Silly question

Sorry if this seems a silly or pointless question. I still haven't bought my SLR yet. I had been thinking about the canon 450d. Im just trying to read as much before I finally buy as i've never used an SLR before so want to be aware. There are a few things confusing me.

When reading about the auto focus, it says it has nine points I understand that this means there are nine points that focus on whats near to it. I've read a few places people saying shoot on centre point, why is this?

Also i've seen some pictures taken on the 400d, 450d (not on this site) and other brands of camera where for example there are 3 subjects ie dogs in the picture with some background but the dogs are out of focus... is this the wrong setting, camera or lens? Ive never had this problem with my p+s everything is mostly always in focus, not too sure what kind of focussing it has all I know is in live view there is a little rectangle in middle.

I had a shot of a nikon SLR and the same thing happened, when its close up head shots they were in focus ok but a shot of my dog standing in the middle of the image was a bit soft and out of focus.. I know it was probably my fauly just wondering what causes this in so many images I see as I always like everything in the image to be nice and sharp.

Thanks

Well, that is called "depth of field". What that means is how much of the picture you want to be in focus. On an SLR you can set that. they are called "f-stops". It is all up to the photographer as to how much he wants in focus in the image. However, depending on the lens, it will change the amount that is able to be in focus.

Before you buy a SLR, do a little more reading, because there is no point in buying an SLR if you will just shoot in auto. The options are great and your creative side can really shine with an SLR, but you then need to know how it works.

Most use a single AF point so that there is no uncertainty about exactly what you are telling the camera to focus on.

The effect you are seeing is due to what is called "depth of field" or DoF. Only objects within a certain range of distances will appear in acceptable focus. The extent of that range depends on the distance at which the camera is focussed, the aperture setting of the lens, the sensor size, and the focal length of the lens. It is less noticeable on P+S cameras because they usually have "slow" lenses with narrow apertures, giving a large depth of field.

SarahB,
The center AF point is usually the most sensitive and will usually give best results, however the others also work well.

Having part of the subject not in focus is because of Depth of Field
A smaller aperture ex. f/16 will have more in focus then a larger aperture ex. f/5.6

Good luck with your future DSLR
Oh here is a good link by Canon that helps explain there DSLR's
Enjoy DSLR <-- click to see

HI Sarah,
I'll make it easy for you

Buy a used or new 40D or 50D. It will give you pleanty of room to grow, both a excellent value for money and you won't be 'wanting more' anytime soon.

The 450D, whilst a very good camera is very light and small in the hands.

Autofocus, etc are only a small part of the camera and on the Canon amatuer / semi pro bodies are pretty much the same.

SarahB wrote in post #9377260
Sorry if this seems a silly or pointless question. I still haven't bought my SLR yet. I had been thinking about the canon 450d. Im just trying to read as much before I finally buy as i've never used an SLR before so want to be aware. There are a few things confusing me.

When reading about the auto focus, it says it has nine points I understand that this means there are nine points that focus on whats near to it. I've read a few places people saying shoot on centre point, why is this?

Also i've seen some pictures taken on the 400d, 450d (not on this site) and other brands of camera where for example there are 3 subjects ie dogs in the picture with some background but the dogs are out of focus... is this the wrong setting, camera or lens? Ive never had this problem with my p+s everything is mostly always in focus, not too sure what kind of focussing it has all I know is in live view there is a little rectangle in middle.

I had a shot of a nikon SLR and the same thing happened, when its close up head shots they were in focus ok but a shot of my dog standing in the middle of the image was a bit soft and out of focus.. I know it was probably my fauly just wondering what causes this in so many images I see as I always like everything in the image to be nice and sharp.

Thanks

You really need to read up on depth of field and the relationship between the aperture setting and the depth of focus that you get in your image.

I relay suggest that you do some internet research on "Depth of Field" as there are many good papers and sites giving you the detail you need. Then if there is any specific points you do not understand ask here.

Thanks for the replies. I have been reading lots about the apeture etc.. and understand a lot more than I did a few weeks ago. I think I just got confused as when I was in a shop a canon rep was talking to me and he said you can't get background and foreground both in focus unless you use a really small apeture and a tripod. which confused me as i've seen others pictures where both are in focus without tripod and then others where the subject is blurred, so i guess its all about getting used to everything and understand how everything is linked together. I have printed some information off and have bought a magazine also as I want to fully understand this so not to be disappointed as I do like to take a lot of pictures with my dog with the scenery in the background

What confuses many P&S users about depth of field is the fact that most Point and Shoot cameras have very small sensors and thus very short focal length lenses which gives very wide depth of field and as you say, the dog and the forest in the background will both be in focus. You can do this with a DSLR too if you want but most people like their subject isolated from a nice background so the dog will stand out. You can do it both ways with a DSLR while isolating the subject is difficult or impossible with many low end P&S cameras.

Thanks for that hpulley. You are right, with my p+s if im taking a non close up of my dog with a background, the background is never blurred, I must be the opposite of most as thats the way I like it as I like to take my dog different places and capture her with different backgrounds. With my p+s close up pictures can have blurred backgrounds or macro. What I look forward to with the dslr is experimenting and trying new techniques and seeing different types of pictures. As long as I know it is possible to achieve hand held results with both in focus I am happy

SarahB wrote in post #9377332
* * *a canon rep was talking to me and he said you can't get background and foreground both in focus unless you use a really small apeture and a tripod. * * *

He probably meant that to get the sharpest possible focus you will need a tripod, and to get the maximum depth of acceptable focus (depth of field) you'll need a small aperture (large f-stop), which means the camera will need a very slow shutter speed to get enough light, which translates into probably needing a tripod to keep the camera steady because of the slow shutter speed. As you said, you can take a handheld shot with a small aperture and get just about everything in focus, but this will work best in bright light so you don't need as slow a shutter speed to balance the small aperture.

When you are shooting at a small aperture like f/11, chances are good that you will get most of the frame in focus. That being said, you would most likely need a tripod or flash to shoot f/11 indoors. In my house, an f/11 shot meters are 1/30th of a second exposure at ISO 3200. If I were outdoors during a sunny day, I can shoot at f/11 handheld no problem

another vote for a clean, used 40D. The AF is much better than on the old rebel XT. I think the XTi and the XSi have the cross point AF in the center but the XS does not. I would even see about a clean used 30D for like $450? Pair it with a good used starter lens (18-55IS, make sure it's the IS) or the tamron 17-50 for a little more money and you are in business. The tamron is an f/2.8 which I think you'll like MUCH more once you get the hang of depth of field.

I think you're doing it the right way....Research research research....Take a very hard look at the Nikon offerings too....You might just end up getting hooked on Photography (like the rest of us) and if you do, you'll likely find that the body you buy is secondary to the lenses and accesories you purchase (ie. Flash, tripod)

Thanks, I think at this rate I'll never get a camera lol as its all too confusing. The 40d does seem to keep coming up and I am tempted, I can buy refurbished from canon for about £400-£500 but still don't know. Im still looking at the nikon d5000 can't afford the d90 and I think the d5000 is the best out of their range I can afford.

I just want my first dslr to have excellent image quality for taking the type of picture I do and also have the scope to experiment. I do like lovely sharp a well coloured photos. Also a camera that produces straight out of the camera good quality jpegs for starting out as I know nothing about raw and pp and good auto settings for starting out so I don't miss out on anything palying with the settings.

Everyone is going to recommend the 40D because it is a better camera, BUT is it the right camera for you.

My wife really enjoys shooting but is always complaining about the weight of the camera. When you add more expensive lenses like the 17-55 and maybe a flash... yikes! it's really heavy.

The rebels are nice cameras. Lighter and smaller which might actually fit your hands better.

You will really need to go to the camera store and try out both cameras for feel and weight. Also consider which lens you are going to use. Most likely just the Kit lens... but still don't let feature creep bias your decision. If it's too heavy or uncomfortable for you, you won't shoot and then you have an awesome camera that you can grow into that you'll never use.