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[BugCatcher]

I'm trying to figure out how to get a very shallow DOF at medium range, but I can't seem to do it. Here are a couple examples of what I'm talking about:

I've played around with the aperture and manual focus of my camera, but I don't know why I can't replicate the effect. I can do macro shots with shallow DOF just fine, but the farther away I set the focus, the more the entire scene becomes clear.

These pictures were all taken at F2.8 (the largest aperture on my camera). The focus point was set to minimum distance, 10cm, 20cm, 50cm, 1m, and infinity, respectively. When I focus on something far away, I would expect the stuff in the foreground to become blurry, but it just doesn't happen. What am I doing wrong?

 

[mrklaw]

standard crappy digicam, or DSLR/SLR? digicams aren't good a shallow DOF. Macro helps because its an extreme case, but generally your 2.8 on a digicam is equivalent of an F4 or higher on a film camera.

There are things you can do to help. If you have a good zoom, use as much zoom as possible,which helps to create shallow DOF. But your camera might compensate with larger aperture, which doesn't help.

 

[nitewulf]

yeah standard fixed lens digital cameras just arent good for shallow depth of field effects, but DSLRS are fine, one of my main reasons for wanting one.
having said that, you can use th macro mode, and then focus manually on your subject and fool the camera. but be warned, its extremely tough to get a sharp focus.
another way, the way i do it to make decent portraits with my digital camera, go all manual, sit or stand 4/5 feet from the subject(s). zoom in so your subject(s) covers most of the frame. open up the aperture (bringing the F number down, sorry about the confusion) as much as you can and focus your subjects manually. never auto.
take your shot. take repeated shots and you should have some good ones. i could post some of mine if you're interested.
cheers.

 

[nitewulf]

These pictures were all taken at 2.8F (the largest aperture on my camera). The focus point was set to minimum distance, 10cm, 20cm, 50cm, 1m, and infinity, respectively. When I focus on something far away, I would expect the stuff in the foreground to become blurry, but it just doesn't happen. What am I doing wrong?

you camera's aperture just doesnt open up enough. the larger it is, the shallower the focus will be.

 

[mrkgoo]

I'm so mateur it's not funny, but lower F-- = greater apeture, right? (it's a reciprocal relationship or something?) So when you guys say for a shallower DOF lower the apeture, do you mean closing it for a larger F, or opening for lower F? Or do I have this all wrong?

 

[mrkgoo]

you camera's aperture just doesnt open up enough. the larger it is, the shallower the focus will be.

NM, I just read this. Thanks.

 

[Richard Cranium]

It's all physics, really. Besides sensor size, DOF depends on the aperture, focal length, and distance to subject. Basically, large sensors, long focal lengths, and being close to the subject will all contribute to shallow DOF. The reason why you get a really shallow DOF on macros is because you're so close to the subject. It's also the reason why focusing to infinity will give you a very large DOF regardless of your aperture size. You could try to get more DOF by increasing the focal length to maximum (zoom all the way in), but the small sensor most digital cameras use is going to give you a fairly large DOF regardless of the situation. DSLRs have relatively huge sensors compared to other digicams, so they have a much shallower DOF.

You can do a search for online DOF calculators to see how these factors work.

 

[BugCatcher]

Thanks for the help, everybody. mrklaw, to answer your question, I'm using a Canon PowerShot A80. The focal length of the camera ranges from 35mm to 105mm equivalent, but if I zoom in at all, the largest aperture available slowly closes down to F4.9, so I have to take them at 35mm to get F2.8.

What kind of f-stop do I need to achieve the shallow DOF in the picture at the top of the thread? F1.4? F1? I'd like a DSLR someday, but I can't afford one right now. I looked at a whole bunch on dpreview, but it doesn't seem like there are any sub-$1000 ones out there than can do better than F2.8.

Is there anything I can do in the meanwhile? Will adding a tele lens make a big difference, or is it pointless for a camera like mine? Do I have to buy a $1000+ DSLR (or film camera) to do what I want?

 

[nitewulf]

you can buy any fairly cheap film SLR, w/ a lens that'll enable lower f numbers at high zoom to achieve good shallow DoF effects.
at 2.8 you should be able to achieve nice effects as well, following my directions. dont stand too far from the subject, ie, so you dont have to zoom too much! and make sure the subject takes over 1/3 of the frame.

 

[mrklaw]

bugcatcher,

yeah, common trait of digicams. You zoom in to try and help with DOF, and the F-stop increases too.

There is usually a sweet spot somewhere around 1/3rd zoom where the aperture stays relatively open. Thats as good as you'll get.

I'm half tempted to get a cheap DSLR next after my current digicam. I'm enjoying portrait work and its a controlled environment so I should be OK with all the controls. I've previously been put off by film SLRs simply because there is so much to do - focus, aperture, shutter speed, light meters, flash etc. Digicams got me into photography, so hopefully DSLRs will hold my hand a little bit

 

[BugCatcher]

Thanks again for the advice and tips, guys. It's good to know what's causing the problem, even if I can't do much about it. For now, I think I'll just stick with what I've got and see how far I can push this camera for the next year or two. I've been spoiled by digital, so I'm not really keen on the idea of buying a film camera, even if they aren't expensive. After looking around a bit, I've got my eye on the Digital Rebel XT. It looks like it can do everything I want in a DSLR (except GPS), so now it's my dream camera I want something in the $600-800 range, and that's where the XT should be when I'm ready to upgrade again.

 

[Warm Machine]

A manual film SLR isn't very complicated. As long as it has a good exposure/light meter it is pretty simple. You just have to know a few things about the traits of lenses.

You will pretty well never get anything in the way of narrow DOF with a strictly wide angle lens such as a 28mm or lower (In film terms that is. The equivalent on a digital is a 15mm. In a way it is similar to km to miles in terms of conversion. An 80mm film lens is a 55mm digital for example).

Think about why this is for a moment. If the background is out of focus it is so far away and taking up so little space on the image that it is impossible to tell anyway. Things always look crisper when they are smaller.

All that is important to shooting a decent picture is making sure the exposure meter is reading neutral and that the shutter speed is high enough that the whole shot isn't going to get blurred to hell.

How do you know that the shutter speed is high enough? There is a simple rule. Whatever mm lens you are zoomed in at you need aproximately the equivalent in shutter speed. So if you've got a monster 1000mm lens you have to be shooting at around 1000th of a second to capture a crisp image.

If you want a very narrow DOF you have to use a higher mm zoom and drop the f-stop down to a smaller number, preferably as small as you can depending on just how blown out you want the background. When you look through the lens of a film camera you are seeing the world at the smallest number the F-stop will go so that is a good guide to just how focused or out of focused you are going to get at the lowest setting.

Doing what you are doing at medium range you are not going to get the effect you think you want. It just isn't physically possible without a certain type of lens. My suggestion, with what you have is to push the zoom in a bit farther.

I have a Pentax MZ-7 film camera and while it has served me well I'm hitting up digital in a very short while because I'm sick of the levels of control I'm losing from film to developing to printing.