You shouldn’t under-expose your photos

Why under-exposing your photographs does not lead to better pictures.

Hi, my name is Rich Dyson, and this is Coffee Break Photography from Edinburgh Photography Workshop.

This week’s video is going to be slightly different. I run a beginner’s photography workshop here in Edinburgh. The sessions teach the basics of exposure, composition and editing. At the very end of the workshop, I always leave an offer for the participants. If they want additional advice after practising, they can drop me an e-mail, and I’ll endeavour to help them. That’s what happened a couple of weeks ago. 

I received an e-mail from a client we’ll call Frances because that’s her name. Frances asked me to review some images to see how she was progressing. She also told me she’d been given a tip to “take photos under-exposed so there was plenty of data to work with in the edit”.

When I am carrying out an image review, I ask for an edited JPEG file so I can see what the end intention of the photographer is. I also ask for the original RAW file to understand how the picture was taken originally. 

Now, I want to put one thing to bed right at the start of this video. Any comments I make are my opinion of the photographs. I try to justify my opinion rather than saying something is good or bad. If you disagree with my opinion, that’s absolutely fine, but don’t just tell me I am wrong; tell me WHY you think I am wrong.  

To start the review, let’s look at the JPEG images. Overall, the three images show a good understanding of the technical elements of taking photos. All three images are sharp, there is a clearly defined subject where the focus is drawn, and they are all interesting shots. So, at a high level, these are pictures taken by a competent photographer. 

However, a few things can help improve these photos, so let’s look at each individually. The first thing I want to talk about is exposure. In Frances’s email, she mentioned that someone had told her it was better to under-expose images. I’m not sure who gave her this advice, but in my mind, it is bad advice. Rather than just taking my word for it, I’ll prove this through a couple of my images.

This first photo of one of the lilies in my garden was taken slightly underexposed. By doing this, it looks pretty close to how I expected to see the final image look.

There are a couple of things in the panel to look at. The first is the histogram. You can see that all the histogram data is between the two edges. Go back and watch my video, What is Good Exposure in Photography, to see why this is important and something you should generally strive for in your photos. The second thing that I’d like you to look at is the size of the file, 16.83MB

This next photo is shot using a technique I recommend: exposing to the right. This means the histogram should be as close to the right-hand edge as possible without clipping any highlights. To achieve this, I increased the ISO by 1.3 stops and slowed the shutter speed down by 0.6 stops from 1/800th to 1/500th – I didn’t want to go any slower as there was quite a bit of wind while I was shooting, and I didn’t want to have any blur in the image. This has added two stops of light to the shot overall.

You will probably think this process has overexposed the image, particularly the background. I’m guessing you also think the first shot is “better.”

Check the histogram; there is no clipping on either side, but the data has shifted far more to the right. This technique also increases the file size to 17.89MB—an increase of just over 6% in the data we have collected. 

This proves that the advice given needs to be corrected; evidentially, under-exposing an image gives less, not more, data. The reason for this is the way data is stored in a digital image. Let’s split the histogram up into ten percentiles. The top percentile at the highlights end of the histogram contains 50% of the data. The next percentile has 50% of the remainder, and so on.

As a result, we will always have more data in an image the more we push it to the highlights end of the histogram. The key thing is that we shouldn’t clip highlights; we should only push them as close to the edge of the histogram as possible.

When I edit the lighter image, I can create the result I had in mind with just a few slider tweaks. If I then compare the two images, zoomed into the stamen of the flower, I think you’d probably agree that the image on the left (the one that was initially brighter, now edited) is much sharper—as a result of having more data at the lighter end of the histogram. 

With that long description of exposing to the right, let’s look at how what I believe was bad advice has led to issues in the three photos Frances sent over. This time, I am going to look at the unedited RAW file. 

The first image to look at is the sunset image. I like the composition of this shot, with the figure on the hill sitting on the bottom left third of the shot. They are looking across the scene towards an interesting sky. I like the use of negative space to provide impact. However, despite being shot at a relatively low ISO (250), the sky looks quite noisy. Frances could have possibly reduced the ISO by shooting with a slower shutter speed. Rather than shooting at 1/400th of a second, it could have been slowed down to 1/160th, lowering the ISO to 100. However, the majority of this noise, I believe, is caused by under-exposing and having less data in the image.

The other concern I have is the extent of under-exposing. The histogram below shows a significant amount of clipping in the shadows. If you click on the triangles at the top of the histogram in the Develop module, it shows clipped shadows in blue and clipped highlights in red.

This means that we can’t pull back info from these areas, and as you will see, when I apply a basic edit to the shot, we cannot use the data effectively. 

The edits I used increased the overall exposure but then pulled back the highlights slider to help improve the sky. I opened up the shadows, as I think it’s nice to see a hint of colour in the grass. However, this is where the issue of the clipped shadows comes in—the lack of data means we get a very noisy foreground. I then selected the sky and warmed up the colour balance to help make the sky more dramatic. 

If this had been shot using the expose to the right technique, I think it could be an excellent image that could have easily been manipulated to give a dramatic result. The issues in this shot are more related to the under-expose advice than anything about composition or technique. 

The next image of the crows shows similar issues. Again, the body of the front crow has clipped shadows.

When I pressed Auto in the Develop module, I saw that the focus on the front bird was excellent. The choice of an f/10 aperture is a good one, as Frances is using a longer zoom, which reduces the depth of field in the image. Using a smaller aperture has maintained the depth of field to cover the body of the front bird. I would have liked to see a different composition with the subject moved to the left rather than the current central position. Doing this allows the subject to look across the scene. I would remove the flying bird in the background using the remove tool. Again, there is quite a bit of noise in the darker areas, which I firmly believe is down to under-exposing rather than the ISO. 

The final shot is well-handled in terms of focus and exposure. This time, the shot has less chromatic noise, as the histogram has been pushed a little more to the right. My only criticism in this picture is that it would have been nice if Frances had moved a few centimetres to the left to lift the spider away from the petals behind it. It would also be good to tidy up some of the petals on the frame's edges. Frances might also consider cropping it to a square to tighten up the framing of the image.

Overall, these are good images for someone relatively new in their photographic journey, but some bad advice about underexposing them has let them down. 

I hope that by applying some critique to some of France's images and explaining why I believe that issues have risen, I have convinced you why I refuse to believe that underexposing pictures leads to better photographs.

If you’d like to learn the basics of exposure and composition and live near the beautiful city of Edinburgh or want to come and visit and learn simultaneously, my Switch to Manual workshops run from Wednesday to Sunday. You can find out more information and book here.

I have some great topics lined up over the coming weeks. They include tips on taking better photos, gear reviews, and maybe even ways to save a bit of cash when buying new camera equipment. The best way to see my content as it is released is to subscribe using this button down here. While you are there, give this video a like to help bring a few more people to my channel. 

Remember, I like to keep my video length to the time it takes for a coffee break. Shorter videos are my espresso offering, and slightly longer ones, like this one, are Americano-sized. Very occasionally, I might serve up a Mocca Choco Latte, which will allow you to kick back for a slightly longer break.

My name is Rich Dyson from Edinburgh Photography Workshop, and this has been Coffee Break Photography.