Lens length help

Dangermouse

Dangermouse

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I will shortly be putting my Siggy 400APO on ebay but I want to know the exact focal length it is on a dslr and 35mm film with a 2x converter
Thanks for any help given
 
andrewc said:
Exact focal length will be 400 and 800mm regardless of 35mm or DSLR as focal length doesn't change.
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I always thought that sa a 100mm lens was a 105mm on a dslr and so on ....so I can say its a 400mm lens with a 2x tc giving 800mm and not get caught out by unscrupulous buyers thats good :thumbs:
 
The Nikon 2DH has a crop factor of 1.5.

To calculate the actual focal length of you lens when used on the 2DH is a case of multiplying the focal length 400mm by 1.5 giving an equivalent of 600mm on a 24x36 full frame sensor( digital or Film)

Add a 2x converter and the equivalence is 1200mm minus 2 stops.


Hope this helps
 
Surely its an equivelant focal length? Because by having the crop factor you arent any closer, but the image is cropped as if it was as close as focal length X Crop factor.

Personally I would just say its 400mm and 800mm with the 2xTC otherwise you just confuse people :p

Regards, James
 
Holden Caulfield said:
The Nikon 2DH has a crop factor of 1.5.

To calculate the actual focal length of you lens when used on the 2DH is a case of multiplying the focal length 400mm by 1.5 giving an equivalent of 600mm on a 24x36 full frame sensor( digital or Film)

Add a 2x converter and the equivalence is 1200mm minus 2 stops.


Hope this helps
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B****y hell I will be lost lol anyway its posted on ebay as simply a 400mm siggy

But thanks for taking the time to check this out for me I am sure I will need the info soon
 
Jamesbuk said:
Surely its an equivelant focal length? Because by having the crop factor you arent any closer, but the image is cropped as if it was as close as focal length X Crop factor.

Personally I would just say its 400mm and 800mm with the 2xTC otherwise you just confuse people :p

Regards, James
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Focal length is focal length is focal length - digital or film it doesn't change as it is a physical characteristic of the lens (zooms changing as you physically alter the element calibration within the lens)

What people often confuse with focal length is field of view (or FOV) which changes between all formats; 35mm film, digital sensors (many different within here), medium format, large format
 
Yea, as rick says, people will just call it a 400mm regardless otherwise it just confuses the situation.
You only need to think of the difference if you had a full frame body, or both (crop and FF) because then it would appear longer on the crop body. So just think of 400 and 800mm's not 400x1.6=600mm every time lol.
 
So just think of 400 and 800mm's not 400x1.6=600mm every time lol.
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Good point , however ,

Before the advent of digital, focal length was straight forward we used a 50mm lens on 35mm and a 75-80mm lens on large ( 120) format and we called these ‘standard lenses.

Anyone could get a lens guide and see comparisons in focal length , usually done by shooting the same subject from a fixed distance with a variety of lenses of differing focal lengths.

With the advent of digital sensors in SLR cameras things became confusing, these sensors were smaller than the 35mm 24x 36 format consequently the prescribed view of focal length altered.

An example being myself after buying my first digital slr body was elated that all my tele lenses gave more reach, things appeared closer.

This elation soon waned when I discovered that my wide angle lenses had now less field of view due to the cropping factor.

The other dynamic which seldom gets a mention is the age old rule of keeping shutter speeds above the focal length of the lens when shooting hand held, this helps reduce camera shake.

Relying on the traditional view of focal length without factoring in the crop factor of you camera’s sensor can lull the photographer in to a false sense of security leading to the loss of valuable images from camera shake.
 
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