What is the meaning of the red words?

[hwchoy]

learn something new everyday man

 

[khairi]

hmmm...from what i tried last time, I tried street shooting using 28-105 hyperfocused once. this was what i concluded, might be wrong, might be right.

The Red markings is to show the range where your lense will hyperfocus to infinity at the
various focal lengths. Then, the aperture value will ensure the DOF that you want.

Eg: move the infinity marking to Red Mark 50. Thus, (me assume) 10m to infinity will be the
hyperfocus range for the lense, and sharpest will be between both markings.
Then your selected aperture will determine the DOF that would be in the hyperfocused
range.

 

[hwchoy]

hmmm...from what i tried last time, I tried street shooting using 28-105 hyperfocused once. this was what i concluded, might be wrong, might be right.

The Red markings is to show the range where your lense will hyperfocus to infinity at the
various focal lengths. Then, the aperture value will ensure the DOF that you want.

Eg: move the infinity marking to Red Mark 50. Thus, (me assume) 10m to infinity will be the
hyperfocus range for the lense, and sharpest will be between both markings.
Then your selected aperture will determine the DOF that would be in the hyperfocused
range.

hey berry, no lah the red marks turn out to be for infrared ah.

 

[yanyewkay]

you can find it on almost all the old prime lens.

my shooting weapons not that old and also not that many also.. first time i seeing this ;p

 

[lsisaxon]

come on lar...
I'm not the only one shoot IR, anyway, nikon af lens don't have IR marking also.

ED and APO lenses don't need IR markings because the focusing point is the same as visible light.

 

[lsisaxon]

this leads to another question I have in mind after reading catchlight's post that it was IR markings and 2nd confirmed by you. Why have markings for IR?

very useful for catchlights but for others?

Because the refractive index for the glass used is not the same for IR and visible light. This is a dispersion effect.

 

[hwchoy]

ED and APO lenses don't need IR markings because the focusing point is the same as visible light.

well the 28-135 definitely not ED/APO. the magic drainpipe also have this marking, even though it uses UD elements.

 

[hwchoy]

Because the refractive index for the glass used is not the same for IR and visible light. This is a dispersion effect.

to add on, because IR being the longest wave, gets dispersed the most relative to the other wavelenghts.

 

[catchlights]

ED and APO lenses don't need IR markings because the focusing point is the same as visible light.

yes, your are right, I forgot about this, also forgot about what kind of lens I use.
just check the 17~55 and 18~70 don't have, and 50f1.8 have, and I remember saw it on the 24~85 f2.8~4 lens, but the tamron 90mm and tokina 12~24 don't have IR making also.