Okay - most of this is out there in other forms, but I thought I'd take a moment to gather all of this information together in one easy-to-find posting. The Rebel T2i is a fantastic camera for the price, and a good camera regardless of the price for shooting motion images. However, if you are new to the world of DSLR's, and have only shot full-auto on most camcorders, here are a few basic things you need to understand, especially if you want to shoot "film-like," narrow depth-of-field images, and play with focus.
Aperture. also referred to as
f-stop. This is the number on the lens of the camera that usually looks like f/3.5, or a range, like f/3.5-5.0. The thing to know is that the lower the number, the wider the aperture, and the narrower the depth-of-field will be. On a nice lens, the f-stop is a single number. On a cheaper telephoto lens, the f-stop has a range, and the first number is the f-stop at the widest angle, and the second number is zoomed all the way in. To get that really narrow depth-of-field, you want to be shooting at an f-stop lower than f/4. F/2.8 looks really nice, and is probably a good, practical number for motion shots. I've been experimenting with f/1.4, and it's fun, but a bear to keep moving people in focus.
Shutter Speed. This represents the time the sensor is "exposed" to light each frame. The number in the viewfinder usually looks like a number between 30 and 4000. "30" means 1/30th of a second, and "4000" means 1/4000 of a second. High numbers mean no motion blur in a frame, which is great for sports photography, but doesn't look like motion picture film. Lower numbers provide some motion blur, which we want to get that film-like look. Normally, 24fps feature film is shot at 1/48th of a second. The only exception to that rule is typically found in Ridley Scott action sequences - go watch the opening battle of "Gladiator," or look for it in many scenes in "Blackhawk Down." You'll see scenes that have a very "stuttery" appearance, like the motion is faster than it should be, but it's not sped up. The shutter was running at 1/125 or 1/250th of a second in the camera, creating that "look."
ISO. This is the sensitivity of the chip in the camera. Lower numbers mean less sensitivity to light. Higher numbers mean more sensitivity, but typically higher noise. You'll hear discussions about the best "usable" ISO, meaning where does the noise become unacceptable. In daylight, numbers like ISO 80-200 are talked about, while shooting indoors, or at night, you may have to go as low as ISO 6400.
To get that "film-like" look, you need to be aware of all 3 values while you shoot. Ideally, a wide aperture, low ISO number, and a shutter speed that mimics film would be ideal. But, let's talk specifics to the T2i.
First off, the kit lens for the T2i does not have the right range of f-stop to easily shoot what we want. Go and invest in a better lens. If you're on an extremely low budget, grab Canon's 50mm f/1.8 prime lens. It's enough to get started. I splurged a bit and got the next step up - the Canon 50mm f/1.4 lens - it's about $350, but is built much nicer.
Unfortunately, the T2i does NOT have a 1/48th shutter speed setting - it jumps from 1/30th to 1/40 to 1/50th. I've been playing with going from 1/40th to 1/50th, and I haven't made up my mind yet. But, this is the range we want to play in.
The ISO range when shooting moving pictures in the T2i is locked to a range of 200-6400. ISO 200 is where I typically start. This is fine for brighter indoor sequences, cloudy, shady days, dusk, etc. You may go to a higher sensitivity, like ISO 800 or 1600, depending just how dark it is. Just keep an eye on the noise. Different people have different thresholds for noise. I'm amazed just having the option to go to ISO 6400. This camera still shoots decent images at that level. However, noise-wise, I'd prefer to shoot at no higher than ISO 1600.
Here's the first big problem you'll face - ISO 200 is TOO SENSITIVE when shooting in full daylight. Ideally, we'd need to drop to ISO 80, but that's not an option on the T2i. At ISO 200, 1/50th shutter speed, and f/2.8, in bright sun, everything will be extremely blown out.
How do we solve this problem? Well, in-camera, the only solution is to increase the shutter speed - jump the number up until the amount of light in the image looks right. For bright daylight, that could be as high as 1/4000 of a second!
Unless you like the "Ridley Scott action sequence" look, you'll need to invest in another item - a Neutral Density filter, or ND filter.
An ND filter is like sunglasses for your lens - it screws into the front of your lens, and evenly lowers the amount of light that gets in. These come in a range of density - the higher the number, the less light gets in. I have a 0.9 ND filter, and it helps a bit, but it's not enough for full daylight - you need at least 3.0, maybe up to an 6.0 ND filter to shoot broad daylight. I just ordered a couple
kits of filters here, and I'm hoping to stack them and find the right value I'll need.
Another, slightly more expensive option, is to use a
"Dial-an-ND filter" like the one sold here. 2-8 stops is definitely enough for all daylight situations.
Be wary of cheap ND filters - they all affect color in some way (even though they are supposed to be neutral) and you may end up with an unwanted green cast to your video. Invest in good ND filters.
