1. ## Question about wording in most recent issue

On page 49 of the June 2012 issue, in the top left corner you have the verdict for the Canon 70-300L lens. The wording is, "A superb performer as long as you avoid apertures smaller than f/16."

On second read, I understand it now. You mean f/22 is smaller than f/16. I thought you mean smaller f-number, which would've been ridiculous.

2. Yes it is confusing. Do we mean physically smaller physical diameter, or lower value number? I even confuse myself sometimes. Glad you figured it out!

3. ## f-numbers

Perhaps the time is right for the magazine to explain how f-numbers came about, and why a larger aperture has a smaller f-number.

The answer is quite simple, of course, because the numbers we see printed are, in fact, reciprocals, i.e. the focal length of the lens (f) divided by (/) a number (n), which is why it is printed f/n.

For example, a 50mm lens with a 25mm aperture is described as f/2; or a 50mm lens with a 12.5mm aperture is described as f/4. Obviously we do not know the physical size of the aperture, (we cannot get inside the lens and measure it) but the results of these calculations help us to work out how much light the lens is letting through.

To simplify things further, consider ¼ and ½; anyone with a basic knowledge would know that ¼ is smaller than ½, but if these figures were printed with the letter 'f' replacing the figure '1', i.e. f/4 and f/2, one could possibly think that 4 was greater than 2.

Can we have an article, please, in simple terms?

4. ## f-stops

Editor - I printed my reply, above, in large letters, hoping to have some reaction from you or your staff. Should I have printed it bigger still?

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