DoF Question

[vivaldibaby]

Can someone explain to me how to create a shallow depth of field?
I keep thinking that I've gotten it right - then I don't.

Thank you!! :p

[Mike]

You need to have your lens set to a wide aperture and then focus on your subject. The nearer you are to your subject the narrower your depth of field will be. Put your camera into Av mode and set it as wide as it will go - f/2.8 - f/5.6 depending on your lens.

Look here for dof calculator: http://www.dofmaster.com/dofjs.html

[sandpiper]

The main things that affect DoF are:

Wide aperture: The bigger the aperture (smaller number) the shallower the DoF.

Distance to subject: The nearer you are, the shallower the DoF.

Focal length: The longer the FL of the lens, the shallower the DoF.

Sensor size: The bigger the sensor, the shallower the DoF.


So, a long lens, used wide open close to the subject and on a FF DSLR like a 5D / 1Ds will give lovely shallow DoF.

You don't say what sort of camera you are using, if you are using a point & shoot rather than a DSLR, that could explain why you are not succeeding (you say that you think you have got it right ...). The small sensor size and short focal lengths are great for snapshots as the large DoF means that most stuff is in focus, but make deliberate shallow DoF work almost impossible to get great results with.

[vivaldibaby]

You don't say what sort of camera you are using, if you are using a point & shoot rather than a DSLR, that could explain why you are not succeeding (you say that you think you have got it right ...). The small sensor size and short focal lengths are great for snapshots as the large DoF means that most stuff is in focus, but make deliberate shallow DoF work almost impossible to get great results with.

I'm using a Rebel XT with the 17-85 lens..
So I think your suggestion (and Mike's!) will be helpful....

[Wilt]

All the above is true. What few people understand is that you combine factors and they nullify each other!

For example. 50mm f/4 focused on subject from 20' away had DOF zone of 17.4-23.3', or 6.2' deep

Change to a 100mm f/4 lens and move back to 40' from subject to keep them constant size in the frame, and you get DOF zone of 37.1-43.3', or 6.2' deep

So while 'longer LF is less DOF' that is a generalization that does NOT always prove out!

[Hermeto]

The main things that affect DoF are:

Wide aperture: The bigger the aperture (smaller number) the shallower the DoF.

Distance to subject: The nearer you are, the shallower the DoF.

Focal length: The longer the FL of the lens, the shallower the DoF.

Sensor size: The bigger the sensor, the shallower the DoF.


So, a long lens, used wide open close to the subject and on a FF DSLR like a 5D / 1Ds will give lovely shallow DoF.

You don't say what sort of camera you are using, if you are using a point & shoot rather than a DSLR, that could explain why you are not succeeding (you say that you think you have got it right ...). The small sensor size and short focal lengths are great for snapshots as the large DoF means that most stuff is in focus, but make deliberate shallow DoF work almost impossible to get great results with.

Bolded part is not true.

http://photography-on-the.net/forum/showpost.php?p=6741071&postcount=33

http://photography-on-the.net/forum/showthread.php?t=603520

[sandpiper]

Bolded part is not true.



If you take the same shot (i.e. identical framing and composition) with each format, the shot taken on FF has much shallower DoF than that taken on crop.

I agree that much of that is due to using a longer FL, of course. But the fact remains that taking identically framed and composed shots on a FF and a cropper will show much shallower DoF on the FF shot. So, regardless of why that occurs, if you want to take a specific shot the FF will have shallower DoF.

I know that I can get great shallow DoF with my 5D (FF) and can't get it taking the same shot on my 20D (crop). Equally, my 20D gets used for all the macro work as the 5D struggles to get sufficient DoF.

When I shoot stuff for ebay I have to use my point and shoot (tiny sensor) because neither DSLR can remotely approach the DoF I need for that. Regardless of that being due (in the main) to using different FLs to gain the same framing, I can only use that FL to get that much (or little) DoF using the appropriate sensor size. Hence, in practical terms, you get much shallower DoF when using a larger sensor.

It's no good saying that the FF won't affect the DoF, because if you use a longer lens on the cropper (from the same position) or move forward (with the same FL) you will gain the same DoF. By doing that you will also lose a large part of your subject out of the frame. So sensor size affects DoF by allowing you to use a longer lens or stand nearer. Arguing that it's the FL that changes the DoF is pedantic because you can only use that FL because you are shooting FF.

Sensor size does still affect DoF directly though, due to the cropper shot having to be enlarged much further to give a specific sized print, the circles of confusion will also be enlarged.

[JeffreyG]

Bolded part is not true.


In a tetchy, strictly worded way it might not be true. If you shoot FF and 1.6X at the same focus distance, aperture and focal length then yes, the FF camera will yield more DOF. But nobody in the world shoots the two formats that way.

As most people comprehend things, they want to compare two cameras used to take the same picture. This generall means equal perspective (same position) but a longer focal length on the FF camera to achieve the same angle of view. Once you do this, the FF camera gives much shallower DOF at a given aperture.

Bothering with the first case is (IMO) pointless and just confuses people who are trying to understand the differences.

[Hermeto]

Whatever rocks your boats, guys.
You can have it any color you like, as long as it’s black.. ;)

[tonylong]

The good news is that the OP only has the one body, and we don't need to confuse things (and each other) with the whole sensor size/DOF discussion:)!