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Introduction Season's greetings from the Digital SLR Guide! I hope that this newsletter finds you and you warm, well, and enjoying some time off. Even though the chilly weather makes it a bit harder to keep my fingers warm as I type, I have been hard at work adding new content to the Digital SLR Guide to help you find the best digital SLR camera, and provide you with more information about the one you already own. A couple of months ago I asked for readers of this newsletter to provide me with their constructive feedback about what they liked and what additional information they would like to me cover. A common question from many of the people who responded was "how do I find the right lens?" It's a good question. While there are only a handful of digital SLR cameras on the market, there are hundreds of lenses - holdovers from all the film SLR cameras that have come before. It's also a worthwhile question because lenses come in all shapes and sizes and each one is going to meet the needs of a specific photography style: for example, a bird enthusiast and a landscape photographer should not both invest in the exact same lens. With all this in mind, I've put together a little something that I think will help you out: it's the Digital SLR Lens Guide. The lens guide is a 6-step process (much like the 4-step process that I recommend for finding the best digital SLR) and it's the same 6 steps that I use every time I go out looking for a new camera lens. Key to these steps is a free PDF for you to download: your digital SLR lens wishlist. Without going into great detail here, let me say this about it: a digital SLR lens wishlist is a checklist that identifies your "ideal" lens. Once you complete the wishlist, all you have to do is go out and find the couple of lenses that closely match your wishlist lens. It's a much simpler way of quickly narrowing down the field of available options, and focusing on just those lenses that will help you take the photos that you love.

In This Issue A shiny new lens guide What are f-stops? Photojojo.com When to Turn Off Anti-Shake The Fuji S5Pro The Canon Rebel xTi Adobe Elements Latest SLR Guides Sony ALPHA A100 Nikon D70s Digital SLR Terms Megapixels Anti-Shake ISO / Image Noise Sensor Dust Crop Factor RAW vs. JPG Continuous Photos Aspect Ratio Recent Updates Find a Lens - Intro Focal Length Prime vs. Zoom Maximum Aperture First and Third Party Lenses SLR Lens Features How to Pick a Lens SLR Lens Wishlist Small Sized Digital SLR Cameras Digital SLR Tips When to Change ISO The Best Digital Photography Books

Digital SLR Q & A

Question: What are f-stops?

Answer

In last month's newsletter I talked about aperture and noted that by changing the aperture you can alter the amount of light that passes through the lens and enters the camera.

I also mentioned that the aperture numbers that appear on your digital SLR camera are the inverse of what you'd expect: a small number like 3.5 is a wide aperture and a large number like 16 is a narrow aperture.

In this month's Q & A, I'm going to dig a bit deeper into what these numbers really mean.

To answer the question above directly, an f-stop is simply a unit of measurement like a mile, meter, gram or ounce. Since the f-stop is the unit of measurement for aperture settings, this explains why all aperture references are preceded by an f (f/2.8, f/8, f/16).

Aperture numbers aren't all over the map and aren't just any number you can think up in your head (there is no f/4.9). Instead, there's a common set of aperture numbers that are used by digital SLR lenses:

1.4

2.0

2.8

4.0

5.6

8.0

11

16

22

32

Important point #1: as the aperture number increases to the next value in the scale, half the amount of light enters the camera.

Changing from an aperture of f/2.8 to f/4.0 (1 full f-stop) HALVES the amount of light passing through the lens and into the camera. Conversely, switching from f/4.0 to f/2.8 DOUBLES the amount of light passing through the lens.

Important point #2: you don't always have to make aperture changes in full stops.

Think of the aperture values that I presented in the table above like measurements on a ruler. Whether you measure things in inches or millimeters, the same reasoning applies: in between each one of the primary numbers on the ruler, there are finer measurements that you can make. You can wind up with a measurement of 3.25 inches or 5.5 millimeters.

The same sort of fractional measurements can be used with f-stops, and there are two different ways that digital SLR cameras handle this: some are able to change aperture in half-stops, while others are set to make changes in third-stops.

The following table shows you an aperture f-stop scale with half-stops (the whole stops appear in bold):

2.8

3.5

4.0

4.5

5.6

6.7

8.0

9.5

11

13

16

19

And this table shows you aperture f-stops in third-stops (again, whole stops appear in bold):

2.8

3.2

3.5

4.0

4.5

5.0

5.6

6.3

7.1

8.0

9.0

10

11

So there you have it - f-stops are a unit of measurement that can be measured in whole, half and thirds increments. Understanding this scale becomes especially important when you switch your SLR out of AUTO mode and start using more manual controls.

But we'll get into that next month.

Learning Resource

A wealth of interesting photography ideas and projects awaits you at Photojojo.com, a web site and newsletter whose self-described motto is "We find the best photo shiz anywhere".

This irreverent attitude permeates the content of the site, where you'll find such interesting (and odd) photo tidbits as these:

• Do-it-yourself holiday photo gifts
• How to create ornaments out of your favorite digital photos
• The Gorillapod SLR Zoom - an innovative alternative to the standard tripod
• How to give an aquarium a photo makeover

It's almost impossible to verbally describe the WIDE variety of information that pops up on this site, so I'll just give you the link here and let you go have a look for yourself: Photojojo.com

How and When

This month's How and When section is going to delve into something that's a bit counter-intuitive...

When to Turn Off Anti-Shake

I can already hear the cries of protest.

Why in the world would you spend money on an advanced digital SLR camera that includes built-in anti-shake, and then go and turn it off?

There's a perfectly good reason for doing so, and here's the key: it all depends on how fast your SUBJECT is moving.

I think anti-shake is a fantastic tool for the average snapshot photographer, and that's why it's no surprise that many more SLR and compact digital cameras are including this helpful technology.

The big deal here is that anti-shake reduces camera vibration when you hold your SLR in your hands, which in turn leads to clearer photos. That's the simple definition.

The more complex one is that anti-shake helps you take clear photos when your camera selects a slow shutter speed to get a correct exposure. The slower the shutter speed your camera uses, the higher your chance of getting a blurry photo due to camera shake.

Let's put this into table form to illustrate your changes of getting a blurry photo at different shutter speeds:

Shutter Speed	Without Anti-shake	With Anti-shake
1/500th of a second	zero	zero
1/250th of a second	low	zero
1/125th of a second	moderate	low
1/60th of a second	high	moderate
1/10th of a second	very high	high

See what's happening here? Anti-shake just reduces the probability of blurry photos, since you can use very slow shutter speeds and still get clear images (without anti-shake those same slow shutter speeds result in blur).

Key point: anti-shake only applies when you're not using the flash.

The minute you activate your camera's flash, anti-shake's ability to counteract slow shutter speed no longer applies. The reason is that the camera wants to activate the flash when it senses that there isn't enough light. As soon as the flash is active, the camera will set a shutter speed (typically around 1/60th of a second) so that you won't get a blurry photo.

Your flash must be turned off in order for anti-shake to work its magic at shutter speeds slower than 1/60th of a second.

This is why anti-shake is an incredibly useful feature for anyone who takes photos indoors without a flash: specifically, the interior of houses, museums and aquariums. If you want to take some photos of your relatives standing in front of an ancient artifact, anti-shake will ensure that your photo turns out crisp and clear.

But if those same relatives are romping all over the museum, your trusty anti-shake isn't going to do a bit of good.

The problem here is that even though the anti-shake is working to reduce the camera's vibration, the only thing that will freeze the motion of a fast-moving subject is a fast shutter speed. Since the use of anti-shake doesn't necessarily increase your shutter speed, it won't help you get clear shots of fast-moving subjects.

Let's talk about some concrete examples that will help clarify what's going on here.

Scenario One

1. You're in the living room and find your child asleep on the floor - this is just too good to pass up
2. You take out your camera and prepare to take a photo - you disable the flash and notice that the camera wants to use a shutter speed of 1/30th of a second
3. RESULT: with anti-shake activated, this shot will turn out quite clear

Scenario Two

1. You're in the living room and find your child jumping from one couch to the other
2. You still don't want to use the flash and the camera selects a shutter speed of 1/30th of a second
3. RESULT: while the room will be quite clear (it's not moving around) your child will just be a blur. 1/30th of a second is NOT fast enough to freeze the motion of a jumping child (or any other moving subject for that matter).

In scenario number two anti-shake isn't going to help you get the clear photo that you're looking for - might as well turn it off. Instead, use two other techniques that WILL increase your shutter speed:

1. Open your lens up to its widest maximum aperture AND
2. Increase the ISO setting on your camera

Doing these two things (and not relying on your anti-shake system) will ensure that you get a clear photo in dim lighting (without the flash), even though your subject is moving all over the place.

Cameras and Accessories

In Conclusion

It's been a great year for the Digital SLR Guide, and I certainly hope that it's been a good one for you too.

Digital SLR development does not seem to be slowing down in any way, so it looks like I'll have a lot to chatter about for a long time to come.

Thanks for reading, Happy Holidays, best wishes for the New Year and most of all...happy picture-taking!

--Chris Roberts, Your Digital SLR Guide