How to focus objects at difference distances?

[duarted]

Hello,

This might be basic but I don't know the answer to it.

So I have 3 objects here, at different distances from the camera. How can I focus all of them in the same photo? I'm using a Canon 6D + Canon 50mm 1.8 and I can only focus one of the objects.

What should I do to focus the 3 objects?

Thanks!

 

[Ysarex]

Lenses only focus on flat planes. So the simple answer is you can't. If your camera lens is focused on something that is 1.3 meters away from you then it is not in focus on something that is 1.2 meters away or 1.4 meters away. That you can't change. What you can change is the degree of blur or "out of focus" that's visibly apparent both in front and behind the plane of focus. You do this by using a smaller aperture or iris in the lens. The phenomenon is called depth of field (DOF) and you can go here to learn about it: Hyperfocal Distance and Depth of Field Calculator - DOFMaster

Joe

 

[Derrel]

You could try stopping the lens down, to f/16 or f/22, which would give deeper depth of field. Also, at f/16 or f/22, you could move the focus placement around a bit, to get the best possible compromise, with the most in acceptable focus.

If you realllllllly want to "pull focus" on all three items, a Canon tilt/shift lens would be helpful here, by allowing you to mechanically "tilt" the lens forward a bit to use the Scheimpflug principle. Same thing with a Zorki lens adapter that would allow you to swing the lens to the left, and re-align the depth of field plane along an angled line that hits the right side of all those three objects.

Focus-stacking, with multiple shots, merged at the computer, is the new way of achieving deep DOF on subjects like this.\

Your example photo shows how a "fixed camera" has some limitations. A fixed camera meaning a camera that can not move the lens (or the rear film plane) in order to re-position the depth of field plane in any way. In an earlier era, using a camera that has "movements", the desired effect you would like could be achieved in-camera. The desired effect could be done with a view camera, but we don;t use those kinds of cameras much these days.

 

[duarted]

Hmm okay I get it.

So why is it that I can focus the three objects with a phone camera for example?

Thanks!

 

[astroNikon]

Aperture - Depth of Field
In General, The bigger the sensor the more shallow the depth of field
So a small camera sensor has a large depth of field.
there's a thread around here about that .... looking

you'll have to read through all the other stuff but here's a few
==> Depth of field: Full-frame lens vs. APS-C lens, both on APS-C sensor | Page 2 | Photography Forum

==> Are cell phones as good as DSLRs? My friend says 'yes'. | Photography Forum

 

[sashbar]

Hmm okay I get it.

So why is it that I can focus the three objects with a phone camera for example?

Thanks!

A phone camera has a tiny sensor compared to a DSLR camera. The smaller the sensor the deeper is the depth of field with the same aperture. That is why you can not control your DoF with a phone camera - almost everything is always in focus.

 

[Derrel]

The small-sized sensor in a smartphone camera needs only a very short lens, and short focal length lenses achieve hyperfocal focus at very close focused distances. When a lens is focused at its hyperfocal focusing distance on its own appropriately-sized sensor, the depth of field extends from close, to Infinity.

With the iPhone or Android smartphone cameras, a lens in the 3 to 4 mm focal length range is what is needed, more or less. A teeny little lens like that, on a teeny little sensor, allows the user to shoot from close to far with "hyperfocal focus", which is sometimes also called "pan focus". Both of those terms mean basically, "The maximum depth of field this lens/sensor/film size can achieve."

The deep inherent depth of field of a smartphone camera is one thing that makes them so great at making snapshots on the go!!! i LOVE my iPhone's camera!!! I use it as a camera probably 200x more than as a phone, seriously, by actual picture count vs calls!!

 

[TCampbell]

"Depth of Field" is the range of distances at which objects will appear to be more-or-less in acceptable focus. If you focus on a subject 5' away and have VERY SHALLOW depth of field, then elements which are merely a few inches nearer or farther will already appear blurred. But if you have VERY BROAD depth of field then objects even several feet closer or farther will appear to be reasonably well focused.

Three main factors control the depth of field.

1) The size of the lens aperture. Smaller apertures increase the depth of field. Larger apertures reduce it. A pin-hole camera has a very very tiny aperture and doesn't technically even have a lens... it's just a hole. And yet everything seems to be somewhat focused because the hole is so very tiny.

On a DSLR camera you can control the size of the aperture. This gives you the ability to have tack-sharp focus on your intended subject and deliberately blur the background... drawing attention to your subject. You can't do that with a camera phone. But you can also use a very tiny aperture (e.g. f/22 for example) and have very broad depth of field.

2) The focal length of the lens. Wide angle lenses naturally have very broad depth of field... at any f-stop. Long focal lengths naturally have shallower depth of field... sometimes even at high f-stops. I have a 14mm ultra-wide lens and at that focal length the depth of field is so broad I can pretty much just focus the lens manually to about 3' and the whole world is in focus (almost).

3) Subject distance. If your subject is very close you naturally get shallower depth of field. Distant subjects have broad depth of field. This actually creates a bit of a challenge for macro / close-up photographers because it's difficult to focus extremely close objects and have a broad depth of field.

 

[FArrival]

Yup, the only thing you can do is drop the f-stop as much as you can, and focus on the middle object so that the distance between the other two is shortest. Other than that there's not much you can do, unless you step away as much as possible, shoot, and then crop (which still may not achieve the desired result).

 

[greybeard]

Stop it down to f/16 and focus on the pencil glass. The larger the sensor, the shallower the depth of field (depth of focus) will be for any given f/stop. Your phone has a really tiny sensor so it has a much deeper DOF than your dSLR.

 

[duarted]

Ok I understand now. Thank you everybody for the help!