On wedding days, we’re often shifting between wide open and narrower apertures, because we’re alternating between shooting individuals and groups, and between shooting still subjects and movement. One minute, we’re photographing just the bride, so we want a lower/wider aperture because we know we can nail the focus and get a beautiful creamy background that way. The next minute, we’ve got a handful of bridesmaids in the mix, and we’ll want a narrower one (higher number) to ensure every face is in focus. During the ceremony, we start with people walking down the aisle, most importantly the bride and her father, so again, we want that narrower aperture again to guarantee we’re getting our moving subjects in focus. But, when the ceremony starts and the bride and groom, bridal party, family, and guests are all relatively still, we’ll want a wider (lower number) aperture. It’s a constant balancing act where we’re asking ourselves this question:

How wide can I shoot to get everything I need in focus while getting as much as I can creamy in the background? 

Or, to phrase it differently:

What’s the lowest my aperture number can be to get everything I need in focus while getting as much as I can blurred in the background? 

So, today, we’re going to talk about how we’re able to change apertures on the fly without needing to re-meter our cameras or, in some cases, even take a test shot — although we do whenever we can!

Now, there are a lot of ways to do this, and none of them are right or wrong. It’s all about preference. But, as former teachers, we know that everyone’s got a different learning style, way of doing things, and system that makes them comfortable, so if this helps you, then great! If you’ve got a different or better way to go back and forth between apertures while still keeping your exposure perfect, that’s awesome, too! It never hurts to see another perspective, we believe, because you’ll either learn something new or it’ll reinforce what you already know, so you’re a winner either way!

Let’s use a real life example to make this come alive:

You’re at a wedding photographing a bride at f/2.8 (the aperture), ISO 100, and a shutter speed of 250. Then, the bridal party walks up and now you’re shooting a larger group. So, you line the girls up and decide that f/4.0 is a safe aperture to get everyone in focus and still give you enough depth so that there’s some blur.

Question: What can you do without re-metering or looking at your LCD screen to keep your exposure exactly the same?

Answer: Click your ISO to 200.


It’s important to remember that your camera’s three exposure settings — aperture, ISO, and shutter speed — operate in a series of full stops separated by 1/3 stops — or three clicks of the wheel.

So, as an example, going from f/2.8 to f/4.0 is one full stop. And, in between each full stop, there are 1/3 stops as well. Maybe seeing it this way will help:

f/2.8   Full Stop

f/3.2   1/3

f/3.5   2/3

f/4.0   Full Stop


When it comes to ISO, we leave our Canon cameras set to only show us native ISOs — 100, 200, 400, 800, etc. — which double each other with each click and, therefore the camera’s sensitivity to light. For example:

If you go from ISO 100 to 200, you’re telling the camera to let in twice as much light or be twice as sensitive to the light coming into the camera.

If you go from ISO 200 to 100, you’re doing the opposite and telling the camera to cut the amount of light coming into the camera by half.

We like these ISO setting on our cameras because it allows us to VERY quickly let light flood into our cameras if we need to get a grab shot, like at this weekend’s wedding, when we were photographing our bride only a few feet away from floor to ceiling windows in the hotel room when her mom walked through the door into the entryway that, just by the look of it, was at least twice as dark as where we were photographing. Fortunately, all we had to do was take our ISO a few clicks and we had two to four times the brightness that we had near the window and a pretty well-exposed photos with no time to really think or react.

Just to reiterate, if you’re using native ISOs on your camera, then you won’t have 1/3 stops available anymore. One click will jump you one full stop. So, instead of there being 125 and 160 in-between ISO 100 and 200, there’ll just be 100 or 200. That’s important to remember since your aperture and shutter speed will still function on a series of 1/3 stops where each click of the wheel equals 1/3 stop and 3 clicks of the wheel equals a full stop.

Shutter Speed

The camera’s shutter speed operates in third stop increments, too. So, for example, if you went from a fasted shutter speed of 1/200 of a second down three clicks to 1/100 of a second, essentially allowing twice the amount if light into your camera, the 1/3 stops in between would look like this:

1/200   Full Stop

1/160   1/3 Stop

1/125   2/3 Stop

1/100   Full Stop

Now that we’ve got that covered, you’ve probably figured out what you need to do to answer the original question:

Question: What can you do without re-metering or looking at your LCD screen to keep your exposure exactly the same?

Answer: If you cut the amount of light going into your camera in half or by a full stop by taking your aperture from f/2.8 to f/4.0, then you have to balance that by allowing twice as much light to come into your camera another way, either with ISO or shutter speed.

So, if you go from f/2.8 to f/4.0, it’s not a problem, as long as you bump your ISO from 100 to 200.

The exposure will stay the same.

The next time you’re out shooting, get there a few minutes early and test this out to see it for yourself. Even though in most cases you’ll be able to look at your LCD screen to double-check yourself, having this base knowledge and comfortability will make you a stronger photographer and will help eliminate some of the guess work you might find yourself doing from time to time.

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filed in: Education


    Awesome breakdown! When I'm shooting I still get flustered when change happens quickly. This is going to come in very handy :)

    Amy & Jordan

    So glad it helped, Christin!

    Tim Poole

    When I learned photography and taught photography, and this was all film at the time, this was one of the basic concepts that had to be locked down, especially since everything was set manually. ("Today, class, we are introducing the 'Law of Reciprocity'." It was worth it just to watch their eyes roll back in their heads.)
    So I was shocked, I say shocked! when your first piece of advice was to change the ISO setting. I was getting ready to give you a snooty, I am smarter than you post, when it finally dawned on me...one couldn't change the ISO of the film that was in the camera.
    So thanks for the great tip.

    Amy & Jordan

    Thanks, Tim! This means so much coming from someone with your level of experience and expertise! We hope that we can connect with you again at a photographer event in Phoenix :-)

    Brealyn Nenes

    This simple post has helped me SO much! Amy and Jordan: You're awesome.

    Amy & Jordan

    Aw! We are SO glad!! :)

    Mel B

    This was explained so beautifully! Thank you so much.

    Amy & Jordan

    Thank you, Mel!! So happy to help!!

    Karen Rolla

    This is the best explanation Ice ever seen. Thank you so much

    Amy & Jordan

    Aw, you're so sweet! We're so glad to help.