Assignment, Week 2: Shake reduction methods
Theme: Stillness of Night
While we didn't have a chance to go through all of the photos from Week 1, one of the chief problems you may have encountered in low-light situations is image blur. Generally, blur is caused by inconsistency in where light falls onto the sensor - this might be caused by the sensor itself moving and changing its position in space, or by the subject itself moving, and thus changing where the light falls onto the sensor.
We'll focus on blur due to camera shake first. There are basically three degrees of freedom - three ways that you can "shake": rotationally (pivoting around the camera's center), laterally (side-to-side, or up-down), and fore-aft movements (shifting the camera forward and backward). You can see a more rigorous definition in the powerpoint presentation, but in most cases the lateral and fore-aft movements are negligible in comparison to the rotational movements, and thus we can focus on the rotational shake, which can be boiled down thus:
As can be seen from this equation, the amount of blur you get (the unit for the above is image lengths, or blur as a % of the entire image) is a function of three things: average rotational speed (how fast you shake), exposure time (shutter speed), and angle of view (a function of focal length and the crop multiplier of your sensor). This jives with conventional logic - if we shake the camera faster, we get more blur. We tend to get more blur with longer shutter speeds. And if you use a larger angle of view (when you "zoom out"), you tend to have less blur. An important point to note is that each of these factors are multiplicative, rather than additive - zeroing one will zero the total amount of blur. So if you had a zero rotational speed, it doesn't matter how long your shutter speed is, or how narrow your angle is - the blur will be zero. Similarly, with an extremely fast shutter speed (say 1/10,000s - close enough to zero), we also zero the blur, no matter how fast we shake the camera.
There are several methods you can try out to reduce the amount of blur in your photos. This week will focus on the rotational speed factor - basically, ways to shake the camera less.
- Second shot: You might notice that whenever you fire a shot with your camera, pressing down on the shutter button exerts a force on the camera, which displaces its position a little bit, creating blur. By setting the camera into a "continuous shooting" or "burst" mode, you can take multiple shots at a time, and on average, shots after the 1st one will be significantly sharper because there isn't a deliberate shutter-press force exerted.
- Breathing method: When using firearms, there are a number of different breathing techniques in order to aim and fire the gun steadier, and these techniques readily apply to photography as well. One common tip is to fire while exhaling, as your body tends to be more still at this point.
- Multi shot: Like a lot of things in nature, the amount of blur you get in each shot isn't a constant amount, but will vary from shot to shot. While you might *average* a certain amount of blur, some shots will be blurrier than the average, and some will be sharper. Thus, you can use probability to your advantage - with a large enough sample size, you will eventually get *one* image that is acceptably sharp and blur-free, and that's all that matters, even if you're throwing away 99 other shots that are all blurry. This is useful technique that one couldn't really practice with film, but is now viable with digital since it costs nothing to record and discard an image.
- Angle of view: As shown by the formula above, the angle of view also determines the amount of blur. By using a wider angle, your image will get less blurry - instead of standing far back and shooting from a distance, zoom your lens to a wider angle and move closer to the subject.
- Improvised tripds: As some of you discovered in Week 1, a tripod doesn't always have to be a tripod - virtually any inanimate object will do in a pinch, so you can use any ledge or table or column as a stabilizing base for your camera. Another interesting do-it-yourself piece of gear is what's known as a "string tripod", which I could describe here in words but is perhaps better explained in this video:
If you want to try making one, all you need is a bolt, some string, and maybe a washer or something for you to step on. The size of the tripod mount is a 1/4", 20 thread size - just take your camera down to the hardware store to make sure you're getting the right size. I believe the ACE hardware store on University sells them for 19 cents or something.
- Image stabilization technology: We didn't really talk about this one in class, but many cameras and lenses today have image stabilization systems - Nikon calls theirs Vibration Reduction (VR), Canon calls it Image Stabilization (IS), Sony calls it SuperSteady Shot, and the names just get more bizarre from there. In any case, all of these technologies esentially have a shifting lens or sensor element that compensates for movements from your camera shake, thereby correcting the displacement and inconsistency.
For this week, the assignment will be a test of one of the methods (second shot, breathing, angle of view, or improvised tripod) outlined above. Take a few shots (~10) as you normally would, then take a few shots using one of the shake reduction methods. For each set, count the number of shots that came in "acceptable sharp" (your criteria), and post your results in the forum:
http://www.photodecal.org/forums/viewtopic.php?pid=62
You may also try the multi-shot method, in which case you'll take as many shots as you need to get an acceptly sharp shot, report that number (good shots/shots taken), then post the sharp shot and another shot typical of the average blur you got in the gallery.
There is no set photo assignment for this week, but if you'd like you can post what you shot in the gallery, and we'll have a photo review. My general idea is for you to push the limits of your photography skills in dealing with blur - "zoom in" to super-long focal lengths, and take long 1s, 2s exposures in the dark, where you'd typically get insane amounts of blur, but see if you can utilize the shake reduction techniques discussed above to come out with a usable shot. From now on I'll also introduce a theme with each week - just a little theme/motif you can base your photos around, if you'd' like. The theme for this week is "Stillness of Night".
Assignment summary
- Try out a series of about 10 shots in low-light situations, using fairly long shutter speeds, then shoot another series of shots using one of the shake reduction methods described above (you may also test out the effectiveness of your camera/lens' image stabilization system). Post your results (good shots/shots taken) in the discussion thread.
- You may also try the multi-shot method - in this case take a huge set of shots continuously (10-20 shots), and post the results (good shots/shots taken) in the forum. Then post the best shot, and an average-type shot in the week 2 gallery.
- (Optional) Try taking low-light photography to the extremes - "zoomed in" to long focal lengths (narrow angles of view), and using extremely long shutter speeds. Post a shot with how much blur you'd typically get, and post a shot of the best you could achieve using one or more of the techniques (list which ones you used). There's an optional theme, "Stillness of Night", that you can follow. Gallery link
