It’s no secret that the Canon 7D, while an excellent APS-C sensor at lower ISO levels, is quite noisy at high ISO levels when compared to other camera offerings. The Fujifilm X-Trans sensors perform excellently at high ISO levels. Even my Panasonic GX7, which is a micro four thirds sensor, performs better. But the 7D is an excellent body with fast autofocus and plenty of great features in the 2.0 firmware that make it a capable camera that I will probably continue to use into the forseeable future. But the problem of noise is something all 7D owners deal with so I thought I’d run a few tests to find out how I can manage that noise since high school football season is coming up quickly and it will soon be time to get the long lens out and start shooting fast shutter speeds, wide open, in outdoor stadiums with crappy lighting.
Since I’ve had my 7D I’ve naively assumed that shooting in full RAW mode at as low an ISO as possible is the only way to get good results. It’s an understandable mistake to make—but it’s still a mistake. I don’t own a 5D body so I can’t test this with other Canon offerings, but it’s clear in my tests that the 7D has different noise patterns at “standard” ISOs than it does at 1/3 of a stop off, and that the MRAW mode (which is essentially a 10Mp interpolated image) is actually better at controlling the appearance of noise in the final image than by shooting at standard ISOs in full 18Mp RAW mode.
I’m not a computer science guy (even though I am a programmer by trade) so I don’t understand all the intricacies of sensors and how they work. I can’t explain to you in engineering terms why this works. I only know that, for my tastes, using MRAW mode on my 7D produces better noise patterns than full RAW. I can still upsize the image to just about any size I want using the Genuine Fractals algorithm in Perfect Resize 8 without making the noise more apparent. Here’s the test I did to prove it to my satisfaction.
The Test Parameters
The test subject is one of my old Rolleicord TLR cameras. I shot it in close with a Canon 17-40L at f4.5 on my 7D. I didn’t need to shoot it at a smaller aperture because I’m more interested in the noise patterns that show up in out of focus areas because that’s the part of my images that concern me most. There’s isn’t a lot of detail actually in focus in these shots but that’s okay. I know I can get plenty of detail at high ISOs and that’s not the part of the image I’m concerned about.
If you research the topic much on the Google you’ll find that the native ISO of the 7D is actually 160 and that the best results can be obtained at that ISO level. So I shot the first scene (on a tripod with cable release) at ISO 160 in both RAW and MRAW modes. I didn’t expect to see much difference between the two at that low an ISO. But I was genuinely surprised to see a noticable difference between the two images in out-of-focus areas. To my eyes, the MRAW images were cleaner. At standard viewing size on a monitor, you can’t really tell much of a difference, which might lead some to conclude that the difference is not enough to be concerned about. For you that may be the case. But keep in mind that there are photographers (myself included) who are never happy with their work and are continually striving for that next little bit of improvement no matter how insignificant it might seem to some. In my experience it’s the little things that matter and that’s no less the case in digital images. Even the OOF noise patterns can affect a printed image at 16x20 and that’s something I care about a whole lot. Not everyone does and that’s fine too. You can see the difference in the screenshot I took of the four images I’m comparing (the last two shots are discussed later and are the same scene but at ISO 12800):
The first image is at ISO 160 in RAW mode. The second is ISO 160 in MRAW mode. The only processing done to them was a Monochrome adjustment in Canon’s Digital Photo Professional (to eliminate any artefacts added by Adobe Camera Raw). I also adjusted the tone curve to “linear” and made other small tweaks to get the images to look as similar in tone as I could given I took them at necessarily different shutter speeds and ISOs. I added no sharpening or noise reduction at all. This screenshot is not a display of converted images but a preview in DPP of the RAW and MRAW files so there are no artefacts of JPG or TIFF conversion either. Long story short: even at base ISO the MRAW files appeared to be marginally sharper, the tones were more pleasing (likely because there was definitely more contrast before I started tweaking them in the RAW converter), and the noise is more pleasing in OOF areas—at least to my eyes.
Taking it to the Max
The real test for me was not just high ISO but as high as the 7D can support: ISO 12800. When shooting sports, I need as fast a shutter speed as I can get and sometimes, especially later in the season when it gets dark earlier, the stadium lights are insufficient to provide high enough shutter speeds at lower ISO levels to stop action and keep things sharp. I often have to shoot above ISO 3200 just to get action reasonably sharp.
I took a number of test shots and performed the same tweaks on the ISO 12800 shots as I did the ISO 160 shots. The noise was obviously much greater at max ISO but, to be honest, doesn’t to my eyes exceed that of film pushed to ISO 1600 (which I still shoot, though mostly in medium format). I mostly care about B&W because that’s what I specialize in so the fact that the colors of an ISO 12800 shot are slightly off doesn’t make any difference to me. If you shoot color at high ISOs, though, just be aware that you’ll have to do some desaturation and get a decent profile created that you can apply en masse to your images to make the colors near acceptable.
In the last two comparison images, you can see a clear difference between the RAW image (number 3) and the MRAW image (number 4). At ISO 12800, the MRAW image is, to my eyes, clearly superior to the full RAW image. The detail is sharper and the OOF noise is much more pleasing than the noise produced at full resolution at ISO 12800. It’s a bit complicated why this is the case but it has to do with how the 10Mp MRAW image is created from an 18Mp sensor. The interpolation that’s done to the sensor data to get a full-size 18Mp image is actually detrimental to the noise patterns at high ISO. When shooting in MRAW mode, you’re reversing that process and eliminating much of the accentuation of the noise pixels by doing a noise reduction algorithm that’s much more effective when applied at capture time rather than at post-processing time.
Although the last two images in the above screen shot have no noise reduction in them, the Canon DPP program does do a very good job of eliminating chrominance noise in high ISO shots. I use Lightroom for most things but I’m seriously thinking I might actually change my workflow a little to include pre-processing my RAW images with DPP. The settings will carry over into Lightroom and I get the benefit of a little better control over the RAW conversion than what I can get out of just Lightroom by itself.
You will loose detail by adding luminance noise reduction to your high ISO shots. There’s no way around it. So what is luminance noise? First, understand that chrominance noise is off-color pixels in a high ISO image. Those noise pixels don’t match the color of the surrounding “real” detail pixels. Adding chrominance noise reduction to a RAW file through DPP doesn’t cause a loss of detail or smudginess—it just makes those off-color pixels less apparent. Luminance noise reduction, however, is the kind that creates smudginess when applied to excess. In simple terms, it tries to average out a pixel value by looking at the surrounding pixels and trying to determine if it is too light or dark a value. This isn’t a huge issue in shadow areas as the noise pixels will be darkened to be closer in value to the surrouding shadow pixels. But when you get into mid-tones, luminance noise is very apparent and if you apply noise reduction too aggressively, the pixels representing detail will get confused with noise pixels and, while the noise pixel value will be adjusted to more closely match the surrounding pixels, the actual detail pixels will also be adjusted. This is what causes the smudging. I’ve found that a really good noise reduction algorithm like that found in DxO Optics Pro 9 does a fantastic job of reducing luminance noise. The “PRIME” algorithm in DxO is superb—but it takes several minutes of maxing out your CPU to achieve the results it does. Save that for your most important shots.
From now on, I’m shooting MRAW
You may not be a hardened pixel-peeper or have photographic OCD when it comes to image IQ. Most modern cameras, whether they have 1-inch sensors or full frame, are great image capturing devices so you can get a great image without obsessing over post-processing. Cameras these days can capture images in lighting conditions that we never could have with film. We’re really particularly spoiled with the plethora (“would you say I have a ‘plethora’ of pinatas?”) of options when it comes to sensors and capture devices.
But sometimes you really want to go a little further to eek out a little more IQ from your images. Sometimes you’re shooting in conditions that others would never attempt. That’s when these little tricks, like shooting MRAW on the 7D to get better results out of high ISO images, are necessary. They seem unecessary until you need them. But when you need them, you really need them.