Tuesday, April 20, 2010

Camera shake and motion blur, be damned!

Camera shake and subject motion blur have become a little bit of an issue for me lately when shooting with long focal lengths on my new Canon 7D. I’ll explain why further down in this post, but suffice to say that the reason surprised me.

Camera shake is precisely why I buy and use Canon Image Stabilizer (IS) lenses or use a tripod whenever I can. All manufacturers have a different name for their image stabilization technologies, but they all have them.

There is absolutely no doubt that IS lenses improve the sharpness of all of my photos. If you have any doubt about the capabilities of this great lens technology, try them for yourself to see the difference. Buying IS lenses is worth every penny of the extra cost.

I thought I had a pretty steady hand-holding technique, but when I see my hand-held IS images versus my hand-held non-IS images on a computer screen, the difference is clear. The images taken with IS are always sharper. Maybe I drink too much coffee that causes me to be jittery??!! Maybe I just need to improve my hand-held shooting technique a little bit…

But even with IS, some issues with camera shake and motion blur are still around. The point of this post is to make people aware of a simple factor that might be playing into your photography.

So what surprised me?

The APS-C sensor is the type of imaging sensor used in almost all DSLR’s except the pro level models.

Camera shake and subject motion blur are magnified even more on higher megapixel APS-C chips (e.g., 18 megapixels) than they are on lower megapixel APS-C chips (e.g., something like 12 megapixels). This is something that I was previously unaware of. Even Canon states this in their own technical white paper documentation.

In other words, as you go up in megapixels on an APS-C sensor, steadying your camera and using higher shutter speeds to prevent subject motion blur become increasingly important to achieve sharp photos.

The above statement from Canon (which applies to other manufacturers as well) is one of the reasons that I’m against pushing APS-C sensors up toward 20 megapixels. I think it creates many more problems than it solves and most people would be happy with 10-12 megapixels on an APS-C sensor in a DSLR. But camera manufacturer marketing mayhem prevails, and I can only expect the megapixel ratings on APS-C sensors to continue to increase because they think it’s “what the people want”.

So what does this mean in everyday use?

Well, for me (and I suspect other people using other cameras in the megapixel class of the 7D) it means that I can no longer reliably handhold a lens like my Canon 70-300 when it’s zoomed all the way out to 300mm using previously appropriate shutter speeds. On the 7D, the 300mm end of that lens is really 480mm due to the 1.6x crop factor of the APS-C sensor. Combining that long focal length with the 7D’s 18 megapixel rating on the APS-C chip, and suddenly I have a problem with camera shake and motion blur that I never had before on my old 8 megapixel Canon 30D camera. Nothing with me has changed. The problem is that it’s technically inherent that higher megapixel APS-C cameras magnify the effect of camera shake and motion blur more than lower megapixel APS-C cameras. Bummer!

So what can you do about camera shake and motion blur on high megapixel APS-C cameras?

1) Shoot at higher ISO’s so you can raise your shutter speeds even farther than you normally would...

2) And/or use IS lenses or a tripod...

3) And/or improve your hand-holding technique...

4) All of these things...

The basic point is to get the shutter speeds way up and steady the camera with IS or a tripod when you're shooting in conditions that may result in camera shake or motion blur with a high megapixel APS-C camera.

Moral of the story: Don’t be too quick to blame a camera’s auto focus system or a lens if your hand-held images are frequently blurry. I read posts on camera web sites from people complaining about the blurriness of their hand-held photos all the time. These days, it might very well be caused by a combination of your hand-holding technique and shooting on an APS-C camera with a high number of megapixels.

Try the four points listed above and see if your images get sharper. I bet they will!


  1. Interesting information, thanks for taking the time to write this. I can't help but wonder if taking smaller image sizes would make a difference. I mean if don't need an 18 megapixel sized image then, why not go to a smaller size? Would that lessen the effect of camera shake?

  2. Hi Charles...

    No, taking a smaller photo/file size using more JPEG compression on the same 18 meg sensor wouldn't solve this problem because you're still using all of the 18 megapixels on the sensor to take the initial photo, you're just compressing the data more after the fact in the camera before the image gets written to the card to get the smaller file size.

    Basically, this issue is tied to the size of the pixels on the sensor. Specifically, the surface area of the pixels. I read a great explanation of why this is on the web a few weeks ago but I didn't note where I saw it. I wish I had bookmarked the page.

    Basically, take a large pixel surface area from an APS-C sensor with low megapixel count and a small pixel surface area from an APS-C sensor with a high megapixel count.

    Considering the surface area size difference of those two pixels, the same amount of relative movement across those different sized pixel surface areas will allow the motion to get farther across the smaller pixels than it will get across on the larger pixels. This leads to more motion blur sensitivity on the high megapixel APS-C sensor because the smaller pixels are "seeing" more movement across their surface area.

    People reading back my explanation might not be able to make heads or tails of what I'm trying to say here, but since I read that other article my explanation above makes sense to me. :-)

    I will try to track down the article I read and post it here. It really clarifies the physics of what's involved with high megapixel APS-C sensors.

    In addition, Canon has acknowledged all of this in their white papers, so it's a known "issue" of high megapixel APS-C sensors.


  3. I own Canon 50D camera. I wish I have the same features on 8 or 10 MB camera!! I and other consumers don't need 15 MB photos!!

  4. Hi Salah,

    I totally agree. I wish they made the 7D as a 12-14 megapixel camera instead of 18 megapixels. I don't need 18 megapixels either, but I wanted the features so I got it...


  5. Where has canon acknowledged this?

  6. Hi Dana,

    It's alluded to at the bottom of page 35 in this Canon guide:


    ...where they say the following (commenting about the high megapixel rating of the sensor):

    "When an AI Servo AF photo of a moving subject is viewed on a computer display and the photo seems to be slightly unsharp, it is incorrect to assume that a focusing issue is always the cause of the problem. Even in photos shot with a fairly fast shutter speed, the lack of sharpness could be a result of subject movement or camera shake. This is particularly relevant to the EOS-1D Mark IV because even small levels of motion blur are noticeable at 100% magnification due to the camera’s 16.1 megapixel resolution. First, determine whether the sharpness problem is caused by poor focusing, camera shake or subject movement. If it is camera shake or subject movement, an effective countermeasure is to use a faster shutter speed. Up to now, if you thought increasing the shutter speed by one stop was sufficient to eliminate motion blur, try increasing the shutter speed by two steps and then shoot the photo".

    I also read another article (but don't remember where I saw it) about the physics of this situation.

  7. John,

    Thanks for the first unbiased post I have read on this subject. It really makes sense to me being a novice photographer trying to figure out why my pictures were better on the 40D. I will try the tips given, thanks for the advise.