Canon zooms with Infrarad focusing markings?

[david_boily]

Hi,

 

I'm looking for a Canon EF zoom that will have the IR focusing

markings. It needs to have a 58mm or 62mm filter thread and the

wider it goes the better (also the cheaper the better).

 

I'm new to Canon and there seems to have been so many EF zooms over

the years that I have no idea where to start. Anyone know which

models fit this description?

 

Thanks

[photojim]

Even the ones that have the marks won't have them for all focal lengths, which reduces a lot of the incentive to use a zoom lens.

 

L-glass zooms probably don't need refocusing. The L indicates fluorite (low dispersion) glass, which provides accurate focusing of all colours at one point - usually including infrared, which is just beyond red in the spectrum. (Ditto for Nikon ED, except that Nikon uses special extra low dispersion glass that isn't made of fluorite.)

[jim_leonard]

funny, my 70-200/2.8 L has such markings

[bobatkins]

Many "L" series lenses have IR focus marks, especially wider angle lenses, but some medium telephotos too. It's just not true that "L" lenses (even those with fluorite elements) are achromatized for IR wavelengths

<p>

The 28-105/3.5-4.5 has IR focus marks for 28, 35, 50 and 105mm and it takes 58mm filters. This is your best bet, around $200 and an excellent general purpose lens too.<p>

 

 

Note that IR focus marks are at best a guide, not a totally acurate way of focusing. Alter all IR covers a pretty wide spectrum from 700nm to maybe 900nm, depending on what film you use and what filter you use, so one mark doesn't really cover every possible combination. Testing for yourself and using a small aperture to give good DOF is always advisable. Also some Canon lenses will shift focus for themselves when used with an IR filter since the AF sensor is IR sensitive. Again you need to test with your lens/filter/film combination.

<p>

If you order one, please consider using one of the links on the <a href="/">photo.net home page </a>that take you to retailers who support photo.net (Adorama, B&H, Ritz).

[andrew robertson]

One technique that I find useful when shooting IR is to 'focus bracket' your

shots. Set up your camera on the tripod, shoot a frame at the 'correct' focus,

and then shoot one more with front focus, and one more with back focus. It's

a bit more expensive, but I assume that that's not a huge issue (or else you

probably wouldn't shoot IR at all). You'll get a feel for the focus adjustments

you need to make with a certain film and certain lens combination as you

shoot with them.