Dynamic Range – Raw vs. JPEG

I was reading through some comments the other day and saw one that grabbed my attention. In it, the commenter said that they had been told that the dynamic range of JPEG images is the same as it is for RAW images. I had to really scratch my head on this one because I know that there is no way that is true. Of course I just couldn’t let it go so I had to run out and do a little show and tell test to prove it wrong.

Here’s how I conducted my test. First, I set my Canon T4i to capture RAW + JPEG images. This means for every capture I made, I would have two saved copies using the exact same camera settings for each exposure. My subject was a cluster of bright, fluffy clouds floating over my house. Clouds are notorious for getting blown out and leaving behind an unrecoverable blob of whiteness – perfect for my little experiment.

My theory is that if I could pull back as much detail in an overexposed JPEG cloud as I could in a RAW version then I would be wrong and the JPEG would have as much dynamic range as the RAW version.

I set my camera to Manual to get consistent exposures and then started to shoot at about 3 stops over what I determined to be a decent exposure for the clouds. Then I bracketed until I reached a stop or so underexposed, just to give me some good variety in exposures. Then it was on to the comparison.

For the RAW images, I opened Lightroom and did a standard import. Here’s the kind of weird thing about importing RAW+JPEG images in Lightroom. When you do an import, Lightroom will move both the RAW and JPEG images to your import folder but it only shows you the RAW images. If you want to see the JPEGs you need to right-click or CTRL-click (Mac) to open the images in a Finder/Explorer window. Then you will be able to see the JPEGs. For simplicity sake, I just copied all of the JPEG files and put them into their own separate folder called Clouds.

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Next, it was time to start adjusting the images to see just how much dynamic range I really had to play with in each image. For the RAW files, I used the Develop module in Lightroom. The JPEG files were opened in Photoshop using Camera Raw. I figured that this would give me the best apples to apples comparison since Lightroom’s Develop module is using the Camera Raw engine. I started my test by selecting a pretty overexposed image and then started trying to recover highlight details in both images.

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You can see that they both started out pretty much the same although the JPEG is just a bit brighter and more colorful because the camera has already applied some processing to it.

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Once I got the JPEG opened in Camera Raw (above) I started moving the Highlights, Whites, and Exposure sliders in an effort to bring detail back into the clouds. All I ended up doing was making the clouds a bit darker and muddier. There was no recovery of detail but that is pretty much what I expected. Now let’s look at the RAW version of the image in Lightroom.

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As you can see, the whitest parts of the cloud could not be recovered but there is substantial recovery of details in about 60% of the cloud. This is a much better result than the JPEG, which is also as I expected. To be fair though, I went to the next image in the series, which is one stop darker and then performed the same processes.

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The extra stop of exposure really helped the JPEG this time but as you can see, there is still some heavy loss of detail in the brightest parts of the image. Now let’s look at the RAW file.

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As you can see, the RAW file was able to recover all of the highlight data without any blown-out areas. By comparing the two last two images it’s easy to see that the JPEG and the RAW have similar details in the slightly darker parts of the cloud but the RAW file was able to pull out the details in the brightest areas. The JPEG just doesn’t have the range of exposure information available to recover. Here’s a close-up of the clouds from each image to get a better look at both of them; first the JPEG.

 Screen Shot 2013-07-14 at 6.45.04 PM

Not only is there a blown-out highlight there, but there is some pretty significant banding going on where the software was trying to recover the details near the brightest parts of the images. Now here is the RAW close-up.

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As you can see, there is no blown out highlights and no banding. Nothing but glorious image detail. So here is the bottom line, there is nothing wrong with shooting JPEG files as long as you understand that there is not as much image detail in the file so your exposures might need to be more critical. Also, because they do not contain as much dynamic range as the RAW file, you might have to do a little compromising in either your highlights or your shadows. This isn’t to say that the RAW file is perfect and will always contain enough dynamic range that we can always capture the shot with one exposure. If that was the case, there wouldn’t be such a thing as HDR photography.

Now that I have made my case for RAW images having more dynamic range than JPEGs, it’s time to throw a counter-point out there because I know there are those of you just dying to press the Comment button.

Here’s the deal. While the image files themselves have been shown to possess different amounts of image data (dynamic range), once they are processed and displayed, they will have the same amount of visible dynamic range. This is due in large part to the limitations of our viewing devices. Most computer monitors have a limited gamut that can be displayed so truthfully you aren’t seeing everything your image has to offer. Even my awesome Retina display is hampered by 24-bit visibility. So technically when you are looking at a RAW and JPEG image on screen, they both have the same dynamic range, which is limited by the viewing device, not the data in the image file. That being said, go ahead and hit the comment button and let me know what your opinion is on this. Just remember to use your “nice” filter.

Comments

  1. By default, Lightroom hides the JPEGs just like you noted. However, if you want to manage them separately in Lightroom, you need to change a preference. Open Preferences -> General. Check the Treat JPEG files next to raw files as separate photos. This is an application wide setting so will stick even if you switch catalogs.

    And based on my extensive experience in shooting black dogs, I can also attest to the fact that shooting raw gives you much more dynamic range and specifically latitude in post processing.

  2. While it is obviously true that RAW has more dynamic range than JPEG, this little test proves nothing. The ability to recover detail out of seemingly over-exposed highlights has nothing to do with dynamic range. It’s a result of the fact that a sensor is a linear device and our eyes expect gamma corrected data. RAW contains those linear data, so RAW still has 50% of all its data in the brightest stop. That makes it possible to pull detail out of that stop by remapping those data. JPEG is already gamma corrected, so in JPEG the amount of data is equal (and much less) for each stop.

    • I’m pretty sure that he stated the test was to determine if RAW has more dynamic range than JPEG. The test proved exactly what it was designed for. If anything, you could have said there’s no need to test something that, in your words, is obvious. The only practical use of technical mumbo jumbo is to provide terms by which we can discuss photo quality in an effort to improve it. Using it for its own end is kinda silly unless you’re a scientist or engineer. 🙂 <- "nice" filter!

  3. Seems to me the comparative histograms say it all, just a matter of locating the blown highlights in the image.

  4. Another way to compare a captured raw file and a captured JPEG file is by noting the in-camera processing and bit depth for each format. In camera processing is applied to every JPEG (tonal mapping or adjusting, sharpening, color interpretation, and most importantly, a reduction in the total pixel count to accommodate the 8-bit format for JPEGs). Raw files, in contrast, are the actual captured pixels, with no (or very little) in-camera processing applied; raw files preserve all the pixels the high-end camera was capable of capturing and can be saves as 16-bit files. Having a larger total pixel count (and a straight, unadjusted linear capture of highlights, midtones, and shadows) could be the reason that raw files preserve more of the overall color range in a capture.

    With all those unprocessed pixels, edits done in Lightroom or Camera Raw or Photoshop will leave more pixels in each part of the tonal range, so, again, the edited raw image will look better than the JPEG. These digital editing programs actually have to do some interpolation tricks to enable a JPEG to be opened and processed in these apps–so the edited image is composed of original and manufactured pixels, which is less than ideal.

    Peter

  5. Donna Wayne says:

    Thanks for this. I am a really new photographer and have been learning about raw and jpeg. I think I am kind of learning the differences and where either one is better to use. I just went out the other day and shot a few raw images to see what I could do with them. It was pretty fun. But this post was really helpful. I also found this article in my searches that talks about raw and what can be done with it: http://www.paintshoppro.com/en/landing/raw-images/. It has some good info for newbies like me.
    Thanks again.

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