Your Camera's Dynamic Range

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Today's Lesson: Determining the dynamic range of your camera's sensor and using that to get a better exposure


I am out of town away from my camera for the weekend, and while perusing the latest issue of outdoor photographer, I came across an interesting article on determining the dynamic range capabilities of your camera to help you better determine the proper exposure without spending a lot of time with trial and error or relying to heavily on your camera's metering system. Unfortunately, I haven't tried this method yet myself, so I will be updating in the future with more information and pictures of my own to demonstrate. In fact, I am still trying to work it out in my head how exactly the process works and relates to photographing in the real wold and not just on paper.

Essentially, what the process does is help you figure out the brightest your camera can shoot before losing all detail to the highlights and the darkest your camera can shoot before losing detail in the shadows and then using this information to find the perfect middle ground. Now this method does require you to be able to process RAW images in order to extract all the information possible out of the shadows and highlights. If you have ever shot in RAW and processed the images, you know you bring out a good deal of info without ruining the image. Seeing as I have not yet tried out the process myself (I am really writing this in order to get a better understanding of this myself as well as sharing it with those interested. I promise, photos will be added ASAP) I would like to credit the author of the article, Glenn Randal. The article is in the September 2010 issue of Outdoor Photographer.

Step 1: Determining your camera's dynamic range

Unlike the days of film, where each type of film had a specific dynamic range (from here on out referred to as DR), all digital cameras have their own unique dynamic range. Unfortunately for us, the consumer, there is no published information (by the manufacturer) to let us know what the specific DR of our camera is. Before I go any further, I suppose I should give a better explanation of what I mean by DR here. For those who do not understand DR, it refers to the amount of detail that can be captured in both the shadows and highlights without being under or over exposed. The more detail that can be captured in both the shadows and highlights, the higher the DR. DSLRs are getting better and higher DR with each new generation, but what we see with our naked eye still isn't quite the same as what the camera's sensor picks up. So when I say determine what the DR of the sensor is, I am referring to how many stops between shadow and highlights before there is no saving that lost detail. The method to figuring out the DR of your camera is a simple process but can be hard to wrap your head around exactly how it works and what it all means, and while not an exact science, can be a very useful guide and picking out the correct exposure in those tricky lighting situations.

So to begin, shoot in RAW. This only works when shooting in RAW, as the RAW file is able to store far more information and detail than a jpeg can. With the camera set to shoot in RAW, turn the camera mode to Aperture priority mode, the ISO to 100, metering set to spot metering, and the exposure set at 0. The aperture does not have to be set to anything specific, but you want to have a fast shutter speed to prevent from waiting too long to take the shots. Try f/8-11 and only go lower if there is not enough light. Now we want to find a a subject that is near white and one that s near black. The article explains this by using dirty, white deck furniture and the shadow beneath the furniture. The article doesn't explain much beyond that, but I am going to assume that the light source has to be the same for each in order to truly gage the DR. Now fill the frame with the white subject and press down on the shutter button just enough for the camera to tell you what the proper exposure should be. Remember the shutter speed the meter tells you, cause now you are going to switch to manual and set up everything as it was before and use that shutter speed. You are now going to take a series of the same photo and stop up a 1/3rd stop each time. This means lowering the shutter speed a 1/3rd stop, or in even simpler terms, lowering the shutter speed by a single click of the dial each time. Go no more than 5 stops, or 15 clicks. Now you are going to repeat the process, except this time filling the frame with the shadow. So fill the frame with the shadow, turn the camera back to aperture priority mode, spot metering, 100 ISO, exposure set to 0, and make sure to use the same aperture as before. Press the shutter button halfway to find out what the shutter speed should be and switch the camera to manual. Once again, make sure everything is exactly the same as in the previous steps but plug in that new shutter speed. This time, you are going to stop down a 1/3rd each shot. This means increasing the shutter speed a 1/3rd of the stop, or increasing the shutter speed by a single click of the dial each time. Once again, go no further than 5 stop, or 15 clicks. Now it is on to your RAW converter.

When processing the images, you are going to use a combination of Exposure, Recovery, and Fill Light to to make the images look as good as possible. This means for the images that are overexposed, you are going to want to try a combination of lowering the Exposure and raising the Recovery. The images that are underexposed you are going to want to use a combination of the Exposure and Fill Light . You will notice in some images you can do this and preserve a great deal of detail, but the more over or underexposed you get, you won't be able to get anything from the highlights and the shadows will have a great deal noise. The images right before detail cannot be recovered show your DR. I haven't been able to try this with my camera yet, but I plan to as soon as I can. To give you a better understanding though, I will use the info from the article. When Glen Randal attempted to determine the DR of his Canon 1Ds MkIII, he found out that his camera had a DR of +4 stops to -5 stops. What this means is if you set your camera to take a picture with the exposure meter set to 0, as long as the brightest part of the picture falls within those 4 stops, you will be able to extract the detail from the highlights. If the darkest part of the picture falls within the 5 stops, you will be able to bring out the detail from the shadows. Keep in mind though, that not all lighting situations are the same. Sometimes you may only be able to save the highlights over the shadows and vice versa so You will have to pick. While you may not be able to save both entirely, you can use this knowledge to to perfect one while at least saving a bit of the other.

Step 2: Putting the new knowledge to use


If you have completed step 1 properly, than you should have a good idea on the DR of your camera. Since I have yet to be able to determine the specific DR for my own camera, I will continue to use the example given in the article. To remind you, the camera used was a Canon 1Ds MkIII and had a DR of +4 to -5 stops. So how exactly do you put this to use when you are trying to figure out the proper exposure to use when photographing a nice landscape or cityscape, or even an outdoor portraiture? For starters, lets determine the proper settings you will want to use. Because most camera's metering systems only show a range of -2 to +2, you probably wont be able to start out in manual. You are first going to decide if you are going to want to use a specific shutter speed or aperture. Your decision may depend on if you are using a tripod or not. If you do have a tripod and the scene can handle a longer shutter speed, then you start in aperture priority. If you want or need that faster shutter speed and don't really care about the DOF, then you will start in shutter priority mode. Remember, this is only to gage what the proper exposure needs to be. Once you determine what shutter speed or aperture you will need you will switch to manual to ensure the metering system doesn't take over and change things up on you.

Now lest say you have an nice overcast day. This will provide a nice, even light over everything and prevent contrasty shadows. The only problem on these days is if you want to include the sky, it is usually going to be overblown when exposing for your foreground subject. This is where we can apply what you learned about your camera's DR. Since the 1Ds MkII has a DR of +4 and -5, we know that if we have the exposure set to 0, and the metering system set to spot meter, if we meter for the brightest part of the sky, we can safely open up 3 stops and still be able to recover the detail from the sky. This should then put your foreground subject at one stop under midtone. Now remember, you have to judge how to use the info in each situation. Because overcast skies can be very bright compared to the ground, you do not want to open up too much.

With practice, you will eventually have the perfect idea for each shot whether you want to meter for the highlight or shadow and which one to put below or above midtone. As long as you keep your subject within the boundaries of your camera's DR, you should always be able to have adequate detail in you subject. The key is to be able to get at the very least your subject and either the highlights or shadows within the DR, but if you can manage to get all 3 within your camera's DR then even better.

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Updated 12 Sep 2010 at 12:39 AM by ElCapichan

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Comments

  1. ElCapichan's Avatar
    Let me know what you think of this one. Is it hard to follow or understand? Any parts that need a bit more clarifying or just don't make sense? After spending hours on the subject the last 2 nights, I feel I have a decent grasp on how it works and how to apply it to different situations. I hope to put it to the test this week and get some pics of my own up and my thoughts from my own personal experience.
  2. Razor Ramon's Avatar
    I think this one is gay.
  3. ElCapichan's Avatar
    Did you ever think these blogs weren't necessarily meant for you?

    More pretty pics to come with the next blog.
  4. Razor Ramon's Avatar
    Every blog can use a bit of me.
  5. ElCapichan's Avatar
    No... they don't.
  6. Doc Holliday's Avatar
    This was a technical column, why the fuck does it need pictures?

    Also, I need to do this with my Rebel. I've also been meaning to test the noise in the ISO setting - leaving the dust cap on, taking shots at the different ISOs, then bumping up the contrast to see which are the cleanest.
  7. ElCapichan's Avatar
    I took the test shots with my 5D MkII today. I haven't gone through with them in RAW yet to determine the DR range. I am still not sure how useful this would be for determining the proper exposure. I'll experiment with it more tomorrow, but seeing that not all lighting is the same, it is more of a theoretical guess than an exact science. The article also mentioned that color has its own DR that if shot out of that range, colors could become washed out or dull when trying to fix them in RAW and PS. I will add that in when I finish my own tests.

    The noise test is interesting when you see the images back to back, Just keep in mind though that if you have lots of good light, the images will look much better than images shot with the same ISO in poor light.
  8. Dunlap's Avatar
    I think it's a bit hard to follow, because you need to have learned a bit about exposing before you understand the range of your camera.

    Basically, from what I've learned in a book about film and exposure control, is to imagine the range from black to white segmented into 11 shades, with 0 as black, 5 as middle gray, and 10 as white. When you meter, you get a reading for what will get a middle gray exposure. So if you are spot metering, the exposure you get will make what you've metered into the middle tone. If it's a shadow area, you're going to get a lot of detail in the shadow, but everything lighter is going to get really bright, and if you're metering a light area, everything else is going to get dark. Now the trick is, it takes a full stop to move your exposure one step on your gray scale, so what you can do is, like in ElCapichan's example, is meter the sky, and then change your exposure 3 stops to put it at an 8, so now you have your sky bright, but you can still get details because it's not set to total white.

    What I've described is with film however, and I think this blog is about the difference between film and digital determining how many stops there are between black and white? I've always just assumed it was 11 stops and have worked like that, but I don't do a lot of photography so it hasn't been a huge issue for me.
  9. ElCapichan's Avatar
    I agree, this one can be tough to follow. Like I said, it took a few reads and time to understand. I'll have time tomorrow to add my own experience and thoughts to it as well as some pictures.

    The DR between digital and film is very different, though it bears mentioning that different types of film have different DR as well. The thing about digital is that no camera is the same and same with lighting. There are going to be situations where the light is just to bright to capture detail in everything. Oh, and this also only works in RAW. If you shoot jpeg, you can't recover all the data your sensor is capable. I actually want to test this in a better light condition tomorrow to try and get a better idea.

    I will try to work on this tomorrow and make it flow better. Thanks for the feedback,
  10. ElCapichan's Avatar
    Test Shots

    Here are a couple of test shots I took with my 5D MkII. With my 5D MkII, I determined I could shoot either 3 stops over or under and still have a usable image. With just some basic RAW work using Exposure, Recovery, Fill Light, and Brightness, I was able to get the images looking similar to those shot for the midtone exposure. The color was a little off, but with some more work, it would be possible to get the color to match even more. Even without getting the color to match perfectly, they still looked good. I found I could go another 3rd of stop over and under, but the image started to deteriorate. It could be usable if you absolutely had no other way to get the photo.

    EDIT: Photos down. Will be back up shortly.
    Updated 20 Sep 2010 at 09:51 PM by ElCapichan
  11. MechDeus's Avatar
    Images aren't working.

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