Focus Length


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jameseka

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Apr 24, 2007
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I just got this nikon D40 with 18mm to 55 mm and I plan to purchase a longer range lens.

I when though my previous photo that was shot using olympus C5050 with nikon picture project to see what range I normally took.
The focus length from various photo is inbetween 5.6mm ( wide angle ) to 23mm ( telephoto)

Now I am confuss and do not know whether should I go for max range of 135mm or 200mm.
How to convert the foucs length to the exact figure.
 

ihub88

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Mar 3, 2007
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#2
get a 70-200 will do.

range covered.
 

scenar

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Aug 23, 2005
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I just got this nikon D40 with 18mm to 55 mm and I plan to purchase a longer range lens.

I when though my previous photo that was shot using olympus C5050 with nikon picture project to see what range I normally took.
The focus length from various photo is inbetween 5.6mm ( wide angle ) to 23mm ( telephoto)

Now I am confuss and do not know whether should I go for max range of 135mm or 200mm.
How to convert the foucs length to the exact figure.
The focal lengths u see now do not have a common "reference pt". Normally, the field of view associated with a focal length is "normalized" to that of a full frame DSLR / 35mm film camera to make apples to apples comparisons easier.

This is done by multiplying a certain "crop factor" for other cameras like your D40 and your olympus C5050. The smaller the sensor, the higher the crop factor.

D40 - crop factor of 1.5
C5050 - crop factor of 5-6 (not sure)

Thus the field of view for the
(1) 18-55 lens is approx that of a ~27-82mm lens (on full frame/film)
(2) C5050 has an equiv field of view to a ~28-105mm lens (on full frame/film)

To extend your range, u could consider the 55-200vr or 70-300vr
Don't forget to multiply the focal length numbers u see on the box by 1.5
 

surge

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Mar 17, 2002
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#7
on e C5060 ( or other compact), the CCD sensor is small. thus even though e long end is only 23mm , the sensor is so small that it can only capture the very center portion of the image, thus view becomes about 80mm of a 35mm film. now that you are on D40, forget about the FL of olympus...since sensor size is already different.
 

jameseka

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Apr 24, 2007
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#8
Thank all for the above information.
 

zoossh

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Nov 29, 2005
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#9
I just got this nikon D40 with 18mm to 55 mm and I plan to purchase a longer range lens.

I when though my previous photo that was shot using olympus C5050 with nikon picture project to see what range I normally took.
The focus length from various photo is inbetween 5.6mm ( wide angle ) to 23mm ( telephoto)

Now I am confuss and do not know whether should I go for max range of 135mm or 200mm.
How to convert the foucs length to the exact figure.
check the conversion factor for your pns, usually is 5x-6x whereas DSLR usually 1.3-2x.

supposed it is 6x, you are shooting till 130mm which is about 90mm actual focal length on the DSLR with 1.5x conversion factor.

you are google or look into dpreview. but i suggest that yuou just try out in the shop. sigma/tamron 18-200 (or nikon if you have more cash). i'm not sure if the kit lens up to 135 in D80 is sold separately.

remember for D40, your lens must have motor to run autofocusing.
 

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