apertures

[corkymiller]

Why is there no f2 between f1.4 and f2.8 on my f1.4 lens yet my f2 lens also goes to f2.8 as the next stop? I thought every stop was a double or half the size of the one next to it. How can f2.8 be half f1.4 and f2?

 

[Pgeobc]

Some sort of way to lower the cost of production, I suppose.

 

[KmH]

A full stop is f/1.4 to f/2. Most DSLR cameras are set by default to adjust aperture in 1/3 stop steps, but can be set up to do 1/2 stop or full stop steps.

You don't say what lens you are referring to.

 

[480sparky39 38]

It's probably not there because there isn't room for it.

f/2 to f/4 is two full stops, not one. It's a formula, not a mathematical progression.

 

[Garbz]

Are you talking about a physical lens or on the camera. Old lens with an aperture right or newer?

On a digital camera you should have an f/2 to chose from along with f/1.8 and f/2.2 on either side.

Physical lens aperture rings have historically had 1 stop intervals. They run up standard values f/1.4 f/2 f/2.8 f/4 f/5.6 f/8 f/11 f/16 f/22. On older lenses with aperture rings they were limited by physical mechanical clicks which slide the aperture blades into place. Some lenses like the f/1.8 however were 1/3rd of a stop more open at f/1.8 than f/2 which is the next standard number and you would actually feel that the very first click on the aperture ring was very short before it got back into it's normal scale. However there was never enough space on the aperture ring to write f/2 next to f/1.8 so while you could physically click it over to f/2 it wasn't marked. Same applied to f/1.2 lenses which had f/1.2 then f/2 marked even though f/1.4 was the next click to be felt.

On digital SLRs this is meaningless. The camera can actuate the aperture blades to arbitrary values which is why on AF Nikkors the manual asks you to lock the aperture ring to the smallest setting to allow the aperture blades to stop all the way down if requested. Because of the arbitrary settings most cameras give you a choice on scales. 1/3rd stops or 1/2 stops. They look like this:

1.0 1.2 1.4 1.7 2 2.4 2.8 3.3 4 4.8 5.6 6.7 8 9.5 11 13 16 19 22 for the half stops
1.0 1.1 1.2 1.4 1.6 1.8 2 2.2 2.5 2.8 3.2 3.5 4 4.5 5.0 5.6 6.3 7.1 8 9 10 11 13 14 16 18 20 22 for the third stops

 

[jasonphoto]

Some sort of way to lower the cost of production, I suppose.

hmm really?