focus on two subjects.

[gingrjenny]

I found this video that may help others with DOF.


it talks about the role of distance and focal length as well as f stop on dof. It made it a little clearer for me... A little!

 

[gingrjenny]

When I zoomed out to 18mm it took the iso down to 650 being the same distance from the subject. I looked at some of the other photos and the iso ranged from 650 to 6400 (yikes) having it on auto. I did shoot in raw that day and had my whitebalance set to daylight. I was in aperture priority mode.

 

[Redeyejedi]

I found this video that may help others with DOF.


it talks about the role of distance and focal length as well as f stop on dof. It made it a little clearer for me... A little!

a decent shooting experiment you can do to help you see it: 3 sets of shots at 3 static subjects spaced apart and from a set distance. First set of shots focus on each subject and maintain same aperture. second set, forcus on farthest subject, changing aperature for each shot(3), and thrid set focus on near subject and change only aperture. evaluate the results and it. this helped me 'get it' many' years ago, but i had to wait to see the results following day when we processed the film. if i miss-worded the experiment/test, sorry, but that is roughly how i remember it. hope it helps.

 

[cynicaster]

View attachment 50274
This photo I took I feel like they were both at about the same DOF. But one is more in focus and the little boy is blurry. f/6.3, 1/125, iso 1600(i had it set on auto)

I think what you meant to say here was that the children are at "about the same distance from the camera" not at "about the same DOF".

As mentioned, DoF is one of the trickier fundamentals to get your head around. You just have to keep at it and it'll sink in eventually.

One thing to keep in mind is that wherever you focus, there will be a certain distance in front of and behind that point that will be "acceptably sharp", with the larger portion being behind.

If you have a Canon crop-sensor camera with a 50mm lens set to f/5.6, and you stand 10 feet away, you should have plenty of DoF to get two kids situated as shown in your example. To be safe, and if there is light to spare, you might want to hit f/8.

so If I focus on what is closer the area behind should be more in focus. So if I would of changed to f/8 I would of had to slowed down my shutter speed even more? I was already at high iso.

To be clear, the area behind isn't "more in focus" than the area in front. What I was trying to convey is that there is more distance behind the focus point that is acceptably sharp than there is in front of the focus point. That's just how the physics work.

If you have depth of field to spare (which you would, if you opted for f/8 in my previous example), you can focus on the closest subject and everything will be fine. If, however, the depth of field is just large enough to get the eyes of both kids in focus, then if you focus on the eyes of the closest subject, the other subject won't be sharp. Why? Because the portion of the available depth of field in front of the focus point is wasted on empty space, and you're relying upon the portion behind the focus point to get everything, and there won't be enough.

And yes, changing the aperture from f/5.6 to f/8.0 makes the "opening" in the camera smaller, letting in less light, so to get the equivalent exposure, the shutter would need to be open longer or the ISO would need to be bumped up.

 

[gingrjenny]

I think what you meant to say here was that the children are at "about the same distance from the camera" not at "about the same DOF".

As mentioned, DoF is one of the trickier fundamentals to get your head around. You just have to keep at it and it'll sink in eventually.

One thing to keep in mind is that wherever you focus, there will be a certain distance in front of and behind that point that will be "acceptably sharp", with the larger portion being behind.

If you have a Canon crop-sensor camera with a 50mm lens set to f/5.6, and you stand 10 feet away, you should have plenty of DoF to get two kids situated as shown in your example. To be safe, and if there is light to spare, you might want to hit f/8.

so If I focus on what is closer the area behind should be more in focus. So if I would of changed to f/8 I would of had to slowed down my shutter speed even more? I was already at high iso.

To be clear, the area behind isn't "more in focus" than the area in front. What I was trying to convey is that there is more distance behind the focus point that is acceptably sharp than there is in front of the focus point. That's just how the physics work.

If you have depth of field to spare (which you would, if you opted for f/8 in my previous example), you can focus on the closest subject and everything will be fine. If, however, the depth of field is just large enough to get the eyes of both kids in focus, then if you focus on the eyes of the closest subject, the other subject won't be sharp. Why? Because the portion of the available depth of field in front of the focus point is wasted on empty space, and you're relying upon the portion behind the focus point to get everything, and there won't be enough.

And yes, changing the aperture from f/5.6 to f/8.0 makes the "opening" in the camera smaller, letting in less light, so to get the equivalent exposure, the shutter would need to be open longer or the ISO would need to be bumped up.

I think I understand...but the photo has to be in focus to be sharp. right?

 

[Tinderbox (UK)]

Canon had a setting on it`s older dslr called A-DEP for some reason they stopped including it with their newer dslr`s , would this have helped keeping both kids in focus.

John.

 

[Gavjenks]

Canon had a setting on it`s older dslr called A-DEP for some reason they stopped including it with their newer dslr`s , would this have helped keeping both kids in focus.

John.

Something like this might still be possible with custom firmware such as Magic Lantern. Or not. I never read all the way through their 400,000 page manual. It certainly COULD be done with firmware if not.

 

[cynicaster]

so If I focus on what is closer the area behind should be more in focus. So if I would of changed to f/8 I would of had to slowed down my shutter speed even more? I was already at high iso.

To be clear, the area behind isn't "more in focus" than the area in front. What I was trying to convey is that there is more distance behind the focus point that is acceptably sharp than there is in front of the focus point. That's just how the physics work.

If you have depth of field to spare (which you would, if you opted for f/8 in my previous example), you can focus on the closest subject and everything will be fine. If, however, the depth of field is just large enough to get the eyes of both kids in focus, then if you focus on the eyes of the closest subject, the other subject won't be sharp. Why? Because the portion of the available depth of field in front of the focus point is wasted on empty space, and you're relying upon the portion behind the focus point to get everything, and there won't be enough.

And yes, changing the aperture from f/5.6 to f/8.0 makes the "opening" in the camera smaller, letting in less light, so to get the equivalent exposure, the shutter would need to be open longer or the ISO would need to be bumped up.

I think I understand...but the photo has to be in focus to be sharp. right?

Yes. I just used the term “acceptably sharp” rather than “in focus” because it underlines the fact that there is only one distance from the camera that will be in “perfect focus”, and from there, every millimeter you move closer to the camera or farther away from it will gradually get more and more out of focus. The rate at which this happens is dependent on several factors. There is a lot of math and gobbledygook that would be required for a rigorous explanation of how this works, but in a hands-on situation, there’s no need for you to care about most of that stuff. All you’re interested in knowing is what you can do to increase or decrease the number of inches, feet, or whatever you have on either side of the focus point where the focus is still “acceptably sharp”. The size of this “buffer zone” is the so-called “depth of field”.

With all else being equal:

• If you use a larger aperture (a numerically smaller f/number) your depth of field gets shallower (smaller)
• If you physically move closer to the subject you’re trying to focus on, the depth of field gets shallower
• If you use a longer focal length (i.e. “more zoom&#8221, the depth of field gets shallower

It’s easy to see how it gets tricky; a lot of times you’ll make changes to all of these factors at once, so it can be tough to get your head around what the net effect will be.

 

[bratkinson]

I am not one that thinks of the exposure triangle as a set of ‘hard and fast rules/numbers/settings’. I tend to be a more ‘casual’ about it than most photographers. Perhaps that’s one of the advantages of being an amateur rather than pro photographer.

Instead, I think of ‘I want more of xxx, so I need to increase (or decrease) yyy’ to get it. Yes, I could count the clicks when I make adjustments. (Let’s see…4 clicks smaller aperture…3 clicks slower shutter plus 1 click faster ISO to compensate…no, wait…2 + 2 will work…no…maybe 1 + 3&#8230 Instead, I take the shot after making the adjustments I think should work for what I want, then look at the histogram to see if I need to fine-tune it a bit and shoot again.

For example, when I want a very thin DOF, perhaps only in inches, I know I have to shoot ‘wide open’, or close to it, with whatever lens I want to use for the shot. Generally speaking, the super-thin DOF needs a lens like f2.8 or ‘faster’ (smaller f-stop number = larger aperture), as well as being ‘reasonably close’ to the subject. That’s because even without changing the lens or the camera settings, as the distance to the subject (focus point) gets smaller, the DOF gets smaller, too. Simply moving back a few steps can double the depth (‘thickness’, if you will) of the DOF. Of course, opening up the aperture requires speeding up the shutter speed and/or slowing down the ISO speed to keep the proper exposure.

In situations where I want perhaps 10 feet of DOF for a group shot, I know I need to have the aperture ‘somewhere in the middle’, perhaps f5.6 or f8, maybe even f10 (2/3 stop). Alternatively, I could step back to perhaps 25-30 feet from the subject and shoot at maybe f4, but I also want to consider what I’d have to do with the shutter speed and ISO to compensate, and what effects those changes would have on the picture.

One of the biggest challenges I face is that most of my photography is taking pictures of people indoors at church functions. That means I need at least 1/125[SUP]th[/SUP] shutter speed and faster, to stop any possible subject-motion caused blurring (and camera motion, as well). While the general rule of 1/<focal length> shutter speed works adequately to stop camera shake, dealing with people/pets/moving subjects requires that faster shutter speeds are needed. Trying to stop an airplane at takeoff would likely require 1/1000 or faster. Even &#8216;posed&#8217; subjects tend to move/blink/breathe, so 1/125[SUP]th [/SUP]&#8211; 1/160[SUP]th[/SUP] is my usual shutter speed for that. But that shutter speed requires A LOT of light when shooting indoors, or a fast ISO (1600 and faster). More light = wider open aperture which causes a thinner DOF. Faster ISO results in more noise which degrades the picture, although it is correctable to some degree in post processing. I HAVE done no-flash photography at slower speeds like 1/20, 1/30, or 1/60 to keep a &#8216;reasonable&#8217; DOF, aperture, or ISO, but sometimes the limits of &#8216;reasonable&#8217; are &#8216;bent&#8217; to accommodate. Also, at those speeds, there is frequently subject and/or camera motion blurring, so the keeper rate is in the neighborhood of 1 in 10 or less! Multiple shots are therefore necessary. Using a flash solves most of the indoor lighting problems, but there are some venues it&#8217;s not allowed (church ceremonies, typically). Flash use then adds a variety of new problems, especially in terms of shadows which can be dealt with by having it off camera, remotely triggered, bounced, having multiple flashes, etc.

In the end, it what it comes down to is deciding what I want to focus on/emphasize in the picture - stop action, deep DOF for a group shot, etc &#8211; then determine what I &#8216;must do&#8217; in the exposure triangle to get it&#8230;usually choosing only one (1) of the three parts for &#8216;must do&#8217;. The other two settings of the triangle often fall into place, but many times, there have to be compromises made to &#8216;get the picture&#8217;.