newbie depth of field question

[commando]

Gidday, i'm new to the forum, it looks like a nice place :) Hopefully i've posted this in the correct place...

I'm new to SLR photography, and i'm taking a class at the moment to help me get the basics right.

To practice, I thought i'd try and take a picture of my digital piano, from one end, with the end closest to me being in sharp focus, and the far end being out of focus. As I understand it, I need to use a large aperture and a reasonably quick shutter speed.

I wound my camera (EOS 300D with the kit lens, on a tripod) to it's maximum value (dial all the way to the left) while in Av mode, and took my photo. It turned out ok, but not as blurred at the far end as I was wanting. I don't have the photo with me right now, otherwise i'd post it. I tried both with the camera close to the piano, and further away with a bit of zoom. Can anyone suggest why it's not worked as well as i'd like?

I've seen a photo my tutor did (he's a pro), he managed to get such a narrow depth of field the front part of the ring was in focus and the back wasn't. I've no idea how he managed that.

[robertwgross]

Gidday, i'm new to the forum, it looks like a nice place :) Hopefully i've posted this in the correct place...

I'm new to SLR photography, and i'm taking a class at the moment to help me get the basics right.

To practice, I thought i'd try and take a picture of my digital piano, from one end, with the end closest to me being in sharp focus, and the far end being out of focus. As I understand it, I need to use a large aperture and a reasonably quick shutter speed.

I wound my camera (EOS 300D with the kit lens, on a tripod) to it's maximum value (dial all the way to the left) while in Av mode, and took my photo. It turned out ok, but not as blurred at the far end as I was wanting. I don't have the photo with me right now, otherwise i'd post it. I tried both with the camera close to the piano, and further away with a bit of zoom. Can anyone suggest why it's not worked as well as i'd like?

I've seen a photo my tutor did (he's a pro), he managed to get such a narrow depth of field the front part of the ring was in focus and the back wasn't. I've no idea how he managed that.

Well, the kit lens is not the very fastest lens in the world. By that, I mean that its maximum aperture is not super wide open. Something simple like the 50mm f/1.8 lens has a very nice maximum aperture. You may have dialed in the best that the equipment offered, but that may not be the very best result. At least you are thinking correctly, and you are headed in the right direction.

---Bob Gross---

[commando]

Thanks for that Bob, it's good to know that my understanding isn't at fault :) So the 50mm f/1.8 is good for that sort of work? It seems a bit much to me to buy a lens just to take one type of photo... what other kinds of photos would that lens be good for, or what advantages would it have over the kit lens? I have to guess it has a "magnification" factor about in the middle of the kit lens range. At least that lens isn't too expensive.

I'm also considering the 80-200mm lens, which is something like 128mm - 320mm equilivent. Is that a good lens for a beginner to buy, given that I want some kind of a "telephoto" lens? It's only F4.5/5.6, which seems to be a narrow aperature.

[robertwgross]

The 50mm f/1.8 lens is not very flexible in that it is a fixed focal length lens, but it is relatively fast (f/1.8) and very inexpensive. There are a very few lenses of f/1.4 or f/1.2, but they get expensive in a hurry. The simple 50mm f/1.8 is cheap enough that some photographers keep it around, purely for the low-light shot, or purely for that tight depth of field shot.

There are many telephoto lenses to choose from, too many to discuss here. How good of an aperture you need, and what kind of focal length you need, and how much you are willing to pay... The correct answer depends on the subject matter you are after.

I think that when I was a beginner and dinking around, that kind of telephoto lens appealed to me on price. The other one is 75-300mm. For a beginner, you see those all the time. However, if you ever get serious about your telephoto shots, you will be yearning to move up to a more serious lens. But then, that requires a more serious budget. There is no easy answer.

---Bob Gross---

[commando]

Since i'm still very new to this, I don't want to go crazy and buy a lens worth US$2000, or anything near that price range. All I really want is to be able to take pictures of things that are further away than my current lens will do! So long as it's better than what my old Canon A70 will do, i'll be happy for now :)

I can get the EF 90-300MM F/4.5-5.6 USM for around US$260, the CANON EF 55-200 F4.5-5.6 USM II for around US$349, or the CANON EF 80-200MM F/4.5-5.6 II for US$186. Any of them are in my price range, but the only way I can compare them is by their power and their aperture relative to each other. I don't know for example what I could get with an f2.0 lens that I couldn't get with a f4.0 lens.

So with the 50mm/1.8 lens do you think it'd be possible to get the sort of shot I described earlier, of the front of a wedding ring being in focus, while the back is fuzzy? That's a very narrow depth of field. Would it also be possible to get the piano shot with the same lens?

Thanks for your help, it's a steep enough learning curve for someone new, even if I am an engineer :)

[robertwgross]

So with the 50mm/1.8 lens do you think it'd be possible to get the sort of shot I described earlier, of the front of a wedding ring being in focus, while the back is fuzzy? That's a very narrow depth of field. Would it also be possible to get the piano shot with the same lens?


I don't know what wedding ring you refer to.

If you refer to closeup photography, then that is another thing. I use an extension tube on a normal zoom lens to make it into a quasi-macro lens for flowers and bugs. The depth of field tends to be rather narrow, and the focus process gets a little squirrelly. <that's a technical term>

---Bob Gross---

[commando]

Sorry, I was just referring to a picture I saw, a shot of a ring lying on a sheet. The front of the ring was in perfect focus, whereas the back of the ring (1cm further back) is nicely blurred. Could I (or someone who knows what they're doing) achieve this effect with the 50mm/1.8 lens? Or would I need an "extension tube" to achieve it?

Any thoughts on which of those cheaper lenses I mentioned earlier would be a good general purpose telephoto zoom lens for a beginner? Or should I just do a search? ;)

[billsh]

Commando,
DOF is an important concept to learn, and seems like you have the basics down pat. For specific information you might want to try one of the online calculators like this http://www.dofmaster.com/dofjs.html

You can also buy or create DOF charts which are helpful in the field.

[commando]

Thanks bill, that calculator's handy for seeing how changing one variable (focal length/aperature/distance) affects your depth of field.