So, this serves as a “little” addition to last night’s post about blur. Here, I’m focusing specifically on the effect of aperture on background blur. Remember that the same idea applies to foreground blur, as well.
I put together this little animation to demonstrate the effects of aperture changes, as well as how I compensated for the changes in light.
Notice that, aside from the first change, each change in aperture requires half as much time to compensate in light (that’s called a stop, again, another blog). Also, notice how the foreground plant stays sharp throughout, the mid ground plant comes into focus around f/8, and the log in the background isn’t really sharp until f/22.
The foreground plant was about 2 feet (0.7m) in front of me, the midground plant about 3 feet (1m) in front of me, and the log laying behind them something like 8-10 feet (3m) back.
In the next animation, you’ll see what happens when you don’t compensate for the change in aperture.
It got so much darker that I had to add a box to make sure the text was legible… Which I probably should have done for the first animation…
Now… It’s time for some science. These instructions are written for someone who doesn’t have a whole lot of experience with their camera yet, but can work their way around the settings alright. If you don’t yet know how to work the settings in manual mode, this experiment will be a great way to learn what the fancy numbers actually do. Consult your manual if you aren’t familiar with what buttons do what, or just… play with the buttons until stuff happens, that’s how I learned.
What You’ll Need
- DSLR (or film SLR if you’re nuts… like me) with lens, preferably a prime lens (zoomless), but any lens will do as long as you stay at the same distance and focal length (zoom). I’ll be basing instructions on the use of a 50mm lens on a crop-sensor DSLR (like a Canon Rebel).
- A Tripod! You could attempt to hand hold the camera through the experiment, but the slowest shutter speed you should attempt to hand hold at is probably 1/60th of a second. 1/30th if you’re really steady, and maybe 1/15th if you’re a trained sniper.
- A working knowledge of how to adjust your camera’s settings in manual mode.
- A still (or almost still) subject, with a fair amount of background behind it! If you’re shooting a vase with a wall directly behind it, you’re not going to notice too much of a change. That doesn’t mean you have to shoot outdoors for this experiment, though.
- Start by getting your camera mounted to your tripod and placing it something like 1.5-3 feet (.5-1m) away from your subject. The closer you are to your minimum focusing distance, the more drastic the effect will be.Steps 2 and 3 can be done in either order.
- Set your aperture to f/22 and compose your shot. Again, make sure you have plenty of background content at varying distances from you and your camera. (Shooting at an angle to a flat surface is another great way to demonstrate aperture blur!)
- In Manual mode, set your aperture to the closest “normal” aperture to your maximum (remember, max aperture is the lowest number). I’ll include a list of the standard apertures below. Set your shutter speed to either 1/60th of a second. Now pick an ISO that allows for a good exposure; you can do this by eye using live view on a DSLR, or by using your light meter in either a digital or film SLR. Unfortunately, if you are using an SLR, my specific guidance is going to end here, and you’ll have to adjust with only shutter speed and use the tables below to complete the experiment. I don’t normally suggest adjusting your ISO over it’s minimum or your camera’s natural ISO, but things would get very complicated to explain, otherwise.
Now make sure autofocus is OFF, focus on your subject and you’re all set up!
Performing the Experiment
Make sure that you’re writing down all your settings if you’re using an SLR. If you’re using a DSLR, your camera saves all that in your metadata as long as you’re using a compatible lens. If you’re not, then note your aperture for each exposure.
If you’ve set everything up as I’ve instructed, then your exposure settings for each shot should look like the following: (apertures in parenthesis are for lenses with a lower maximum aperture, an ‘X’ means that you probably won’t be able to decrease your aperture further)
E1: f/2.0 (f/2.8, f/4.0) at 1/60th of a second
E2: f/2.8 (f/4.0, f/5.6) at 1/30th of a second
E3: f/4.0 (f/5.6, f/8) at 1/15th of a second
E4: f/5.6 (f/8, f/11) at 1/8th of a second
E5: f/8 (f/11, f/16) at 1/4th of a second
E6: f/11 (f/16, f/22) at 1/2 second
E7: f/16 (f/22, X) at 1 second
E8: f/22 (X, X) at 2 seconds
Now, examine your results! Feel free to send them my way and I’ll feature them in a follow up posting with your permission. Also, as always, feel free to get in touch with me if you have any questions, comments, concerns, or noticed that I buggered something up.
Now, for the data tables! There will be plenty more info on these to come, as well as variations on this and my last post that specifically delve into each aspect of the “Exposure Triangle” as well as focal length, sensor size, and more to come; so if this information doesn’t mean anything to you now, don’t worry!
(+: Standard Aperture, -: Partial Stop. From one Standard Aperture to the next, or equidistant, is one full stop of light, or 1/2 of the light hitting the sensor)
(Most Light, Narrowest Depth of Field)
(Least Light, Widest Depth of Field)
(+: Standard Shutter Speed, -: Partial Stop. From one Standard Shutter Speed to the next, or equidistant, is one full stop of light, or 2 times of the light hitting the sensor)
(Fastest Speed, Least Motion Blur, Least Light)
-1 3/10 (1″3)
-1 6/10 (1″6)
-2 1/2 (2″5)
-3 2/10 (3″2)
B (Bulb/Button, press and hold or use a trigger mechanism like (TriggerTrap!) for extended exposure times)
(Slowest Speed, Most Motion Blur, Most Light)
(Note that ISO speed, or the sensitivity of your camera’s sensor or film to light, works in the same way as the above, in stops. Some cameras may have partial ISO stops, but mine does not, and most entry level DSLRs will not, so I’m going to give you only the full standard stops.)
(Least Light, Least Grain)
(Most Light, Most Grain)
If your camera goes over 12,800 ISO, or if you have a lens that actually goes down to f/1.0 or lower, or if you have a camera that will shoot faster than 1/4000th, then I don’t know what the heck you’re doing reading a basic tutorial like this; and also please donate to my “No more crop sensor camera” fund.