canon 35mm f2 is usm

[kevin2]

can anyone tell me what the fixed marks 22 11 and the red dot on the focus ring indicator signify

[Waddizzle · Accepted solution]

The numbers are an aperture settings.  They are showing the approximate depth of field at those aperture settings.  As you vary the focus, you can read off of the focus ring how deep the DoF would be.

The lens in the image is focused at the hyperfocal distance.  I am not sure about the red dot.  

[kevin2]

Thanks

[RobertTheFat]

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@Waddizzle wrote:

The numbers are an aperture settings.  They are showing the approximate depth of field at those aperture settings.  As you vary the focus, you can read off of the focus ring how deep the DoF would be.

The lens in the image is focused at the hyperfocal distance.  I am not sure about the red dot.  

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It appears to me that the lens is focused at infinity, not at the hyperfocal distance. I think that the two numbers to the left of the vertical bar point to the hyperfocal distances at f/22 and f/11 when the lens is focused at infinity.

[kvbarkley]

The red dot is for infrared focus, because the wavelength is different, you need to focus at a slightly different point. It does not mean much for a DSLR. 8^)

[ebiggs1]

Now for the correct answer.

The white lines are the DOF, or hyper focus, you use the hyper focal distance scale to know which parts of your image will be in focus at different aperture settings.  The red dot is used to adjust the focus if you're shooting using an infrared filter. When set to infinity the focus ring is turned slightly to the left so that the infinity marking appears in line with the red dot. For 99% of us it is useless. The side ways "L" is a variable infinity because infinity can come at slightly different places depending on several factors.

[shadowsports]

Red dot on hyper focal distance scale.

Good questions.

Its the infrared focusing mark.  Believe its a carry over from days gone by.  With infrared film you actually had to focus at a different place than normal because the infrared spectrum of light is different than what we see with our eyes.  No idea how to replicate digitally, but I guess it can still be done. 

*****All 3 of us posted over one another  LoL

[ebiggs1]

"*****All 3 of us posted over one another"

It would seem so. 

In fact most lenses don't have many marks on them at all anymore.

[kevin2 · Accepted solution]

Thanks everyone. Appreciate your help and knowledge

[kvbarkley]

The cool adaptive LCD display on my 70-300 II does not have an infrared mark. 8^)

I am hoping for a firmware update so that it will show the hyperfocal distance.