Seeing Red and Loving It: Mirrorless vs DSLR for Infrared

If you’ve been following my photoblog of late (see on 500px, Facebook, or my own site), you know that I’ve been doing a lot of experimenting with infrared photography. I’ve finally settled on a camera that I really like and in this article, I’ll share some of the things I’ve learned along the way. 

Why Infrared?

Funny you should ask. Have a look at these images I’ve created over the past couple of years:

I enjoy IR because it lets me create contrasts in scenes that wouldn’t otherwise have them.

I enjoy IR because it makes high-noon — especially when it’s hot outside — a fabulous time to make images.

So, if you’re similarly interested … here are some of my thoughts about the process:

Suggestion: Rent Before You Buy

This is not bad advice even for visible-light cameras, but I think it’s especially relevant when you’re working with infrared. I rented three IR-modified cameras before I finally pulled the trigger and bought one. I’ve rented from both BorrowLenses and LensRentals and had top-notch experiences with both.

Observant readers might note that I said something on Twitter around Labor Day about a failed camera from LensRentals. Turns out the shutter had a massive failure either during shipping or immediately upon arrival. What I should have mentioned soon after, but didn't, is that they were extremely responsive and had a new camera to me in time for the trip I was taking. Very impressed.

As of this writing, it looks like BorrowLenses no longer carries IR-modded cameras; LensRentals has several.

DSLRs Can Be Challenging for Infrared

I’ll admit it: I’m a creature of habit. I’ve been shooting for more than 20 years now. I started with Canon SLRs (well before digital became commonplace) and I’ve stayed with Canon to this day. My main workhorse camera for visible-light photography is a 5D Mark II.

So you can understand why my first instinct was to try IR-modded Canon bodies. I have tried a Canon 5D (original) and a 5D Mark III on various recent trips, and while I came away with images that I like, I also wound up with a lot of images that were technically flawed — badly underexposed, badly focused, or sometimes both.

Why? I think it has to do with how DSLRs are constructed and the physics of infrared vs visible light. Remember that in a DSLR, the sensor is used only for recording the final-form image. In general (yes, there are exceptions), a separate mechanism is used when you ask the camera to help with focus and exposure. The light that is driving that decision is reflected — at an angle — by the mirror, away from the image sensor.

When you are shooting with an unmodified camera, you don’t typically think about that because the camera’s focus and exposure sensors are tuned to read visible light and respond appropriately. But when the sensor is modified for infrared, the exposure meter and focus mechanism are not modified, so they are still reading visible light.

This means auto-exposure is likely to underexpose significantly. One to two stops is typical in my experience, but that may vary wildly based on the scene. Since you are still seeing visible light through the viewfinder, it may be difficult for you to anticipate the extent of that underexposure.

Focus is even more likely to be in error. Remember how light splits into its various color components when it passes through a prism? (For example: sunlight + rain = rainbow.) This also happens as light is guided through your camera’s lens and mirror. Infrared light will focus at a different point than visible light, but a DSLR camera’s focusing mechanism isn’t necessarily tuned for the infrared focus point. (For more detail, see LifePixel’s tutorial on infrared photography, especially the section titled “How light waves focus at different points.”)

Most DSLRs, when modified for infrared, will be adjusted to focus correctly when used with a 50mm lens, but at other focal lengths are prone to focus errors. Speaking from experience shooting with zoom lenses on the Canon bodies I used, it’s very easy to forget to reset to the “correct” focal length and very difficult to guess at the correct focus compensation when you’re in that situation. A lot of my failed images were due to focus issues that I don’t experience often when shooting with my normal Canon body.

I had thought for some time that I would buy a second Canon body and have it modified for infrared, but after my two rentals, I lost confidence that I would be satisfied with that as a long-term plan.

Edit: A common thought among photographers is to take an older DSLR body that they wouldn’t otherwise be using and have it modified for infrared. Before doing that, please remember that infrared generally cuts 1-2 stops from your available light. Older sensors are typically not as good at handling low-light situations. If, like me, you prefer to shoot mostly handheld, that may mean your older DSLR is going to give you images with more grain or more motion blur than you’d like after the modification.

So Maybe Mirrorless?

Having heard friends speak highly of mirrorless cameras for visible light photography, I decided for my most recent trip that I should seek out an IR-modified mirrorless camera.

My theory was that, since mirrorless cameras use the same sensor for exposure and focus decisions as for the final image, the problems I described above would go away. So, to test that theory, I rented a Sony a7R modified for 720nm infrared from Lens Rentals.

Long story short: My theory was right. I took this camera with me on a two-week roadtrip through the southwestern desert US and it performed very, very well.

As a mirrorless skeptic, I have to say I’ve been impressed with the quality of the lens and sensor. 36 megapixels and the images are sharp, even at 1:1!

Here are some samples from this trip:

I liked the camera enough that I bought it from LensRentals. (As of this writing, they have a new one available for rental again.)

For the curious, I’ve since learned that the IR modification on my camera was done by Kolari Vision. I’ve also heard good things about the conversions done by LifePixel, but I don’t have any direct experience with them.

I’ve still got a nice backlog of images from this trip to work up and post, and I look forward to shooting and sharing more.