Determining the Minimum Focusing Distance

PrimaryCanary · Aug 15, 2006

Forum Members,

I am considering a new lens. Since I don't have access to trying the lens out before I buy it (it's a pricey canon lens and the local camera shops don't stock it) I am trying to compare what it will "frame" like using my existing lens.

The specifications for the lens state the minimum focusing distance is 18.84 inches. How do I measure this? Is that 18.84 inches from the digital sensor inside the camera body or is that 18.84 inches from the end of the lens (the external glass of the lens)?

This makes a difference because I want to make sure that I can fill the frame with this lens before I decide it's a good purchase. Given the above information I can make an informed decision as to how the lens will "frame".

Any help is greatly appreciated.

Thanks.

964 · Aug 15, 2006

Which lens is it? Furthermore, I am not sure I understand your question. I mean, with my 70-200 and the 2x TeleConverter I get a focal length of 400mm. The minimum focus distance on this lens is maybe 1 metre or say 36 inches but if I were to zoom right in at 36 inches I should be able to 'frame' just the retina of someone's eye.......on my 16-35 if I focus at 1 metre distance I could get 3 heads in the frame possibly....so if I understand your question correctly it willdepend on the focal length of the lens (and the crop factor on your camera - which is 1.6x by the way - I used to have one, great camera).

ksmattfish · Aug 16, 2006

PrimaryCanary said:
This makes a difference because I want to make sure that I can fill the frame with this lens before I decide it's a good purchase. Given the above information I can make an informed decision as to how the lens will "frame".

Most of my lenses seem to measure the min focus distance from the end of the lens, but I'm not sure that's the way every lens manufacturer does it. Filling the frame isn't just minimum focusing distance, but angle of view also. The least complicated way to check is to find a store that stocks the lens, put it on a body, and look through it. Other than that, get out your protractor and ruler, I guess.