How to Figure Out What ISO to Use
I am at a place in my shooting career (I’ve been shooting about 34 years) that I can break all the rules to get some interesting results. I have to say, though, that you have to know the rules in order to break them. So let’s go over what an ISO is and how to manipulate it to get some results that might not be deemed “ordinary”.
First of all, in film photography, we had ASA which was the indicator of how sensitive a film was to light. If you’ve seen film before or (hopefully) worked with it you’ll see numbers like 100, 200, 400 and 800. The lower the number, the finer the grain but the more light you need to expose the film.
So now that we are mostly shooting digital, ASA has been replaced with ISO which basically measures the sensitivity of the image sensor and the same rules that applied in film photography apply with digital: the lower the number, the less sensitive to light and the finer the grain.
So you need to amp up your ISO when you’re shooting in darker situations so you can get a faster shutter speed in order to not have a complete set of blurry images. So for instance, you’re shooting in a studio (indoors) and you don’t want to use much light and your model is moving and you want to freeze her movement. So you ramp up your ISO pretty high. But what happens with high ISO is that you usually get a lot of noise (the new-age word for grain). As Dana points out, we don’t use our cameras on auto settings anymore, right?? So when you use a higher ISO, you need to adjust your aperture and shutter speed.
So let’s recap this: If you’re shooting in a well lit situation and you don’t want any grain or noise, you can use a relatively low ISO. If you are shooting in less light situation and/or you want more grain, you bump up your ISO.
The biggest dilemma with most people is the noise factor. And that’s where my old-school “Original Gangster break all the rules and don’t give a fuck”-self emerges and tells you all that I love the grain. So it’s a matter of preference. Those super glossy Gucci Mert and Marcus ads have relatively zero grain. They are sharp as fuck and there’s more light (and retouching but never mind I said that) than known to the inventor of light himself, God.
Myself, on the other hand, tend to covet the works of Deborah Turbeville and Paolo Roversi, where they probably used to boil their negatives back in the day to produce even more grain (yep….I’ve done it too and it turned out beautiful once you get the technique down).
A very common situation for me is that I’ll be on set, my assistants will set the lights up where I tell them to, everything’s set and we start do lighting tests. I become very unhappy with the look so I start turning off the lights. Most of the time, I’ll turn off the strobe and just use the modeling lights as the key source of light. I’ll amp up my ISO and shoot the whole story at 2,000 ISO.
For instance, one of my favorite shoots in the last few years was the Kurv Magazine shoot where I had a set built to replicate a chapel. We lit the shit out of that small set, putting softboxes on the outside of the fake windows, beauty dishes on the models and we even had candle light. I was so frustrated with the lighting test that I just turned off the strobe feature on the Profoto packs and then did my lighting tests. It looked exactly how I wanted it.
I have always been a less is more fan with my lighting. And more grain or noise doesn’t bother me. I think the beauty and the drama in an image is in the shadows.
Of course, if I’m shooting for a client, then I have to abide by what they want and I’ll choose the appropriate ISO for that particular gig.
Native ISO settings are what the camera companies deem as the optimum settings for your particular camera. This tech stuff is way over my head and I’m not going to lie, I rely on my assistants to help me figure this stuff out now. I crammed 20 years of education and knowledge on how to expose, develop and print black and white and color film. I was pro at it. Digital is lost on me a bit, maybe part of the reason is I’m just not that interested in the process but I know a lot of you are. I found a good article on Native ISO settings for Canon and Nikon on SLR lounge.
Here are two examples of a low (normal) ISO and then a pretty high ISO. Yes, there is more noise on the second shot. And I like them both. But you can become even more of a master by being able to manipulate the shoot you are shooting by playing around with the ISO’s and creating out of the norm images.