Hopefully a basic ‘focusing’ question

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124
Name
Will
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#1
Hi guys,

I have a Canon 70D

Last weekend I went out shooting for the first time. I shot some friends in their new clothing brand.

Half my pictures were in focus and half weren’t

And I don’t know why!

Maybe because I was snapping too quick and not half pressing the shutter?


When shooting a single model what AF point setting should I use?

Also, when shooting a group of people, say 3 people stood next to each other. How do I get them all in focus but using an F stop of 1.8.

Which AF point should I use?


I don’t use manual. Not really learnt yet.

I use AV

thanks guys
 
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252
Name
James
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#2
someone far more experienced than me will be along shortly im sure and will correct me if i go a little wrong.

F1.8 has a narrow depth of field so will only have a small range where the point of focus is sharp in focus. Unless its low light i would suggest using a larger aperture (f Stop). I have recently realised the mistake of trying to use the lowest f stop and alot of the time its not needed. Did you try using a higher F stop say 5.6?
 
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willkia
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124
Name
Will
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#3
someone far more experienced than me will be along shortly im sure and will correct me if i go a little wrong.

F1.8 has a narrow depth of field so will only have a small range where the point of focus is sharp in focus. Unless its low light i would suggest using a larger aperture (f Stop). I have recently realised the mistake of trying to use the lowest f stop and alot of the time its not needed. Did you try using a higher F stop say 5.6?
Thanks for the reply. But I want the subjects in focus and a really blurred background. That’s why I want to use 1.8
 
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Rick
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#4
Thanks for the reply. But I want the subjects in focus and a really blurred background. That’s why I want to use 1.8
Unless they are all the same distance from you (focal plane) then you won't be able to do that. At 1.8, you will have a shallow depth of field, especially if using a telephoto lens, less narrow with a more wide angle. By choosing a larger F stop number, and therefore smaller aperture, your depth of field will increase.

Pick the focus point on the area you want to be sharp, anything on that focal plane will be sharp, but you can't focus in more than one focal plane at once, regardless how many points you choose.

If some shots were blurred, it could be your shutter speed was too slow, and you had either camera shake, or subject movement.
 
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Ian
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#5
Depth of field depends on aperture, focal length and distance to subject. Only knowing 1 of those isn't much help. But if you plug that information into this site, you can see how much depth of field you had and work out whether you were making things difficult for yourself. As an example, 50mm on a crop sensor at f1.8 & subject distance of 2m = 10cm depth of field (1.95m - 2.05m) which is quite shallow. However if they were at 4m, the depth of field jumps to 40cm (3.8 - 4.2m) which is much more forgiving

It sounds to me like you were in a big rush if you're not even sure the half press was working! Blur can be cause by missed focus, subject movement and photographer movement so it's not necessarily missed focus to blame. Could be one of, or a combination of, many things.
 
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Dougie
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#7
I have a sigma 18-35mm 1.8 lens


And the subjects will be about 1-3 meters from me
f1.8 ain't going to work for that.

Have the subjects as far as you can from the background and test from 2.8 upwards.
 
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6,711
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#10
Thanks for the reply. But I want the subjects in focus and a really blurred background. That’s why I want to use 1.8
As has been pointed out, you need to control the subjects positioning and the choice of aperture to ensure that all of them are within the focus zone covered by the DoF for that focal length for the distance from camera and distance from the background.

To simple state what you want to have, as you have discovered is not always possible..........................as Scotty said to Jim, "I canna do it Captain, it defies the laws of physics................"

Run your own tests to prove it to yourself :)
 
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22,401
Name
Phil
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#11
Half my pictures were in focus and half weren’t

And I don’t know why!

Maybe because I was snapping too quick and not half pressing the shutter?
Try back button focussing, relax and be one with the camera. Play with your camera constantly till using it is 2nd nature, like driving.

When shooting a single model what AF point setting should I use?
Whichever is most suitable, once your technique is solid, it’ll be unimportant.

Also, when shooting a group of people, say 3 people stood next to each other. How do I get them all in focus but using an F stop of 1.8.

Which AF point should I use?
You’ll need them stood in exactly the same plane, otherwise a higher f stop to give you enough DoF, check a DoF calculator, keep the subject to bg as large as you can.

I don’t use manual. Not really learnt yet.

I use AV
Unimportant, but it is important to understand when your camera meter will get it wrong, use exp lock or exp comp, then you’ll know when shooting in M makes more sense (sometimes but not often)

Last weekend I went out shooting for the first time. I shot some friends in their new clothing brand.
I’m sorry I can’t comment without asking why you took on what sounds like a ‘job’ when you’re clearly not ready.
 
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Jamesev
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#14
Depth of field depends on aperture, focal length and distance to subject. Only knowing 1 of those isn't much help. But if you plug that information into this site, you can see how much depth of field you had and work out whether you were making things difficult for yourself. As an example, 50mm on a crop sensor at f1.8 & subject distance of 2m = 10cm depth of field (1.95m - 2.05m) which is quite shallow. However if they were at 4m, the depth of field jumps to 40cm (3.8 - 4.2m) which is much more forgiving

It sounds to me like you were in a big rush if you're not even sure the half press was working! Blur can be cause by missed focus, subject movement and photographer movement so it's not necessarily missed focus to blame. Could be one of, or a combination of, many things.
Or use f4. Just because you have a f1.8 lens doesn't mean you're limited to F1.8. Dial in F4 at the same settings and the DOF increases to 25 cm. Still enough to blur the infront of and behind of (if whats behind is about 1 m behind.
 
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willkia
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124
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Will
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#15
I’m sorry I can’t comment without asking why you took on what sounds like a ‘job’ when you’re clearly not ready.
I was just helping some friends out. Free of charge. They were really happy with all the pics that were in focus.

I was just annoyed with the ones that were out of focus and didn’t know why
 
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Shaun
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#16
I was just helping some friends out. Free of charge. They were really happy with all the pics that were in focus.

I was just annoyed with the ones that were out of focus and didn’t know why
Putting a few of the OOF shots up might help, one problem could potentially be that, if you we're using the auto focus point selection that it was picking the wrong point to focus on.
I never use AF point selection in auto mode for this reason
 
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willkia
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124
Name
Will
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#17
Putting a few of the OOF shots up might help, one problem could potentially be that, if you we're using the auto focus point selection that it was picking the wrong point to focus on.
I never use AF point selection in auto mode for this reason

Which setting do you reccomend I use?
 
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22,401
Name
Phil
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#19
I was just helping some friends out. Free of charge. They were really happy with all the pics that were in focus.

I was just annoyed with the ones that were out of focus and didn’t know why
Then read the rest of my post. ;)

Asking what others do won’t help, finding what works for you is the only way. There’s no shortcuts, it just takes practice.
 
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22,401
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Phil
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#21
I was just helping some friends out. Free of charge. They were really happy with all the pics that were in focus.

I was just annoyed with the ones that were out of focus and didn’t know why
I’m honestly not having a personal dig, this is about the state of the industry, not about you and your mates.

Off course they were ‘happy’, they got free pictures, and have no concept of how much better the images would have been if they’d paid for a pro to produce them.

And if they have the same attitude to marketing generally, they’ll never realise why their business didn’t do 10x better.
 
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