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Old Jan 5, 2006, 9:35 PM   #1
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While walking in the woods the other day, I stopped to take a shot of a weathered fence & tree with ivy growing on them. I shot it in manual with a Minolta A1 at an aperture of f4. As you can see, the Depth of Field at f4 was too great (& rendered the forrest floor, of leaves & ivy) as too "in-focus".

In this particular case, I would have been better off stopping down the aperture of f3.5 or 3.0. Although, I can probably go into Photoshop & make some corrections, I try to shoot as-close-to-usable images in-camera. Just an observation, from someone who continus to learn....
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Old Jan 7, 2006, 10:06 AM   #2
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In a bizarre way I kind of like of like that shot.

You're right, controlling te background is key to good photography.


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Old Jan 8, 2006, 3:47 AM   #3
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Opening up the lens as you suggest would reduce the depth of field. Shooting at the maximum telephoto on the zoom will also help reduce depth of field.

However most digital compact cameras have small sensors and therefore short focal length lenses. This means that depth of field tends to be quite large at all apertures.
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Old Jan 8, 2006, 9:43 PM   #4
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True. I was shooting with a Minolta A1, 5MP camera (not your normal compact digital). Here's the EXIF info for that shot:

14.5mm
57mm (in 35mm film)
Subject dist: 2.00m
1/40 sec, f/4
Mode: Manual
Metering: Center-weighted average
ISO: 100
White balance: Auto
Flash: Off
File size: 223KB
Image size: 600 x 480
Saturation: High
Sharpness: Normal
Contrast: Low

This 2nd image was shot a little while later & here's the EXIF info for it:

76.2mm
300mm (in 35mm film)
Subject dist: 1.50m
1/60 sec, f/5
Mode: Manual
Metering: Center-weighted average
ISO: 100
White balance: Auto
Flash: Off
File size: 77KB
Image size: 600 x 480
Saturation: High
Sharpness: Normal
Contrast: Low

Even though I was using a larger aperture (of f5.0)...I shot it at a longer focal distance.
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Old Jan 8, 2006, 11:25 PM   #5
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I'm just trying to understand this.... I've got a Canon A85 with a Manual setting where I can control the shutter speed and apature. Problem is, everything I read about it is confusing, and experimenting with different settings seems to produce very similar photos (no recognizable difference).

I if I was trying to take a portrait with the background blurred, I'd lower the apature? Would I have to adjust the shutter speed?

I'd love to learn about apature and shutter speed for these kinds of effects. I don't like the telephoto option as camera-shake becomes more of an issue than it already is.

Any advice? Thanks in advance.
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Old Jan 9, 2006, 10:19 AM   #6
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Each F stop lets in half as much light as the next one in the scale. The largest F stops that let in the most light are the smaller numbers so F2 lets in twice as much light as F2.8 which lets in twice as much as F4 and so on.

To blur the background you need larger apertures so the smallest number your camera will allow.

Because each aperture lets in different amounts of light you have to alter the shutter speed to change the amount of time that the sensor is exposed so that the exposure stays the same.

Say for example you have a scenethat can be shot at F2 and 1/500 second you can also shoot it at F2.8 1/250, F4 1/125, F5.6 1/60 or F8 1/30. As you see each time you reduce the aperture you double the length of time the shutter is open.

The problem with digital cameras is that they have lenses which a very short focal length. On the A85 this is 5.4mm to 16.2mm. The depth of field is affected by focal length as well as aperture and the shorter the focal length the greater the depth of field at any aperture. With a maximum focal length of 16.2mm you're always going to have a fairly broad depth of field. The Minolta A1mentioned in the previous post has a longer maximum focal length used at 76.2mm in the example. At this focal length a large aperture will give a shallow depth of field.


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Old Jan 9, 2006, 11:19 AM   #7
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Thanks Nagasaki. I think I'm catching what you're talking about, although it's still a bit technical. I'm not exactly sure what you mean by "focal length," but I think it refers to what's in focus.

style="BACKGROUND-COLOR: #000000"The problem being that no matter what I set my apature to, the pictures don't seem to change. Meaning, I'm trying to mimic a picture I saw of a butterfly in a book, where the butterfly itself is in focus while the background is blurry. But no matter how low or how high I set the apature value to, the pictures all come out looking more or less the same.
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Old Jan 9, 2006, 11:55 AM   #8
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Focal length is the a feature of the lens. The A85 has a zoom lens that can change it's focal length from 5.4mm for wide angle through to 16.2mm for telephoto.

Depth of field refers to how much is in focus. When you focus any lens you focus it to a certain distance say 1 metre. If you have a shallow depth of field maybe only 99cm to 1 metre 1cm is in focus. With a large depth of field everything from 1 metre to infinity may be in focus.

Generally it's the aperture which controls the depth of field but lenses with a short focal length will always have a greater depth of field than a longer focal length lens at any aperture.

If you had 35mm film camera you'd need a 35mm-105mm lens to get the same zoom range as your A85. The 35mm lens would have less depth of field at all settings than yoyr A85 lens because even though it gives the same field of view it is a much longer focal length lens.

What this means is that with digital compact cameras it is almost impossible to recreate the type of shallow depth of field shot you describe.


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Old Jan 9, 2006, 12:05 PM   #9
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So there wouldbe a significant difference between my A85 and a D-SLR, or even an S2 IS, when it comes to taking photos like what I've described?
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Old Jan 9, 2006, 1:46 PM   #10
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Yes the S2 IS has a maximum focal length of 72mm and with a DSLR the choice is yours but all but the very wide angle lenses would give less depth of field at large apertures.
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