Some questions on zoom lenses


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Dec 18, 2004
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#1
Hi all. New to this so pardon my ignorance. I've been using a simple digital camera and am beginning to get interested in the SLR. However the zoom range mentioned for digital cameras are mostly like 10x or 3x. The SLR lenses go by ranges like 28-80mm and so on. How would i know the distance I can zoom with an SLR lens. Is there a guide of some kind?
 

JLLJ

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Jun 17, 2003
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#2
All the compact digital camera has a fixed lens (not changable). The 10X/3X etc is calculated by the farthest zoom (tele) divided by the widest angle, it is just a ratio. This is not accurate to use this to tell -- for a fixed distance, how wide the angle your camera can cover; since most compact camera's widest angle is 35 mm (equivalent to SLR) while some more expensive compact have 24-28mm at the widest angle.

In SLR (35 mm) term, the angle of view (the left most to the right most angle of thing you can capture on film) can be represented by the focal length of the lens (in mm). The smaller the focal length, the wider the angle (object appears smaller in the frame); and the longer the focal length (telephoto) the narrower is the angle and the object appears larger as it now fill up the 35 mm frame.

Since SLR can change lens, the size of image appear on the film is related to the object size, the distance of camera from your subject and the focal length of your lens.
Normally 28mm is suitable for small group photo, ie. at wedding dinner, 50mm for 3/4 to half body portrait and 85 mm for shoulder & head portrait. To shoot small object at very far distance ie. small bird you'll need super telezoom like 300mm and above. film SLR (35mm) with 28mm-80mm is sufficient for almost all normal street photography; remember that you will still need to adjust your distance between your camera and the subject to get different effects. Standing at one place and just zoom in/out produce more boring photos.

For Digital SLR (DSLR) there is another muliplier to the focal length to take care of because the digital sensor is smaller than the 35mm film. (you can check your compact digicam that the focal lenth is in range of only few mm only because the sensor is tiny) So the smaller the sensor, the larger the multiplier to your lens focal length to be equivalent to the SLR.
With the multiplier, the angle of view become narrower, ie, 50 mm lens will become 50 x 1.5 = 75mm lens.

Back to your question of "How I know the distance I can zoom with an SLR lens"; it all depends on far is your subject vs how big you want your subject to appear. I can take a picture of same subject with 28mm at close distance vs 200mm at a far distance and the subject appears the same size in the picture. However, the perspective and distortion to the photo will be very different.

Hope the above help, though may appear more confucing to you, but to fully understand needs multiple factors to consider. I'm also in the process of learning.
 

Jun 27, 2002
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#3
JLLJ said:
All the compact digital camera has a fixed lens (not changable). The 10X/3X etc is calculated by the farthest zoom (tele) divided by the widest angle, it is just a ratio. This is not accurate to use this to tell -- for a fixed distance, how wide the angle your camera can cover; since most compact camera's widest angle is 35 mm (equivalent to SLR) while some more expensive compact have 24-28mm at the widest angle.

In SLR (35 mm) term, the angle of view (the left most to the right most angle of thing you can capture on film) can be represented by the focal length of the lens (in mm). The smaller the focal length, the wider the angle (object appears smaller in the frame); and the longer the focal length (telephoto) the narrower is the angle and the object appears larger as it now fill up the 35 mm frame.

Since SLR can change lens, the size of image appear on the film is related to the object size, the distance of camera from your subject and the focal length of your lens.
Normally 28mm is suitable for small group photo, ie. at wedding dinner, 50mm for 3/4 to half body portrait and 85 mm for shoulder & head portrait. To shoot small object at very far distance ie. small bird you'll need super telezoom like 300mm and above. film SLR (35mm) with 28mm-80mm is sufficient for almost all normal street photography; remember that you will still need to adjust your distance between your camera and the subject to get different effects. Standing at one place and just zoom in/out produce more boring photos.

For Digital SLR (DSLR) there is another muliplier to the focal length to take care of because the digital sensor is smaller than the 35mm film. (you can check your compact digicam that the focal lenth is in range of only few mm only because the sensor is tiny) So the smaller the sensor, the larger the multiplier to your lens focal length to be equivalent to the SLR.
With the multiplier, the angle of view become narrower, ie, 50 mm lens will become 50 x 1.5 = 75mm lens.

Back to your question of "How I know the distance I can zoom with an SLR lens"; it all depends on far is your subject vs how big you want your subject to appear. I can take a picture of same subject with 28mm at close distance vs 200mm at a far distance and the subject appears the same size in the picture. However, the perspective and distortion to the photo will be very different.

Hope the above help, though may appear more confucing to you, but to fully understand needs multiple factors to consider. I'm also in the process of learning.

:thumbsup: :thumbsup:
 

CLQ

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Jan 31, 2005
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#4
JLLJ said:
All the compact digital camera has a fixed lens (not changable). The 10X/3X etc is calculated by the farthest zoom (tele) divided by the widest angle, it is just a ratio. This is not accurate to use this to tell -- for a fixed distance, how wide the angle your camera can cover; since most compact camera's widest angle is 35 mm (equivalent to SLR) while some more expensive compact have 24-28mm at the widest angle.

In SLR (35 mm) term, the angle of view (the left most to the right most angle of thing you can capture on film) can be represented by the focal length of the lens (in mm). The smaller the focal length, the wider the angle (object appears smaller in the frame); and the longer the focal length (telephoto) the narrower is the angle and the object appears larger as it now fill up the 35 mm frame.

Since SLR can change lens, the size of image appear on the film is related to the object size, the distance of camera from your subject and the focal length of your lens.
Normally 28mm is suitable for small group photo, ie. at wedding dinner, 50mm for 3/4 to half body portrait and 85 mm for shoulder & head portrait. To shoot small object at very far distance ie. small bird you'll need super telezoom like 300mm and above. film SLR (35mm) with 28mm-80mm is sufficient for almost all normal street photography; remember that you will still need to adjust your distance between your camera and the subject to get different effects. Standing at one place and just zoom in/out produce more boring photos.

For Digital SLR (DSLR) there is another muliplier to the focal length to take care of because the digital sensor is smaller than the 35mm film. (you can check your compact digicam that the focal lenth is in range of only few mm only because the sensor is tiny) So the smaller the sensor, the larger the multiplier to your lens focal length to be equivalent to the SLR.
With the multiplier, the angle of view become narrower, ie, 50 mm lens will become 50 x 1.5 = 75mm lens.

Back to your question of "How I know the distance I can zoom with an SLR lens"; it all depends on far is your subject vs how big you want your subject to appear. I can take a picture of same subject with 28mm at close distance vs 200mm at a far distance and the subject appears the same size in the picture. However, the perspective and distortion to the photo will be very different.

Hope the above help, though may appear more confucing to you, but to fully understand needs multiple factors to consider. I'm also in the process of learning.
Good explaination mate :)

cheers-
 

IvT

New Member
May 9, 2005
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#5
JLLJ said:
All the compact digital camera has a fixed lens (not changable). The 10X/3X etc is calculated by the farthest zoom (tele) divided by the widest angle, it is just a ratio. This is not accurate to use this to tell -- for a fixed distance, how wide the angle your camera can cover; since most compact camera's widest angle is 35 mm (equivalent to SLR) while some more expensive compact have 24-28mm at the widest angle.

In SLR (35 mm) term, the angle of view (the left most to the right most angle of thing you can capture on film) can be represented by the focal length of the lens (in mm). The smaller the focal length, the wider the angle (object appears smaller in the frame); and the longer the focal length (telephoto) the narrower is the angle and the object appears larger as it now fill up the 35 mm frame.

Since SLR can change lens, the size of image appear on the film is related to the object size, the distance of camera from your subject and the focal length of your lens.
Normally 28mm is suitable for small group photo, ie. at wedding dinner, 50mm for 3/4 to half body portrait and 85 mm for shoulder & head portrait. To shoot small object at very far distance ie. small bird you'll need super telezoom like 300mm and above. film SLR (35mm) with 28mm-80mm is sufficient for almost all normal street photography; remember that you will still need to adjust your distance between your camera and the subject to get different effects. Standing at one place and just zoom in/out produce more boring photos.

For Digital SLR (DSLR) there is another muliplier to the focal length to take care of because the digital sensor is smaller than the 35mm film. (you can check your compact digicam that the focal lenth is in range of only few mm only because the sensor is tiny) So the smaller the sensor, the larger the multiplier to your lens focal length to be equivalent to the SLR.
With the multiplier, the angle of view become narrower, ie, 50 mm lens will become 50 x 1.5 = 75mm lens.

Back to your question of "How I know the distance I can zoom with an SLR lens"; it all depends on far is your subject vs how big you want your subject to appear. I can take a picture of same subject with 28mm at close distance vs 200mm at a far distance and the subject appears the same size in the picture. However, the perspective and distortion to the photo will be very different.
good good... help me understand some perspective issues too :thumbsup: :thumbsup: :thumbsup:
 

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