Digital SLR Photography
Last update: 1/22/05
The following are my notes about digital photography, some are general,
other are specific to the Canon Digital Rebel (300d). If you are
going to buy a dSLR, be ready to spend some money. SLR's are alot
of fun, but they
are expensive. But the payoff is huge amounts of creativity. With
a SLR you can do almost anything. Remember, these comments are about dSLRs,
not P&S (Point and Shoot) cameras, and almost entirely about the
Canon equipment that I have.
Ok, first, some definitions:
- SLR: Single Lens
Reflex camera. When you look thru
the viewfinder, you are looking thru the camera's lens. This is
different from P&S (Point and Shoot) cameras because you are
looking thru the main lens, not the viewfinders lens. It is also
different from a digital camera using the LCD because LCD's don't
capture what the camera's lens really sees (the SLR is optical, LCD's
are usually low resolution). On a SLR you can't use the LCD on
the back of the camera because the mirror is in the way and you are
supposed to use the optical viewfinder.
- dSLR: Digital SLR.
Before digital cameras, there were film
SLRs (which are still popular). The little "d" simply implies
that the camera is a digital camera vs a film camera.
- This page will be using 35mm film as the standard to compare
everything against. There are other formats such as medium format
(120 film, 4 inches wide) and large format (don't know), but in the SLR
arena, everything is measured against 35mm (basically, the
"Standard").
- Most dSLR's have a
"multiplication" factor. This term is
really incorrect, but it's become common. What it really is, is a
crop factor (It cuts
off the edges). It means that a dSLR
can only capture a smaller part of what the lens "sees". This is
because the digital sensor is smaller than 35mm film (the
"standard"). So, for my Canon Rebel, this means that I have
a "multiplication" factor of 1.6. This means that a 50mm lens
(the "standard 35mm" "portrait") lens becomes a telephoto lens (50 x
1.6 = 80). This is great if you like telephoto pictures and
horrible if you like wide angle pictures.
-
 |
The digital camera sensor
size is smaller than 35mm film so it crops the picture (in comparison
to the 35mm standard). This has the effect of making lenses seem
like telephotos, or seem longer than they really are (thus, the
multiplication factor). The Canon Digital Rebel's sensor size is
22.7 x 15.1mm with 6 megapixels.
By the way, P&S camera's sensor sizes are a fraction of this size,
usually around 3mm or less. Big sensors are better, but their
cost increases exponentially. Canon's "full frame" (full 35mm
sized CMOS sensor) digital
camera, the 1Ds, cost over $8000.00USD!!
|
- Telephoto lens: Magnifies
the image. Like a telescope.
(greater than 50mm (in 35mm terms)).
- Portrait lens: 1 to
1 magnification. (50mm, for 35mm film). For the Canon
Digital Rebel, with a 1.6 crop factor, it is a 31mm lens (50/1.6 =
31.25)
- Wide angle lens: Less
than 1:1 magnification (less than 50mm (for 35mm film), or less than
31mm for the Canon Digital Rebel) (I
guess that you could call this negative magnification)
- DOF or DOV: Depth
of Field or Depth of View (how much the
background is blurred)
- Prime Lens: Prime
simply means that it's not a zoom lens,
it's a fixed focal length lens. Usually, a prime lens is much
better than a zoom lens at it's particular focal length (i.e. a 50mm
prime is better than a 28-135mm set at 50mm). Since the prime is
totally designed for it's focal length, it's sharpness and contrast
will be better than a zoom (variable focal length). Of course, a
zoom is much more versatile so it's your call if a prime is worth
it. Personally, I only have 1 prime, the Canon 50/1.8, because it
was really cheap and it's really fast (I can use it in really low
light conditions without a flash)(The 1.8 is the maximum aperture and
indicates how fast the lens is, or the least amount of light required
to get a good picture). High "f" numbers for a lens are bad,
however, lower "f" number lenses will cost you ALOT! The
difference between a Canon 50/1.4 (f 1.4) and a Canon 50/1.8 (f 1.8)
lens is $220USD! ($300 vs $80).
Ok, how much does all of this cost (in 2004 dollars)? I have a
Canon Digital Rebel that I bought with the 18-55mm kit lens. This
is what I have bought so far, in the order that I bought them:
Canon Digital Rebel w/18-55mm EF-S lens:
$999.50USD
Canon EF 75-300 f/4-5.6 EF III
USM
: $170.00 (used)
Canon 550EX
flash
: $350.00
Canon 28-135/3.5 - 5.6 EF IS
USM
: $420.00
Canon 50/1.8
EF
prime
: $80.00 (best value of all
Canon lenses)
Canon 420EX
flash
: $199.00 (wireless slave to
my 550EX)
Canon 10-22mm/3.5 - 4.5 EF-S
: $800.00
TOTAL:
: $3018.50 (not including shipping and taxes; prices
in 2004 USD)
"Short", or wide angle lenses are surprisingly
expensive. It seems
that they are very hard to make. This really stinks for digital
SLRs because of the "multiplication
factor". My 10-22mm lenses
acts like a 16-35mm lenses (in terms of a 35mm film
camera). There is no way to get less than 10mm
(16mm)! Interestingly, my 10-22mm lens is as big as my 28-135mm
lens, focal length has nothing to do with len's size!
Note: EF-S (note the "-S")
lens can only be used on the the Canon 300D and 20D cameras
because their back element goes further into the camera than other EF
lenses. However, any EF lenses will work on any Canon SLR camera
(made in the last 20 years, FD lenses will work (sort of) with an
adapter and in
manual mode).
Aperture (Using my 50/1.8 lens which has the largest range of all of my
lenses):
Biggest opening
Most light
Smallest DOF
Fastest shutter |
f/1.8 f/2.0 f/2.2
f/2.5 f/2.8 f/3.2 f/3.5 f/4.0 f/4.5 f/5.0 f/5.6 f/6.3 f/7.1 f/8.0 f/9.0
f/10 f/11 f/13 f/14 f/16 f/18 f/20 f/22
|
Smallest opening
Least light
Greatest DOF
Slowest shutter
|
Smaller aperture means greater depth of view (the things in the
background are in focus). Portraits are usually taken using a
shallow DOV, which means a larger aperture (low f number).
Landscape pictures are usually taken with a large DOV which means a
smaller aperture (high f number). Isn't it crazy how the f
numbers are the reverse of what you would think they should be, I guess
that it's because they are really a fraction, ie, 1/f number.
Note: For most lenses, around f/8 is the "sweet" spot. Most
lenses work best (best color, sharpest picture, good DOF, etc.) at
f/8. Also, DOF is a big issue (at least for me). At low
(f/1.8 - f/8) big apertures, if I use my 50mm lens at f/1.8 it seems
like everything is out of focus except for my subject's face (this
could be good or bad depending on what you want). Of course, at
f/1.8 I might not have to use a flash or be able to use a faster
shutter, so everything is a trade off and it depends on what you want.
Flash
Built in flash: Never use
the built in flash unless you have no
other choice. When using anything other than the 18-55mm or 50mm
(or physically shorter)
lenses you will get weird shadows. This is because the lens will
block part of the flash and you will get a weird shadow at the bottom
of your picture (it's the lens blocking the flash!). For bigger
(physically) lenses, you have
to use an external flash.
A picture of my cat, Duffy, using the built in flash and a lens that
was too big (my 10-22mm). See the horrible shadow?!
Flash Guide Number (GN):
The amount of light that a flash can deliver. Technically,
it's f/stop x distance to subject (usually at ISO 100). To use a
flash in manual mode, f/stop = GN divided by the number of feet
to the subject. For Canon flashes, the GN is the model
number divided by 10 (yes, crazy). So a 550EX has a GN of
55. However, this is sort of misleading because the 550EX is a
zoom flash (it has a lens in it) and the GN is calculated at it's
maximum zoom (which gives the best GN number (by the way, for the 550
the GN is calculated at zoom of 105mm)). A neat thing about
"smart" (E-TTL, Electronic - Thru The Lens) flashes like the
550EX is that it has variable flash power output. What this means
(in theory) is that I can put my camera in manual mode (or aperture
priority or speed priority) and the flash will calculate the correct
amount of flash/light (by using a pre-flash and metering the light thru
the lens). E-TTL usually works pretty good, and if it doesn't,
you can adjust your exposure by using exposure compensation (EV) or FEC
(Flash Exposure Compensation) or other tricks.
Lenses
Canon's best lenses are called "L" (Luxury) lenses. They are the
PRO quality lenses and cost alot, I don't have any of them. You
can tell if a Canon lenses is a "L" because it's name will have a "L"
in it (i.e. EF 17-40 mm f/4L). "L" lenses are also usually white
or have a red ring painted on them in the case of a black lens (like
the 17-40)(the white lens is a 70-200mm).
The really weird thing about lenses is the fact that their size doesn't
really tell you what their focal length is. Here is my 50mm and
10-22mm (the 10-22mm is much bigger):
The scale for the 50mm, 10-22mm, and 17-40mm is (closely) correct (the
white 70-200 is a smaller size/scale). Strangely, I think that my
10-22mm might be alittle bigger than the 17-40mm (physically).
And alot bigger than my 50mm.
Fast lens: A "fast" lens is one
that lets in alot of light, which means that you can use a faster
shutter for the same amount of light verses a "slow" lens (or, still
get a picture without a flash in low light). Fast lenses are
anything less than f/3, slow lenses are anything over f/5. My
Canon 50mm/f1.8 is a "fast" lens, my 75-300 f/4-5.6 is alittle "slow"
(but not bad). I've seen some telephoto lenses that where f/8 or
f/11 (that's really slow! You had better be in full
sun light to use it!) Of course, fast lenses are more expensive
than slow lenses (sometimes as much as 3X more expensive, compare the
Canon 50mm/f1.4 to the Canon 50mm/f1.8! ($294 vs $80 as of 1/22/05)).
Why isn't there a 10-300mm lens?
I don't know, I'm not an optical engineer, but I would guess that it's
just not a good idea. It could probably be done, but the picture
quality would be horrible. Once again, a tool made for a specific
purpose is always better than a general purpose tool (also relates to
the prime vs zoom lens argument). In general terms, the
focal length steps seem to be (plus or minus 10%) 10-30mm,
30-70mm, 70-300mm, and 300mm or greater.
Note: For those people with a
P&S camera or video camera with 300X zoom, it's a electronic zoom
(really cropping) and the quality at 300X zoom is almost ZERO! I
know, I have a Sony TVR-340 camcorder with 300X zoom, it sucks at 300X
zoom (I've locked out electronic zoom on my TVR-340). Never go
past the OPTICAL zoom on any camera! (You can always "zoom" in on
your pictures or video using a computer later using software, the
quality will be the same (or maybe better)).
To be continued...
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