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Old Jan 19, 2007, 3:11 PM   #11
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Eric S, thanks for the info, but it actually proves my point. As you've pointed out, a 100mm lens has 1/10 the DOF as a 50mm at the same distance. This means that with the 100mm, if you stepped back to twice the distance to achieve the same composition of the subject, according to the calculator you linked to the DOF would be exactly the same. Therefore, since the out of focus area is enlarged 2 times, the background would be 2 times as blurry, which is closer to the effect Slaman is trying to achieve.

Coincidentally, now that I'm looking at some of the original posts, this is pretty much what you said to do in your original post, so I guess we're not really in disagreement. The only difference really is to the point of view of a point and shoot user who is more used to shooting a person's face up close with little zoom, I'm saying to that person they need to step back and zoom more. Obviously you don't want to tell someone to get closer and zoom more when they are already on top of their subject.

Here are a few more sources that also say to use as much focal length as possible:

http://digital-photography-school.co...grounds-right/

http://www.wikihow.com/Create-Those-...hoto-Portraits

http://www.lifehacker.com/software/p...its-159432.php

Thanks for the info. I'll be bookmarking that link.

Yeah, Ray Harryhausen was a master of the art. Now-a-days when you watch the credits to a movie like Pirates of the Caribbean, the names of special effects companies and artists goes on and on. But in movies like Jason and the Argonauts and Clash of the Titans, it was pretty much just Ray.
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Old Jan 19, 2007, 10:11 PM   #12
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Zoom as far as your camera can go. If you can get a telephoto attachment lens, than can help as well. Technically this doesn't decrease your depth of field, it just enlarges everything so that a slight blur appears to be a much greater amount of blur.
Corpsey, I realize where my problem was. I took the above quote to mean that you said more telephoto won't increase DOF. But in reading it again, that isn't what you meant. What you were saying was that the telephoto attachment lens won't increase the DOF. That I'll agree with.

It is an interesting question of which makes more of a different. With the same framing but using more focal length (and standing further away) or standing closer and using a wide angle.... Let see what the calculator says:

Canon 30D, 50mm, f/8, 25 feet away 29.2 ft
Canon 30D, 100mm, f/8, 50 feet away 24.3 ft

This assumes that the above settings produce the same field of view, which I think they do.
It looks like focal length effects depth of field more than distance... but I think the interrelations between DOF, distance & focal length is non-linear. When I used shorter numbers (5 and 10 feet) the different in DOF was 0 (both were 0.9 ft.)

What I was suggesting was that if slaman didn't have a particular image in mind, then the best way to get the smallest depth of field was to *both* get close and use a lot of focal length. This combination will produce the smallest DOF. But it might not produce the desired image - which is a problem I wasn't taking into account.

I don't think that slaman was trying for more blur, but was trying for a smaller DOF. Maybe I was reading it wrong.

Eric
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Old Jan 20, 2007, 5:31 AM   #13
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slaman,

Something like this?

Fuji S5100, 1/480, F5, ISO 64, max zoom (370mm equivalent), macro mode.

the Hun

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Old Jan 20, 2007, 8:47 AM   #14
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eric s wrote:
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Zoom as far as your camera can go. If you can get a telephoto attachment lens, than can help as well. Technically this doesn't decrease your depth of field, it just enlarges everything so that a slight blur appears to be a much greater amount of blur.
Corpsey, I realize where my problem was. I took the above quote to mean that you said more telephoto won't increase DOF. But in reading it again, that isn't what you meant. What you were saying was that the telephoto attachment lens won't increase the DOF. That I'll agree with.

It is an interesting question of which makes more of a different. With the same framing but using more focal length (and standing further away) or standing closer and using a wide angle.... Let see what the calculator says:

Canon 30D, 50mm, f/8, 25 feet away 29.2 ft
Canon 30D, 100mm, f/8, 50 feet away 24.3 ft

This assumes that the above settings produce the same field of view, which I think they do.
It looks like focal length effects depth of field more than distance... but I think the interrelations between DOF, distance & focal length is non-linear. When I used shorter numbers (5 and 10 feet) the different in DOF was 0 (both were 0.9 ft.)
When your focus point starts to get closer to the hyperfocal distance, you will start seeing a difference.

But, at most shooting distances where you'd be more concerned about blurring a background, you'll have the same depth of field, regardless of your focal length, as long as the aperture and subject framing (percentage of the frame occupied by the subject) remains the same.

Here is an article on the subject (although Michael doesn't go into how the Hperfocal distance factors in, you can see how it factors in when using a DOF calculator).

http://www.luminous-landscape.com/tutorials/dof2.shtml

But, because of the perspective difference you get from shooting at further distances for the same framing when using a longer focal length, you'll have a more compressed background, even if the actual DOF is identical.

This difference in perspective gives the illusion of a shallower depth of field (which is why a longer focal length is typically used to blur backgrounds, even though the actual DOF may not be changing).


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Old Jan 20, 2007, 9:02 AM   #15
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Is it really only possible to get depth-of-fields shallow with a Digital SLR?
That's mostly dependent on the size of your subject, the percentage of the frame you want the subject to occupy, and the distance to the background.

The problem is that a non-DSLR model can use a much shorter focal length lens for any given angle of view (because the sensors in a non-DSLR model are much smaller). So, you'll have much greater depth of field for any given aperture and subject framing with a non-DSLR model.

This question comes up pretty often. So, I'll copy most of this reply from another thread:

http://www.stevesforums.com/forums/v...mp;forum_id=28

Zoom in as much as possible and get closer, framing tighter, putting as much space between the subject and background as possible. Then, use larger apertures (smaller f/stop numbers) shooting in Av (Aperture Priority) mode.

The reason you have more Depth of Field with a non-DSLR digital camera is because of the actual focal length of the lens being used with a smaller sensor.

As a result of a very tiny sensor compared to 35mm film, the lens on most digicams can have a much shorter actual focal length, to get any given 35mmequivalentfocal length (i.e, the same angle of view as you'd have with the lens on a 35mm camera).

That's how they can make an "ultra zoom" type camera that is so small.

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 much 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) helps - but this is usually not enough to achieve the desired results for larger subjects with most non-DSLR models (i.e., your people photos, unless you go with a tight head shot).

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).

The perspective changes from using more optical zoom (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

Sbooting small, subjects from close distances is one thing. Trying to blur the background with larger subjects is something else entirely (since you need to be further to get them fitted in the frame, increasing depth of field).

That's one of the appeals of a DSLR (the ability to control Depth of Field for helping your subjects stand out from distracting backgrounds). The sensors are just too small for that in non-DSLR models (unless your shooting smaller subjects).

A non-DSLR model with much greater depth of field can be a good thing, too.

You may want more depth of field versus less, and with a DSLR model, you'd need to stop down the aperture (smaller aperture represented by higher f/stop numbers) to get it (often requiring much higher ISO speeds or slower shutter speeds to achieve what you can get with a non-DSLR model shooting at wide open apertures.

There are pros and cons to both types of systems.


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Old Jan 30, 2007, 8:04 AM   #16
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I think the subject/topic gets confused. We can talk of "Bokeh" (beautiful out of focus area) or"shallow depth of field" (DOF).
I have found most times that the description can be moot if what is sought after is a subject that literally "POPS" off the background, so distinctly separate that the subject is the only thing that counts.

So when you look here:

http://new.photos.yahoo.com/[email protected]/0

or the URL below:

http://new.photos.yahoo.com/[email protected]

you see the different variations on the theme.

Of course a beautiful "Bokeh" (out of focus) areabehind the subject is really what is sought whether we call it shallow depth of field or "Bokeh".
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