DOF help

Bolerus · 7 Feb 2007 at 16:48

this is such a newbie question I know.

But can somebody remind me how to get a shallow DOF.

is it high Aperature or low Aperature

I have been playing with a couple of settings and it doesent seem to change.

OR am i just going insane

FranchiseJuan · 7 Feb 2007 at 16:49

It is a low apiture number (the smaller the number the better), and usually helps if you are trying to focus on something closer to you rather then further away.

Fireskull · 7 Feb 2007 at 16:58

Quick question for people who know about DOF, is it the high DOF that makes lights seem like sparkles? and the low that makes them a blurr?

Johnny|lucidcomposure · 7 Feb 2007 at 17:00

Range

F1.2 = Such a fine line of focus for the depth of field (very shallow)
F2.8 = Shallow depth of field mainly used for macro and isolation of a single item
F4 = Some background blur but not enough to really shout about
F8 = again slight background blurryness
F11 = trying to achieve a lot in focus here
F16 = Urban landscape shots sorta depth of field (Everything appears in focus)
F22 = The landscape setting for achieving best full depth of field. (again, everything in focus)

Bolerus · 7 Feb 2007 at 17:02

thanks guys.

for some reason i had got it into my head it was the higher number the lower the depth of field, I had takes the Aperature up to 32 lol. pic was a bit dark, but all in focus

FranchiseJuan · 7 Feb 2007 at 17:03

Fireskull said:
Quick question for people who know about DOF, is it the high DOF that makes lights seem like sparkles? and the low that makes them a blurr?

It is a shallow DOF that makes the lights seem like sparkles, but the apearence of out of focus lights depends on the lens design, and if you want almost perfect circles, then you need a lens with a 7/8 apiture blade design.

themask70 · 7 Feb 2007 at 17:34

Fstop11 said:
Range

F1.2 = Such a fine line of focus for the depth of field (very shallow)
F2.8 = Shallow depth of field mainly used for macro and isolation of a single item
F4 = Some background blur but not enough to really shout about
F8 = again slight background blurryness
F11 = trying to achieve a lot in focus here
F16 = Urban landscape shots sorta depth of field (Everything appears in focus)
F22 = The landscape setting for achieving best full depth of field. (again, everything in focus)

Heed his advice lol. Very good definition of it.

SDK^ · 7 Feb 2007 at 17:47

Don't forget defraction

In each case this is the maximum F-stop to get the full resolution of the camera. It is perfectly OK to stop the lens down further than this, but know that when you do, you will be getting less than the full resolution. This may or may not matter.

Canon 5D : F9
Canon 1Ds: F9
Canon 1Ds Mark II : F8
Nikon D2X : F5.6
Canon 20D : F7.1
Canon G7 : F2

So, for example, if you take a Canon EOS 1Ds Mark II and stop it down to F9, you are going to get greater depth of field, but you will not get the full 16 million pixel resolution – instead you'll get resolution more like a 5D or 1Ds. When I know that I want to make a very large print, I stay at or below the maximum f-stop for diffraction limited resolution.

In the case of the Canon G7 it is diffraction limited at F2. Yet the minimum aperture on the camera is F2.8. What this means is that the camera NEVER can deliver its full stated 10 megapixel resolution. Diffraction will limit it to less than this. The 10 megapixel sensor is thus more of a marketing slogan than reality. It suggests that if Canon wants to come out with a G8 camera, then there is no point in going beyond 10 megapixels – they’d better either upgrade the lens, or admit that diffraction limits the resolution to less than what the sensor is producing.

^^Gord^^ · 7 Feb 2007 at 21:30

Now that is an interesting post SDK^!

What is the math behind it?

Johnny|lucidcomposure · 7 Feb 2007 at 21:45

I swear I have learnt everything technical I know from SDK. I think he is a Canon Rep secrectly.

SDK^ · 7 Feb 2007 at 21:48

It's quite complicated to explain.
This is a long read and a bit hard to grasp but worth going though it :http://luminous-landscape.com/essays/Equivalent-Lenses.shtml

Blackvault · 7 Feb 2007 at 22:17

SDK^ said:
Don't forget defraction

In each case this is the maximum F-stop to get the full resolution of the camera. It is perfectly OK to stop the lens down further than this, but know that when you do, you will be getting less than the full resolution. This may or may not matter.

Canon 5D : F9
Canon 1Ds: F9
Canon 1Ds Mark II : F8
Nikon D2X : F5.6
Canon 20D : F7.1
Canon G7 : F2

So, for example, if you take a Canon EOS 1Ds Mark II and stop it down to F9, you are going to get greater depth of field, but you will not get the full 16 million pixel resolution – instead you'll get resolution more like a 5D or 1Ds. When I know that I want to make a very large print, I stay at or below the maximum f-stop for diffraction limited resolution.

In the case of the Canon G7 it is diffraction limited at F2. Yet the minimum aperture on the camera is F2.8. What this means is that the camera NEVER can deliver its full stated 10 megapixel resolution. Diffraction will limit it to less than this. The 10 megapixel sensor is thus more of a marketing slogan than reality. It suggests that if Canon wants to come out with a G8 camera, then there is no point in going beyond 10 megapixels – they’d better either upgrade the lens, or admit that diffraction limits the resolution to less than what the sensor is producing.

That's an interesting post but I'm confused and my brain hurts. Does that mean with my 30D to be about to achieve 8.2mp I have to shoot between F/1.0-F7.1?

Blackvault