ZI lenses and IR markings

[AusDLK]

I just received my second ZI lens. I know own silver 35mm Biogon and 50mm Sonnar lenses that are a great match for my souped up M3. (Actually an M2/M3/M4 hybrid now.)

I was pleased to see the ZI lenses have the IR focus markings.

 

[ronnie_retro]

Now, if only we had IR film to go with markings! ;-)

Seriously, that stuff seems to have disapppeared from the market. I was planning on picking up some of the Macophot but it seems to have been discontinued. But at least we're ready...

 

[AusDLK]

I have a freezer full of HIE and EIR.

Enough to last me a little while whenever I get back to an IR project.

 

[RML]

The IR markings also work well with my R-D1. I reckon they'll work a charm with that IR gobbler, the M8. 😛

 

[ronnie_retro]

Zinger, RML!

 

[AusDLK]

> I reckon they'll work a charm with that IR gobbler, the M8.

Don't get me (re)started on that dog... For my sake and the forums! 😉

 

[butter71]

I was pleased to see the ZI lenses have the IR focus markings.

i'm clueless on shooting IR. how does one use IR focus markings?

 

[rxmd]

i'm clueless on shooting IR. how does one use IR focus markings?

Basically any focusing action has to be offset by the angle between the IR and normal focus marks.

Focus normally. Look at your distance scale. The distance you're focusing at is next to the normal focus mark now. Turn the focusing ring slightly so that this point is next to the IR focus mark instead of the normal focus mark.

Philipp

 

[AusDLK]

This is really only an issue if you use opaque IR filters...

Since IR radiation (ie., light rays) has a longer wave length than visible light it focuses at a different point.

Since you use your eyes to focus using light in the visible spectrum the focus point is not accurate for non-visible light.

So, focus normally, note the distance indicated at the normal point on the lens, rotate the focus ring so the indicated focus point now rests opposite the (normally) red IR focus mark, and you have properly focused for IR.

If you are using a sufficiently small f-stop so that depth-of-field covers the IR focus point, do nothing.