Recommendations: IR Glass Filter

DonRicklin

If I were to get one good quality IR Glass filter for which lens should I get it? My Sigma 17 - 70mm, 2.8 - 4.5 (72mm lens size) or my Sigma 24 -135, 2.8 - 4.5 (77mm lens size). I have already ruled out the 70 -300.

Not looking to do a body conversion at this time.

Don

ziggy53

Don,

The best thing to do is choose the filter size based on the maximum filter size you might need and then us an adapter to reduce the filter to fit smaller filter threads.

For example, I have a filter that I wanted to use with 2 lenses, one which uses 77mm filter threads and one which uses 67mm filter threads. I bought the filter with 77mm filter size and threads and use a 67mm-77mm "step-up ring" when I want to use the filter on the lens with 67mm threads.

Not all lenses are equally suitable for IR use and I don't know if any of your lenses are suitable or not. Some lenses have a problem in the IR spectrum producing a "hot spot", sometimes pronounced, which may cause extra processing and sometimes makes a lens unsuitable for IR work. The hot spot may also vary by both lens and camera combination.

I recommend researching your lenses first before committing to an expensive high-quality IR filter.

As an example, see the following link for some recommendations:

http://photography-on-the.net/forum/showpost.php?p=5222723&postcount=7

DonRicklin

Thanx, Ziggy53! I had actually thought of the step ring option. Just more stuf to carry.

I'll have to see if I can 'borro' a filter to chek on hot spots before buying. Do you think this kind of info might be kown by a B&H salesman with respect to my lenses?

Don

ziggy53

DonRicklin wrote:

... I'll have to see if I can 'borro' a filter to chek on hot spots before buying. Do you think this kind of info might be kown by a B&H salesman with respect to my lenses?

Don

Almost certainly not, I'm afraid. The manufacturers do not publish IR compatibility and, because it varies by camera and lens combination, you almost have to find others with equipment just like yours. If you can borrow an IR filter to test, so much the better.

pathfinder

Be aware that some very good lenses ( even L lenses ) are poor choices for IR shooting as they cause hot spots in the image

There is a good discussion of this phenomenon here

I learned this the hard way - the Canon 85mm f1.8 is a great lens for normal shooting, but a lousy lens for IR work.