By Steve Kozak

It’s simple math, really. Let’s see how you do on the following:
110/5 = ?
110/10 = ?
110/20 = ?

Now, was that really so hard? If you round the answers to a number that corresponds to the nearest f-stop on your lens, then you are ready to create extremely accurate exposures with your portable flash.

Yes, you just learned how to use “guide numbers”.

Guide number/distance = f-stop.

But no more.

I just learned that this timeless, dare I say, “elegant” way of calculating the exposure of a portable flash – without having to use a light meter, has been removed from the test specifications for the CPP exam.

I’m guessing with the proliferation of photographers using TTL and flashes that have become so “easy” for anyone to use if they can put it on the camera facing in the right direction, they will get “acceptable” images. I just never strived for “acceptable”. As a wedding photographer, I hated under-exposed bridal portraits and over exposed groomsmen all because TTL tries to give an “average 18% grey” exposure. That is why in 33 years as professional photographer, I NEVER used TTL.

I tolerated the laughs and teasing I took because I use guide numbers. “Who still uses guide numbers?”, I would often hear. “I guess, photographers who like proper exposure.”, I would quip.

Now, I am not griping about guide numbers being removed from the exam, I am really questioning my own existence. I have taught thousands of photographers how to use a flash in manual mode the same way I learned to use a flash. It always worked. It never failed. Images were never over or under-exposed. All I had to do was quick, easy math.

But now, we are taking guide numbers off the CPP exam.

I once heard, “If you don’t like change, you’re going to hate extinction.”

Do I have to change my teaching because our industry feels guide numbers are no longer relevant? Or do I go the way of the dinosaur and just let them die off with me and keep pressing young photographers to learn the ways of their forefathers?

What should this dinosaur do?

Steve Kozak