This 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.

For questions about the DCRP site, please visit the About DCRP page.

Ok 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.

When shopping for a digital camera, I noticed large price discrepancies between various online shops. Why is this?

You 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:

• They call you and try to hard sell you accessories like filters, batteries, and carrying cases
• They try to charge you extra for things that should have been in the box, like the software and cables
• They 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

At this point, if you refuse to buy it, they will either hang up on you, or tell you that the camera is out of stock.

This 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!

What is an autofocus illuminator, and why do I want one?

Digital 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.

When 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 real problem.

That's 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 the end.

What 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 focus.

Cameras 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 idea.

What is this diopter correction knob that you keep talking about?

Diopter correction is a feature that allows you to focus the image in the optical viewfinder.

The 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.

What is the deal with the different "quality" settings on my camera?

Most, 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?

The 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

As 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.

I 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 card.

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 than on the film camera:

What an 18mm lens looks like on a D-SLR (such as the Digital Rebel)

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). That 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 conversion.

The conversion factor varies, from 1.5X to 2.0X on most D-SLRs.

Will a high resolution camera make better prints than a lower resolution camera?

To 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!

What does a wide-angle lens do?

Wide-angle 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

Do you know of a way to hook a digital camera up with a microscope or telescope?

Check out EagleEye and LensAdapter for products that may fit the bill.

I'm having trouble downloading photos to my computer with the software that came with my camera. What can I do?

Four 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.

What's the difference between optical zoom and digital zoom?

It's 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 effect.

Digital 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.

The 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, one fake.

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 in noise.

Why do all my indoor photos come out blurry?

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 400 film.

So what's the solution? Here are a few suggestions:

• 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, though)

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!

What kind of camera do I need to print out 4 x 6 inch images? What about 8 x 10's?

Here's a simple way of answering this question:

A 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.

What is interpolation and does it effect the quality of my photos?

Here's a nice explanation from Justin Karneges:

Interpolation 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.

The 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.

Now, 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:

1) 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.

You 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.

What 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!

So 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.

So 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.

Should I be have any concerns about putting my digital camera through the X-Ray machines at the airport?

Nope, there is no evidence that putting your camera through those machines causes any harm.