Faking Spot metering

[ext3eleven]

I've read in some photography site and found out that you can spot meter even if your slr/dslr doesn't have spot metering functions.
Only applies for zoom lens though.

"Note, however, that partial metering is very much like a fat spot meter - you can use it in a similar fashion in many cases. Also, if you have a zoom lens you could zoom in to your metering point, meter with the partial meter, and then zoom out. The result is that you’ll be metering from a small area, just like a real spot meter."

http://photonotes.org/articles/beginner-faq/cameras.html

 

[roygoh]

1. You need very long focal length to be metering from a small enough area that is comparable to a real spot meter.

2. The zoom needs to maintain constant max aperture throughout the entire zoom range. If not, you will be metering at a smaller effective aperture when you zoom in.