If you use one of the consumer cameras, from the EOS 50D down, you may well have come across the A-DEP mode. But what does it do and how does it work?

 A-DEP stands for Auto Depth [of field] and it aims to give you enough depth of field in your image for the subjects you want to capture. It's most used for landscapes as this is where you most commonly want lots of depth of field. 

In A-DEP mode, the camera evaluates the scene and uses the focus points to determine the nearest and farthest subjects. One thing you need to be aware of is that it only picks up subjects under the focusing points - it won't find a subject not covered by them.

By calculating the distance from the nearest to farthest points, the camera can calculate a point to focus on and an aperture to use to give you enough depth of field to ensure they are all in focus. With this done it works out a shutter speed to use to give the correct exposure and you're ready to shoot. 

It's not a widley used mode really and for many, it is seen as a shortcut for those that don't yet understand the relationship between aperture, subject distance and depth of field, but if you're shooting a landscape it's worth experimenting with, even in conjunction with your normal method of shooting, just to see ther results. 

If asked the question above, what would you say the answer is? Is it:
a) A lens with a focal length greater than 200mm?
b) A lens which can change it's focal length?
c) A lens whose physical length is less than the focal length?

I expect most of you will go for answer "A" but you'd be wrong. In real terms, anything with a focal length over 200mm is termed a telephoto lens in common parlance...but, there is a clue in the fact that you often find lenses shorter than 200mm refered to as telelphotos. So what are they talking about? Well, the answer lies in techie talk. According to the Canon Lens Work book, a telephoto lens is defined as follows:
With general photographic lenses, the overall length of a lens (the distance from the apex of the front lens element to the focal plane) is longer than its focal length. This is not usually the case with lenses of particularly long focal length, however, since using a normal lens construction would result in a very large unwieldy lens. To keep the size of such a lens manageable while still providing a long focal length, a concave (negative) lens assembly is placed behind the main convex (positive) lens which is shorter than its focal length. Lenses of this type are called telephoto lenses. In a telephoto lens, the second principal point is located in front of the frontmost lens element.

Translated into simple terms, a telephoto lens is one that has a physical length (from the front lens element to the the focal plane) which is less than its stated focal length.

So, the new firmware for the EOS 5D Mark II will be arriving on the 2nd of June so we're told. What does it mean, and is it really a big step forwards for most users? To decide that, we need to look at what it's actually doing and why those features were not in the camera from the start.

The EOS 5D Mark II was the first EOS model to feature movie recording and the first camera from anyone to feature full HD recording. The market for this camera is huge. Possibly bigger than had been anticipated. It's also a very immature market in that there are no established users who have fixed ideas about what they're doing with the camera. The problem has come because the camera is simply so good at movie recording. If it had been a bit weak or not very good quality, the professional video guys would not have been interested and the standard full auto video mode would have been perfectly good enough for the people who were going to make use of the feature - those that have little or no experience with video and just want it to work without too much fuss.

That's the only reason I can see why Canon would have chosen to not give full manual control. If you think about it, giving the full control to a complete beginner with no experience is quite likely to lead to a bad user experience - it'll be too complex and the results won't be as good and they then won't use the feature.

Instead what's happened is that the camera was limited and the pro video guys got hold of it and wanted more - more control to get better results because they know what they're doing. They know what shutter speed and aperture will do to the results and how to use them creatively. I can already see there will be problems with the new firmware - beginner users will be confused and will end up shooting at (for example) faster shutter speeds than they need because they think they have to and it's what they're used to doing with still images of moving subjects. The reality is Canon could have simply given a few shutter speed choices - 1/30sec, 1/60sec, and then a break until the much higher speeds for specific results. 

And what about sound? Ask any video guy and they'll tell you that sound is more important than pictures. The image can be great, but if the sound is rubbish, the whole thing will be poor. That's another reason for the simple video controls - it was a set and forget feature. You can start recording and let it get on with it without having to touch the camera and risk getting 'handling sounds' from the camera body. Granted the internal microphone is not great and for good sound you should be using an external unit, but for you complete beginners in video it does the job and allows you to get video with sound of little Johnny running around the park. Now you'll almost certainly  have to buy an external microphone to get half decent sound because there will be more camera handling sounds going on as you adjust the aperture or ISO to get the right exposure. Suddenly the camera has gone from a product suitable for use by the masses to a one that is now capable of being used by everyone - amateur movie makers and pros alike but for almost everyone will require an external microphone.

So what am I complaining about? Well, it's this: If you've got full manual control and everyone is telling you it's a great thing, you'll be tempted to use it. If you don't know much about video, don't! By all means practice with it and find out how it works, but don't start shooting in manual movie mode and expect great results or you're setting yourself up for a fall.  

For the pros reading this - you're happy you've got full manual control, but don't think it's all about you. In fact, you're not the biggest market for cameras. Think how many consumers buy cameras when compared to how many pros. And that's why Canon did what they did. They're probably over the moon you're so pleased with their camera that you want to use it to film this, that and the other, but it was a first step into an uncertain market. So before you start complaining about the other things you want - Manual Audio Control and varying frame rates, stop and think. For pro users they'd be great, but for consumers it's another layer of complexity they need understand to get good results.