is an attempt to answer the most frequently asked
questions that arrive in my mailbox. It will also
help you in picking out the right digital camera.
questions about the DCRP site, please visit the About
Jeff, be honest. I have $xxx to spend on a
digital camera. Which one should I get?
Please see the list of my favorite cameras on this page.
shopping for a digital camera, I noticed large
price discrepancies between various online shops.
Why is this?
know the old saying "if it's too good to be
true, then it probably is"? That's very important
to remember when shopping online for a digital camera.
Let's say you're browsing the price listings for
a Canon Rebel XSi, While most everyone else is selling
them for $799, you see one place selling it for $499.
You order them and here's what probably happens next:
call you and try to hard sell you accessories like
filters, batteries, and carrying cases
try to charge you extra for things that should
have been in the box, like the software and cables
will tell you that the camera you've bought is "gray
market", meaning not sold in the US, and not
covered under the manufacturer's warranty
this point, if you refuse to buy it, they will either
hang up on you, or tell you that the camera is out
may sound funny, but 9 times out of 10, these resellers
will be located in New York City. They lure you in
with a low price and then charge you $100 for shipping,
or $200 more for the US model. My advice: read ratings
of the merchants on PriceGrabber and Reseller
Ratings, before you get burned!
is an AF-assist lamp, and why do I want
cameras use something called "contrast detection" when
they focus on a subject. I'm not going to go into
the technical explanation of how it works since it
doesn't really help with this question.
light levels are low, the camera may not be able
to decide on a focus distance. Some cameras won't
take a picture, while others default to some preset
focus distance (usually infinity). This can be a
where AF illuminators -- also called AF assist lamps
-- come into play. They cast a bright, focused beam
of light -- usually white or orange -- onto the subject,
so the camera can "see" a little better
and focus properly. Other cameras use infrared or
laser-based focusing, but it's the same result in
is low light exactly? For me, that's indoors without
very strong lighting. There are some cameras that
I can't even do the redeye test on because they won't
with an AF illuminator do a much better job in these
situations, and that's probably why you'll want one.
If you do lots of outdoor or studio photography it's
not a big deal, but for indoor candids, it's a good
is this diopter correction knob that you keep
correction is a feature that allows you to focus
the image in the optical viewfinder.
diopter correction is manipulated by a knob, slider,
or dial located next to the viewfinder. Turning it
will focus the image. This is helpful in situations
where you remove your glasses to use the camera.
The image would be blurry without this useful feature.
It is usually only found on larger cameras.
is the deal with the different "quality" settings
on my camera?
if not all, cameras have several image quality settings
to choose from. They are first broken down by resolution
(e.g. 2048 x 1536, 1600 x 1200, 1024 x 768, etc)
and then by quality (e.g. SHQ, HQ, SQ). What's the
right one to use?
deal is this: quality is inversely proportional to
the amount of JPEG compression the camera uses. Thus,
a higher quality image will have less compression,
and vice versa.
High quality, low compression
Low quality, high compression
you lower the quality and increased the compression,
there will be more "artifacts" in your
image. The artifacts are a result of the higher JPEG
compression. You will notice that edges will seem
blurry, or little squares will appear. See the example
above for a good illustration of this.
recommend using the middle setting for everyday shooting.
If you're making big prints, consider using the highest
quality JPEG level. I'd skip over TIFF mode, as the
quality really isn't any better than high quality
JPEG, but they take up much more space on your memory
What is the focal length conversion
ratio (or crop factor) on a digital SLR?
Unless it's a very expensive full-frame
model, all digital SLRs will have a focal length conversion
(also called a field-of-view crop factor) to deal with.
Basically you have to re-train your mind to think in
digital SLR, rather than 35mm terms.
Let's imagine this scenario. You grab
your old Canon Rebel film camera and take a picture
with an 18mm lens. The picture comes out like so:
What an 18mm lens looks like on a 35mm camera
Now move that same
lens over to the Digital Rebel. Due to the difference
in size between the CMOS sensor in the Digital Rebel
and 35mm film (that the film Rebel uses), the digital
camera captures a smaller area using that same lens
What an 18mm lens looks like on a D-SLR (such as the
Thus, the image is
cropped in the center of the frame. The 18mm lens on
the Digital Rebel has the same field-of-view as
a 28.8 mm lens on the film Rebel (1.6X conversion ratio).
means that a lens that was wide-angle on your film
camera isn't nearly as wide on your D-SLR. Thankfully,
wider lenses are becoming available. If you're a telephoto
lover then you can see the benefits of the focal length
The conversion factor varies, from
1.5X to 2.0X on most D-SLRs.
a high resolution camera make better prints
than a lower resolution camera?
be more specific: will you get better 4 x 6 inch
prints from a 3 or 4 Megapixel camera versus a 2
Megapixel camera? Possibly, but the average person
won't notice. The real advantage of a higher resolution
camera is that with the larger image size, there's
more room to crop images. In terms of quality though,
it's not a huge deal. At print sizes like 8 x 10
inch, you will notice a difference.
What's the difference between USB
2.0 Full Speed and USB 2.0 High Speed?
Lots of cameras claim to have USB
2.0, but read the specs carefully before you get too
excited! There are two types of USB 2.0: Full Speed
and High Speed. USB 2.0 Full Speed tops out at 12 Mbit/sec,
which is the same speed as the "old" USB 1.1 standard.
In other words, this is marketing (bordering on deceptive)
and nothing more.
What you really want is USB 2.0 High
Speed. This protocol has a transfer rate of 480 Mbit/sec,
which is 40 times faster than USB 2.0 Full Speed. And
that makes a huge difference when you're transferring
2-4 Megabyte images to your computer!
does a wide-angle lens do?
lenses give you a view "further back" in
the frame than your typical 35mm lens. They're especially
useful indoors, where you can capture more of a room
in your photo. A lens is considered wide-angle when
it's 30mm or below. Here's an example:
28mm wide-angle lens
Typical 36mm lens
you know of a way to hook a digital camera
up with a microscope or telescope?
out EagleEye and LensAdapter for
products that may fit the bill.
having trouble downloading photos to my computer
with the software that came with my camera.
What can I do?
words: buy a card reader. Then, when you insert the
memory card, it will mount to your desktop just like
another disc, and you can copy the photos directly
to your hard disk. You can then use your favorite
photo editing software to retouch your photos.
the difference between optical zoom and digital
important to understand this difference, as you could
end up mighty disappointed with the results if you
get one rather than the other. Optical zoom is similar
to what you'll find in a regular 35mm camera: When
you push the button to zoom in or out, physical lens
elements move inside the camera, to achieve the desired
zoom, on the other hand, has no moving parts. Using
the "electronic brain" within the camera
instead, the camera takes a look at what it's "looking
at", and digitally zooms in, usually two or
three times closer.
problem with digital zoom is that you lose quality
when you do this -- your images will tend to be more "pixelated" than
the same image taken with an optical zoom camera.
This is due to the "interpolation" the
camera uses, which is a nice way of saying that it
makes a guess about how the picture should look while
zoomed in. Having optical AND digital zoom on a camera
isn't bad, but I'd try to avoid cameras with only
digital zoom, myself.
What's the difference between optical
and electronic image stabilization?
Lately, some camera manufacturers
have been misleading consumers, claiming that a camera
supports image stabilization, when it really does not.
There are two types of image stabilization: one real,
Optical image stabilization is the
one you want. While the basic concept is the same,
there are two different types of optical stabilization:
lens shift, and CCD shift. In both cases the camera
has gyroscopic sensors that detect camera shake, which
is caused by the tiny movements of your hands. The
camera then either shifts a lens element, or the CCD
itself (which is mounted on a movable platform) to
compensate for this motion. Typically this gives you
a 2-4 stop advantage over unstabilized cameras.
There are two types of electronic
stabilization as well, though neither as effective
as an optical system. The first one (which has many
names, such as natural light mode, high sensitivity
mode, anti-blur mode, picture stabilization mode, etc)
boosts the ISO sensitivity until you get a shutter
speed fast enough for a sharp photo. The problem with
this concept is that high ISO = more noise.
The other type of electronic image
stabilization is when a camera applies some kind of
post-processing to a photo, trying to remove the blur.
Most often this is like using "unsharp mask" in Photoshop.
This too adds more noise to your photos.
So, you want an optical IS system,
since it gives you sharp photos without an increase
Why do all my indoor photos come out
This is a very common question and
nine out of ten times it's the same scenario: people
taking shots indoors without the flash. Just because
the camera is digital it doesn't mean that the laws
of physics don't apply! If the shutter speed you're
using is slower than 1/30 or 1/60 of a second, odds
are that the shot will be blurry! A lot of people migrating
from film cameras say "well my photos were always
sharp with my film camera in these situations",
and a likely explanation for that is the use of ISO
So what's the solution? Here are a
- Use the flash
- Add more light to the room, if possible
- Use a tripod
- Turn up the ISO sensitivity a notch or two. Note
that doing this will increase the amount of noise
in your image
- If you haven't bought a camera yet, consider one
with image stabilization (this is still a rare feature,
Should I buy a "high speed" or "pro" memory card?
In general these are a waste of money. The only times
you may need one of these is if the camera requires
one for a certain function (like a high performance
movie or burst modes) or if the camera takes advantage
of them (currently this applies only to digital SLRs).
Do more Megapixels translate into better photo quality?
No. Despite what the sales person at the electronics store may have told you, more pixels does NOT mean better photo quality. Increasing the Megapixels (resolution) of the camera merely increases the size of the photo. This means that you can make larger prints, or crop a large area without losing too much detail. Since even a 4 Megapixel camera can make a nice 8 x 10 inch print, there's no need to spend more money on an 8 or 10 Megapixel camera.
Believe it or not, high resolution cameras may even have worse photo quality than their lower resolution counterparts. The more pixels on a camera's sensor, the more tightly packed together they are. That means more noise, less sensitivity, and potentially more purple fringing.
So don't be fooled by the Megapixel myth!
kind of camera do I need to print out 4 x 6
inch images? What about 8 x 10's?
a simple way of answering this question:
|4 x 6 in.
|5 x 7 in.
|8 x 10 in.
4 Megapixel camera will not make better 4 x 6 inch
prints than a 2 Megapixel camera. However, it does
capture a lot more detail, allowing you to crop your
image while still maintaining enough resolution for
a high quality print.
Why is there a delay after I push the shutter release button before I can take another picture?
There are many reasons for this delay... here's a few... (thanks to the people who wrote in for this one..)
The camera must:
- Set the focus, exposure time, white balance, etc.
- Charge up the CCD (apparently it can't hold the charge for long, so it does it right before you shoot)
- Copy the image out of the CCD into RAM.
- Compress the image after it's been taken
- Write the image to the flash memory.
As we know, newer cameras are getting faster and faster!
Why do some of your night test photos show reflections in the water, while others don't? If I don't see reflections, does this mean that the camera is bad at night shots?
|Nights like this are rare
||This is more typical
No, not at all. Conditions on the San Francisco Bay vary night to night, and the reflections are actually a rare sight. If a camera captures these reflections, it's merely a coincidence, and not an indicator of the quality of the camera.
is interpolation and does it effect the quality
of my photos?
a nice explanation from Justin Karneges:
is a fancy word for a computer "guessing".
The only type of interpolation that anyone should
be worried about is when an image is enlarged.
Basically, when an image is enlarged, you end up
with more pixels. But where did these pixels come
from? Back in the old days, if you enlarged a 320x240
image to 640x480, the program would just double-up
each pixel. Thus, the image looked blocky. Nowadays,
with more advanced programs like Photoshop, interpolation
(some even using advanced calculus) can be done
on the photo while enlarging. The interpolation
calculations allow the computer to pick better
pixels to add to the image rather than just using
the pixel next to it. This way, when you enlarge
an image, the image looks a lot smoother and cleaner.
Note that the amount of photo information hasn't
changed. If you look at an enlarged interpolated
picture, you will see that if a person was a white
dot because they were too far away, then they will
still be a white dot only bigger. If you had an
optical zoom then they would have looked more of
like a person. But if you don't optical zoom, and
then instead interpolate to get a closer view,
it isn't going to change much.
moral of the story? Well, you can't substitute
a 320x240 camera for a Megapixel camera by using
Photoshop to enlarge all your stuff to 1280x960.
It just doesn't work like that. You still only
have 320x240 worth of photo information.
as for cameras with interpolation. From my point
of view, a camera doesn't need interpolation. If
the lens only brings in X amount of pixels, then
so be it. If I want it bigger, I'll use Photoshop.
There are three reasons I'd do it this way:
Photoshop probably has a better interpolation routine
considering it's a multi-megabyte program running
on a pentium (or mac or what have you).
2) By not having the camera interpolate to a larger size, the photo doesn't
take as much space as it would have, yet you still have the same amount of
digital information. Doesn't waste space.
3) Your camera will operate faster because it won't have to spend time interpolating
a large image.
can see my philosophy in the Olympus D-400 Zoom.
One of it's features is a 2X digital zoom. The
normal lens of the D-400 is 1280x960. When in 2X
zoom mode, it takes the center 640x480 section
of that 1280x960 image. Now, all digital zoom cameras
do that. But what's different about the Olympus
is in the next step. At this point, most digicams
(like the Coolpix 900) will interpolate the 640x480
cropped section up to 1280x960 to simulate a 2X
zoom (which is all digital zoom really is.. just
a simulation) and save it to the card.
the Olympus does though, is save that center-cut
640x480 section. This kinda makes it seem like
it didn't zoom at all. Like, all it really did
was take a 1280x960 image and crop it to 640x480.
Well, that's exactly right. It did!
what's different about the way the Olympus handles
this? It didn't have to take the time to interpolate
it and write a humongous image to the flash card!
The same amount of photo information was saved
to the card as the other cameras except that the
Olympus is writing a smaller file. I can then later
enlarge the 640x480 image to 1280x960 (if I really
want to) using Photoshop and I'll have the same
image as the Coolpix did in 2X digital zoom mode.
basically, interpolation is not that great. Your
image software will use it before printing to your
photo printer (since most of the time, your image
is not EXACTLY the size that you're printing) which
is fine. However having it in a camera really doesn't
help you at all unless you don't own adequate software
for resizing your images yourself.
I be have any concerns about putting my digital
camera through the X-Ray machines at the airport?
there is no evidence that putting your camera through
those machines causes any harm.