From the course: Learning Underwater Photography

Momentary auto and manual focus - Photoshop Tutorial

From the course: Learning Underwater Photography

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Momentary auto and manual focus

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- [Instructor] In this movie, we're going to talk about two other focus modes that are available to you, Momentary Autofocus and Manual Focus, both of which give you an even higher degree of control. - [Instructor] So Momentary Focus is a little bit of a hack of the autofocus system of your camera. So basically, what we're doing is we're removing the focus from your shutter button, so when you push that shutter button all it's going to do is take a photo, regardless of whether the subject is in focus or not. What we're going to do is we're going to reassign that focus function to another button, and depending on the camera model and manufacturer, there's a variety of buttons that we can choose to do that. So what that means is autofocus will only be activated when you're pushing that button. So let's say, for example, that we assign the autoexposure lock or autofocus lock button that you can see here on the back of a Nikon DSLR. We could assign that button to be the focus button. So as long as we're depressing that button, autofocus will be activated, but as soon as we release the button autofocus is no longer active. So what this allows us to do is this allows us to use basically a combination of autofocus and manual focus. We can focus on our subjects, and then as long as we're not moving the camera very much, we can take a rapid-fire succession of photos without having to wait for the camera to re-autofocus every time. So this can be especially useful when we're doing things like what we like to call over-under photos or split shots. With an over-under photo, the camera's sticking sort of half in and half out of the water, and we're capturing a scene above the water and below the water. With images like this, focus point is critical, and we don't really want to rely, as we're trying to lift the camera a little bit out of the water, that it's still trying to autofocus and we miss our shot. So by using a momentary autofocus method, we can focus on the foreground subjects such as the reef underneath and then once it's in focus, since we're not moving very much, as we're lifting that camera in and out of the water and taking the shots, we don't have to worry about the camera losing focus. - [Instructor] And so obviously this would be a disaster if you were relying on continuous autofocus, for example. - [Instructor] Absolutely. We want to make sure that the focus point and the focus are not changing while we're taking the scene. - [Instructor] And you were saying you'd pick and autofocus point underwater before you lifted up the camera? - [Instructor] I would focus using the momentary autofocus, focus on the point that I know is acceptable for the image, and then basically not focusing again unless I noticed that it wasn't quite right the first time. - [Instructor] But what I'm wondering is, would you do it underwater, or would you do it over, or does that largely depend on... - [Instructor] Absolutely, you want to be focusing underwater for split images. - [Instructor] And that brings us to manual focus. - [Instructor] Manual focus does exactly what it says on the tin. It allows you to manually choose the point of focus for the camera. Now, normally this would require some interaction with the lens on the camera. To perform this in a housing, we actually need to have an additional focus gear that affixes on to the lens of the camera and then the housing has to have a corresponding knob that's going to allow us to turn that gear. - [Instructor] And so where the housing is concerned, this is pretty complicated. When Hergen mentions gear, he means a real gear that attaches to your lens, and you've got to get it on there to exactly the right position so the gear that's assigned to whatever kind of control you have outside the housing locks into alignment. - [Instructor] Now, there are certain cameras that allow you to access manual focus electronically. Such as some combat cameras. But the big benefit of manual focus is it allows precise control of focus, and this is really really going to come into play when we discuss supermacro later on. - [Instructor] And absolutely, because what you often find yourself doing, especially if you're a bit of an amateur like me, is you lock down your focus on this macro creature, on this very small creature, and then you find yourself drifting ever so slightly depending on your buoyancy, at which point you have to manually tweak the focus. And that's our look at momentary autofocus enhanced by manual focus in the world of underwater photography.

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