Depth of Field with aperture settings?

Canon 12x IS USM (S3 IS built-in Lens) -- 36-432mm (35mm EQ)

04/13/2009 12:26:52 PM · #1

For some reason I'm not seeing how changing the aperture would change the depth of field. I think I need an explanation on "depth of field" first of all, and then an explanation on using the aperture to change the depth of field. Please help.

delin

Canon EOS-40D

04/13/2009 12:29:46 PM · #2

This helped me a lot-

//www.dpchallenge.com/tutorial.php?TUTORIAL_ID=1

GeneralE

Canon PowerShot S3 IS

04/13/2009 12:29:51 PM · #3

The "explanation" requies some real physics/optics. The "guideline" is that the larger the aperture, the shallower the DOF.

tpbremer

Nikon D80

Nikon AF Zoom-Nikkor 18-135mm f/3.5- 5.6G ED DX

04/13/2009 12:33:02 PM · #4

If you want an explanation that will probably blow your mind and perhaps confuse you more check wikipedias explanation. It shows how complex the optics are, but has some simple info that can help.

Put your camera into Aperture priority mode. Open up your aperture completely and focus on a person or subject say 3 feet away. Then close your aperture down all the way and take the same shot. compare. Doing this with a yardstick and a table with objects placed nearer and further from the lens can also demonstrate it.

Canon EF 100-400mm f/4.5-5.6L IS

04/13/2009 12:40:43 PM · #5

depth of field - could be called depth of field of focus

basically the amount of the captured image that is visibly in sharp focus.

the shallower the depth of field ( lower the aperture number setting ) - the less is in focus. an example of shallow depth of field

a higher aperture number setting value generally gives deeper depth of field ( more of the image is in sharp focus ). an example of deep depth of field.

Message edited by author 2009-04-13 12:41:38.

Strikeslip

Canon EOS-5D

04/13/2009 12:49:34 PM · #6

.... aaaaand ....

The f number is really the reciprocal. Sooooo, f3 is 1/3 is bigger than f8 is 1/8. ;-D

04/13/2009 12:50:35 PM · #7

Awesome information! Thanks a lot! Can't wait to get home from work and practice!

Lutchenko

Sigma 24-70mm f/2.8 EX DG Macro for Nikon

04/13/2009 12:51:20 PM · #8

[quote=JLSmith] For some reason I'm not seeing how changing the aperture would change the depth of field. I think I need an explanation on "depth of field" first of all, and then an explanation on using the aperture to change the depth of field. Please help. [/quote]

I notice that you have a couple of macro shots on your profile so it may be worth mentioning that when you are very close to the subject that you
are photographing, changing your F number will have little affect on your depth of field and maybe this is why you can't see why you are not noticing
a DOF change.

There are lots of DOF calculators you can get that will tell you what your DOF will be for any given lens/F nos/distance from subject.

Yo_Spiff

Olympus OM-D E-M5 Mark III

Olympus 12-100mm f/4.0 M.Zuiko ED IS PRO

04/13/2009 12:57:50 PM · #9

Here are a couple of examples I did with the same scene. Note that these examples were taken with a compact camera, a Powershot S5. An SLR would have more blur due to the physics of larger sensor size and longer focal length.

At F4.0, the fence is in focus, but the building is blurry

At F8.0, both are in focus

04/13/2009 01:09:25 PM · #10

So just to make sure I understand what I have read...
If i had a higher aperture setting on

...
Then more of the tulips would be in focus?
And with a lower aperture, closer tulips will be clearer while the farther back tulips become more out of focus?

Sony 24-70mm F4 Vario-Tessar T* FE OSS

04/13/2009 01:12:25 PM · #11

the depth field will corespond with what YOU focus on.

it's not really how close the subject is to the camera that drives what is in focus... ( though that does affect DOF ).

other than that you are correct.

in that photo you posted - my guess would be the upper left hand tulip was TOO close for the camera to focus on at any aperture. if you know what i am getting at ... ?

Message edited by author 2009-04-13 13:13:43.

Bear_Music

Samsung Galaxy S24 Ultra

04/13/2009 01:13:13 PM · #12

And, just for the record, DOF is a function of the physical size of the aperture, NOT the "f/stop". Little, tiny holes = deep DOF, big, wide holes = shallow DOF. F/stop, by definition, it the ratio of the diameter of the aperture to the focal length of the lens. So a 25mm aperture on a 100mm lens is f/4. Same aperture on 200mm is f/8. Same aperture on 400 mm is f/16. But the DOF stays the same across the 3 lenses, assuming each lens is focused to the same distance. In other words, 100mm, f4 DOF = 200mm, f/8 DOF = 400mm, f/16 DOF....

R.

Canon RF 24-70mm f/2.8 L IS

04/13/2009 01:15:17 PM · #13

and just for the record - how many times have you posted that same info :)

not to knock the question poster in any way shape or form. just having fun...

i had posted similar info in my original post - but it was too simplified and i edited it out...

Originally posted by Bear_Music:

And, just for the record, DOF is a function of the physical size of the aperture, NOT the "f/stop". Little, tiny holes = deep DOF, big, wide holes = shallow DOF. F/stop, by definition, it the ratio of the diameter of the aperture to the focal length of the lens. So a 25mm aperture on a 100mm lens is f/4. Same aperture on 200mm is f/8. Same aperture on 400 mm is f/16. But the DOF stays the same across the 3 lenses, assuming each lens is focused to the same distance. In other words, 100mm, f4 DOF = 200mm, f/8 DOF = 400mm, f/16 DOF....

R.

Message edited by author 2009-04-13 13:16:35.

kirbic

Canon EOS R5

04/13/2009 01:16:07 PM · #14

Originally posted by JLSmith:

So just to make sure I understand what I have read...
If i had a higher aperture setting on...
Then more of the tulips would be in focus?
And with a lower aperture, closer tulips will be clearer while the farther back tulips become more out of focus?

First part is correct. Second part, not so. Your point of best focus will still be the same with a narrow aperture, but stuff nearer and farther becomes more blurred as you increase aperture (decrease f number).

Bear_Music

Samsung Galaxy S24 Ultra

Sony 24-70mm F4 Vario-Tessar T* FE OSS

04/13/2009 01:16:19 PM · #15

Originally posted by JLSmith:

So just to make sure I understand what I have read...
If i had a higher aperture setting on ...
Then more of the tulips would be in focus?
And with a lower aperture, closer tulips will be clearer while the farther back tulips become more out of focus?

Roughly speaking, for a given amount of DOF, 1/3 of it is in front of the point of focus and 2/3 behind the point of focus. So if you have a 12-inch ruler inclined away from the camera that you want entirely in focus, first focus on the 4-inch mark then stop down the lens sufficiently to get the desired DOF. As a rule of thumb, you want to focus 1/3 of the way into a scene where maximizing DOF is an issue.

R.

Lutchenko

Sigma 24-70mm f/2.8 EX DG Macro for Nikon

04/13/2009 01:18:26 PM · #16

If you wish to understand why things appear in and out of focus as a result of aperture size, focal distance etc etc then this link gives an
excellent breakdown.

wikipedia DOF

04/13/2009 01:21:41 PM · #17

and that would be getting into the hyperfocal distance discussion - which can be calculated - correct ? infinity focus so to speak.

it's easier with a wide angle lens. harder with a long focal length lens ( unless it's a macro lens ).

a 1/3 of the way into a given scene is going to be much farther away with a 200mm lens than it is with a 12mm lens.

Originally posted by Bear_Music:

As a rule of thumb, you want to focus 1/3 of the way into a scene where maximizing DOF is an issue.

kenskid

Nikon AF-S NIKKOR 24-70mm f/2.8G ED

04/13/2009 01:22:28 PM · #18

Squint your eyes when looking at something far off and tell us what happens!

04/13/2009 01:28:57 PM · #19

it gets blurry cuz i'm looking through my eyelashes :)

04/13/2009 01:29:28 PM · #20

Originally posted by kenskid:

Squint your eyes when looking at something far off and tell us what happens!

Ka-ching! It's all clear now!

Lutchenko

Sigma 24-70mm f/2.8 EX DG Macro for Nikon

04/13/2009 01:31:31 PM · #21

Originally posted by kenskid:
Squint your eyes when looking at something far off and tell us what happens!

I went all dizzy and started seeing dots.... is this sensor dust lol

kenskid

Nikon AF-S NIKKOR 24-70mm f/2.8G ED

04/13/2009 10:17:02 PM · #22

LOL...yes it is dust !

However, Squinting eyes is EXACTLY what aperture is to a lens.

Originally posted by Lutchenko:

Originally posted by kenskid:
Squint your eyes when looking at something far off and tell us what happens!

I went all dizzy and started seeing dots.... is this sensor dust lol

BrennanOB

Canon EOS-1D Mark II

Tamron SP AF 28-75mm f/2.8 XR Di for Canon

04/13/2009 10:30:48 PM · #23

My fave way of explaining the relationship between the f/stop number and the size of the aperture is that the number is the number of the size of the hole it takes to cover the (full frame) sensor. At f/2 the hole is big enough that two circles covers the sensor. At f/64 it takes 64 of those tiny holes to cover the sensor.

kenskid