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Old Sep 6, 2005, 8:31 AM   #1
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Can you achieve the same focus as you can with a 35mm SLR? I mean when I focus with my 35mm SLR (a vintage Canon TL) my subject is in focus but everything else is blurry. I have tried to do it with my digital and no luck. :? Any advice?

Thanks!!!!:G
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Old Sep 6, 2005, 9:40 AM   #2
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Yes, it works the same.

The problem you may be having is that unless you have a Digital SLR with a good lens the camera usually has a fairlysmall aperture resulting in greater depth of field.
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Old Sep 6, 2005, 9:42 AM   #3
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Get closer, frame tighter.

The reason you have more Depth of Field with a non-DSLR digital camera is because of the actual focal length of the lens. You didn't mention your camera model, but non-DSLR cameras have sensors that are very tiny (much smaller than 35mm film).

As a result, the lens on most digicams can have a much shorter actual focal length, to get any given 35mmequivalentfocal length. Look at the front of your lens and you'll probably see the actual focal length printed (along with it's aperture ratings for the wide angle and full telephoto zoom positions).

So, your subject occupies a much larger percentage of the frame at any given actual focal length, compared to a 35mm camera at the same distance to subject with most digicams.

For any given 35mm Equivalent Focal Length, you'll have dramatically more Depth of Field compared to a camera with a larger sensor (or film).. This isbecause Depth of Field is computed by the actual versus 35mm equivalent focal length,focus distance,and aperture.

Your ability to blur the background for any given aperture depends on your subject size, the percentage of the frame you need it to occupy (which you can use focal length or the distance to your subject to change), and the distance to the background that you want your subject to stand out from. Of course, using the largest available aperture (represented by the smallest f/stop number) is needed-- but this is usually not enough to achieve the desired results for larger subjects with most non-DSLR models.

Your best bet is to frame as tightly as possible (fill the frame by getting in closer or using more zoom). In other words, go for a tight head and shoulders, versus a full length shot. You'll want to use the camera's largest available aperture (smallest f/stop number), and put as much distance as possible between the subject and background.

You could also try focusing in front of the subject (so that your subject is barely in the area of acceptable sharpness).

Load this Depth of Field Calculator and selectyour camera model. Then, plug in the *actual* focal length of the lens, focus distance and aperture to calculate Depth of Field.

http://www.dofmaster.com/dofjs.html

Of course, keep in mind that when you use more optical zoom, you'll need to be further away from your subject for it to occupy the same percentage of the frame (hence, cancelling out thebenefits of longer focal lengths in some shooting conditions where you'd want less Depth of Field, especially since the largest available aperture requires the wide angle lens position with most compact digital cameras).

Although the perspective changes (more compressed background from shooting further away), can give the illusion of a shallower depth of field, since blur in out of focus areas will be more obvious (even if the real depth of field isn't changing, since you need to take the photo from further away if you use more zoom for the same framing).

So, for many scenarios, unless you can budget for a DSLR model (which have much larger sensors compred to non-DSLR digital cameras), your best bet is to try and use software to simulate a shallow depth of field. You may want to check in theEditors forum to get some tips. Here is a thread with a couple of different methods mentioned:

http://www.stevesforums.com/forums/view_topic.php?id=29694&forum_id=31

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Old Sep 6, 2005, 10:03 AM   #4
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One more point, if your p&s camera has a big zoom, use it, the DOF will decrease.
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Old Sep 6, 2005, 10:13 AM   #5
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On the bright side, because of the smaller sensors you have with most non-DSLR digital cameras, it's easier to get more depth of field when you need it.

You can always simulate a shallow depth of field using software to blur a background (of course, how good the results look depends on your tools and skill level).

But, it's kind of hard to increase depth of field later with software if it's too shallow because you can't stop down the aperture enough for some subjects in many lower light conditions with your 35mm camera, at least not with most color film.

This is because even ISO 1600 film may not be enough to get shots of non-stationary subjects you could get with a small sensored digicam at ISO 200 in lower light, because shutter speeds will still be slower than the digicam's if you stop down the aperture enough with your 35mm to match it's Depth of Field. If you want more versus less depth of field, a compact digicam can be better ;-)

So, there are pros and cons to a smaller digital camera.

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Old Sep 8, 2005, 2:33 PM   #6
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Thanks for all the tips. I admit I am not a professional; I usually just put my canon tl on f2.8 and the shutter speed on 250 or 500. It is pretty easy to get excellent shots.I love my digital(panasonic lumix fz5) and use it all the time. It takes reallyquick pictures and they look great. I think I will just use the slr when I want a professional looking portrait.

Thanks again!

Heather
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Old Sep 9, 2005, 7:20 PM   #7
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I took this with a Minolta 7i, set at about f4.0 (I think). A P&S type of digital camera generally allows less control (with some always focusing on infinity).
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Old Oct 27, 2005, 4:13 PM   #8
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Brandnugirl,

Kalypso is right about P&S digitals having less control over depth-of-field than DSLRs, but I have had good luck with blurring the background of some of my existing photos with image editing software (I use Paint Shop Pro 7&8, but certainly you can do the same with the Photo Shop versions as well as Elements and others).

Essentially, you would use the freehand selection tool to select your foreground subject feather the selection and invert it to encompass the background; then use a blur filter to blur the background a little bit or apply a more aggressive blur with the filters for a more pronounced effect.

For a simple tutorial on this effect using Paint Shop Pro, see the link to Richie Dumlao's excellent site below. While you're there check out the several other photo manipulation tutorials he has there.

http://www.pinoy7.com/psptutorials/1.../default.shtml

This effect is particularly effective when you have a photo with a good subject and a rather busy background that you want to blur. I have saved several photos this way and it's fun to experiment!
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Old Nov 7, 2005, 8:54 AM   #9
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Wow, great pic!! Thanks a lot, I will definately try!!

Thanks again
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Old Dec 5, 2005, 5:41 PM   #10
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Shallow depths-of-field are also more easily achieved when taking pictures of small objects. These were taken with my FZ10:

http://www.airshowfan.com/digicams/mantis2.JPG

http://www.airshowfan.com/digicams/ladybug.JPG

This is because of the scaling-down that JimC was talking about. If the PROPORTIONS between sensor (or film) size, focal length, and distance-to-subject are preserved, so will the depth of field relative to the distance to the subject (all other things - like aperture - being equal).

In other words, say you take a shot with a film SLR and the shot has a shallow depth of field. Now say you take a digital camera with a sensor 1/6 the size of the piece of film, and with a lens whose focal lengths are 1/6 those of the film SLR (same aperture "f" numbers, which are already relative to the focal length, and so are also smaller in absolute dimensions by the same factor, in this case 1/6). For you to get the same depth of field at the same equivalent focal length, your subject needs to be 1/6 the distance from the camera and be 1/6 the size, so that all the proportions are preserved with the new, smaller focal length. (Of course, a person cannot become 1/6 the size... I'm just saying this as a thought experiment).

Notice it's harder to get shallow depth of field in an SLR if your subject is really far away. If your subject is at a great distance from you, then the subject and the background focus very similarly. With a digital camera whose sensor and lens are 1/6 the size as in an SLR, the distance where this happens is only 1/6 as far away. (Not that there is a critical distance where this happens. I know it's gradual. But you get what I'm saying).
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