Depth of field

alexthecheese

alexthecheese

alexthecheese

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I bought a Canon Powershot S80 the otehr day and have since beenr eading techniques on how to get the most out of it, and came across a technique which you guys call Depth of Field and I have no clue about what it is.

Well, I think I sorta do actually - that fantastic photo a few threads down with the dew on the leaf is a DOF photo is it not? If it is I was just wondering how to go about doing it, and also would my camera be able to do it?

Also are there any good guides that I can get my teeth into for using my camera? DPReview has some good ones but I've soaked those up already :)
 
Yeah the picture has a shallow depth of field, so the background is out of focus and so blurred when the subject is in focus. A quick google returns this which explains it quite well. Basicly when you focus on the subject in the foreground, a larger apeture gives a shallower DOF, and anything more than a certain distance will be out of focus(generally the background, but when using macros with a very shallow DOF, parts of the subject can also become out of focus)
 
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www.photo.net can explain everything you need to get on track!

In short & sweet, DoF is the background and foreground blur and the intensity of it, it could be shallow or it could be deep.

A shallow DOF would be like this:
2.jpg

(f/2.8)


Whilst a deeper DOF would be like this:
1.jpg

(f/22)

You can control the dof by adjusting the aperture on your camera/lens. A large aperture is a smaller f number and vice versa. A large aperture gives you the best DOF and can be used to excellent creative effect as is seen on this forum a lot whilst you would want a smaller aperure for shooting a landscape to get everything in detail and sharp.

having a smaller aperture means a longer exposure time is needed though because more light is needed to hit the sensor.

On a DSLR a large aperture does show it's downside in certain conditons on EVERY lens by EVERY brand, these can be anything from vignetting to chromatic abberations and edge sharpness loss and others.

It's up to you to find these downsides at the aperture range of your lens or camera so you know when it will be performing its best in each situation :)
 
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Thanks for the replies, I thought it was something like that but had never even heard of an aperture setting before!

Thanks also for the link, I'll get reading on that tomorrow.

One other thing though, is that with the Canon camera that I have on order, will it be possible to actually distinguish the depth of view from the LCD screen whilst lining up the shot? Obviously the viewfinder wont take into account the aperture setting, meaning that I'll have to rely on judging the shot from the LCD which sounds like it could be tricky.
 
alexthecheese said:
Oh and that's ET on your desk, isnt it. :p
Click to expand...
et_1.jpg


:p

I've not used the compact digis with manual aperture control but others here have so should be able to tell you!
 
As far as I know, it won't be possible to use the LCD to do that, as I believe when you're framing an image the apeture is fully open, and only changes size when actualy taking the picture, which is why some cameras have a DOF preview, so if yours does you'll be able to (i don't think it does, in which case, just do it by trial and error)
 
The actual F-stop is applied only once you take the photo (or in the case of DSLRs, when you press the DoF Preview button so that the aperture is mechanically adjusted) - otherwise, I think it would mess up the metering and focus when it stops down at any time other than actually taking the shot.

I found that it's really difficult to get a good DoF blur on compacts apart from macro modes or using the very longest end of the telephoto, due to the very short actual focal lengths of the lenses on compacts.
 
Evil-Penguin said:
As far as I know, it won't be possible to use the LCD to do that, as I believe when you're framing an image the apeture is fully open, and only changes size when actualy taking the picture, which is why some cameras have a DOF preview, so if yours does you'll be able to (i don't think it does, in which case, just do it by trial and error)
Click to expand...
Unless your lens is fully manual then you set the aperture blades up and that will close the aperture via the aperture ring.
 
Right, ok. To be honest from what I've read now it sounds the effect I was hoping for won't be as profound with a compact camera, but I did notice you can change the aperture which DPReview.com quoted as below:

• Wide: F2.8 / 3.2 / 3.5 / 4.0 / 4.5 / 5.0 / 5.6 / 6.3 / 7.1 / 8.0
• Tele: F5.3 / 5.6 / 6.3 / 7.1 / 8.0
 
alexthecheese said:
Right, ok. To be honest from what I've read now it sounds the effect I was hoping for won't be as profound with a compact camera, but I did notice you can change the aperture which DPReview.com quoted as below:

• Wide: F2.8 / 3.2 / 3.5 / 4.0 / 4.5 / 5.0 / 5.6 / 6.3 / 7.1 / 8.0
• Tele: F5.3 / 5.6 / 6.3 / 7.1 / 8.0
Click to expand...

The problem with Compact Digital camera is their sensors are really tiny and a small sensor means a larger depth of field, even at F2.8.

It will still be possible to achieve an out of focus background at F2.8 but you will need to be close to your subject with the background far way.
It won't work with general portraits.
 
SDK^ said:
The problem with Compact Digital camera is their sensors are really tiny and a small sensor means a larger depth of field, even at F2.8.

It will still be possible to achieve an out of focus background at F2.8 but you will need to be close to your subject with the background far way.
It won't work with general portraits.
Click to expand...

Does that mean, something like a 5D, with a full frame sensor has a narrower depth of field than a 1.6x crop? Suppose it must do..
 
No the DOF on a full frame camera would be deeper wouldn't it because there is no crop factor :? - or am I missunderstanding something?

A 1.5x body at 100mm would be 150mm so you would get 50mm more dof from a portrait whereas with fullframe you lose that extra 50mm and get 100mm so to get the same dof you need to be moving closer to the subject.

Any SLR based camera has deep or shallow dof on any prime or midzoom lens.
 
mrk said:
No the DOF on a full frame camera would be deeper wouldn't it because there is no crop factor :? - or am I missunderstanding something?
Click to expand...

Yes, you are misunderstanding something :)

See the image below

Nikon D2X on the left (1.5x crop) , Canon 1Ds MKII on the right (full 35mm)

Both taken at F5.6

DOF-compare-f5.6.jpg


DOF is inversely proportional to format size.
Note that format size is inversely proportional to the "digital multiplier". The higher the "digital multiplier", the smaller the format and thus the greater the depth of field.

With an 8x10 camera you have about 8.5 times LESS depth of field than you do with 35mm for the same image. This also explains why consumer digicams, some of which have sensors 1/6 the size of 35mm film, have such a large depth of field and one of the reasons why it's almost impossible to get blurred backgrounds when using them.
 
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