DOF - how to?


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coldman

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May 12, 2004
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#1
Hi Pro,

How do you guys/gals get the blur blur background, sharp sharp foreground photo?
what setting to use?
i tried using f2.8 but stil very difficult to get.
must i get those dslr (they got dof button) then i can control the dof?

Thanks in advance.
 

Astin

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#2
You can try to move your main subject further away from the background, ie main subject nearer to your camera. But you must set the camera auto focus to the main subject.
 

justarius

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#3
How much DOF you get is dependent upon 3 things: focal length, aperture, and distance from subject.

The longer the focal length, the less DOF you have.
The larger the aperture, the less DOF you have.
The closer you are to the subject, the less DOF you have.

So to get a picture with background blur and foreground sharp, use a longer lens at a large aperture while ensuring the background is far away from your main subject. :D
 

nightwolf75

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Dec 18, 2003
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#4
justarius said:
How much DOF you get is dependent upon 3 things: focal length, aperture, and distance from subject.

The longer the focal length, the less DOF you have.
The larger the aperture, the less DOF you have.
The closer you are to the subject, the less DOF you have.

So to get a picture with background blur and foreground sharp, use a longer lens at a large aperture while ensuring the background is far away from your main subject. :D
try reading up here! very helpful article. :thumbsup:

http://luminous-landscape.com/tutorials/understanding-series/dof.shtml
 

Snowcrash

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#5
justarius said:
How much DOF you get is dependent upon 3 things: focal length, aperture, and distance from subject.

The longer the focal length, the less DOF you have.
The larger the aperture, the less DOF you have.
The closer you are to the subject, the less DOF you have.

So to get a picture with background blur and foreground sharp, use a longer lens at a large aperture while ensuring the background is far away from your main subject. :D
and also on the size of your CCD/CMOS
 

LanEvo7

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Aug 13, 2004
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#6
coldman said:
Hi Pro,

How do you guys/gals get the blur blur background, sharp sharp foreground photo?
what setting to use?
i tried using f2.8 but stil very difficult to get.
must i get those dslr (they got dof button) then i can control the dof?

Thanks in advance.
Saw u using Pana FZ10, f/2.8 at telephoto > 300mm should be produce a good background blur, if still not enough, PS CS it.

- Select your subject (magnetic lasso + fine tuning using lasso)
- Save selection as channel
- Select the channel u just save an apply gaussian blur for 1 pixel
- Select back the image and apply Lens blur using the channel u saved just now as mask.
- Voila!
 

Newman

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#7
Snowcrash said:
and also on the size of your CCD/CMOS
Not directly though. The size of the CCD/CMOS affects the focal length of the lens which can be used, which in turns affects the DOF.
 

roygoh

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#8
Newman said:
Not directly though. The size of the CCD/CMOS affects the focal length of the lens which can be used, which in turns affects the DOF.

Actually quite directly....the size of the sensor versus the size of the final output affects the circle of confusion, which is in turn a direct factor determining the DOF, besides the focal length, aperture and subject distance.
 

Newman

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#9
roygoh said:
Actually quite directly....the size of the sensor versus the size of the final output affects the circle of confusion, which is in turn a direct factor determining the DOF, besides the focal length, aperture and subject distance.
Sorry Roy, I'm a bit confused here. As quoted from Michael Reichmann:
'There was a query in October, 2001 on my Discussion Forum as to whether Depth of Field was calculated any differently for digital Vs. film. The answer is, no. There is no difference whosesoever. DOF doesn't care about the recording media type or size, though a lower COF is used for medium and large format, since the amount of magnification to make a decent sized print is much less than for 35mm.'
Isn't the CCD/CMOS the recording media? :dunno:

Or maybe I belong to the COF as jokingly defined by Michael:
'Definition: "A group of photographers sitting around trying to understand Depth of Field". '
:bsmilie: :bsmilie: :bsmilie:
 

roygoh

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#10
Newman said:
Sorry Roy, I'm a bit confused here. As quoted from Michael Reichmann:
'There was a query in October, 2001 on my Discussion Forum as to whether Depth of Field was calculated any differently for digital Vs. film. The answer is, no. There is no difference whosesoever. DOF doesn't care about the recording media type or size, though a lower COF is used for medium and large format, since the amount of magnification to make a decent sized print is much less than for 35mm.'
Isn't the CCD/CMOS the recording media? :dunno:

Or maybe I belong to the COF as jokingly defined by Michael:
'Definition: "A group of photographers sitting around trying to understand Depth of Field". '
:bsmilie: :bsmilie: :bsmilie:

Your quote is correct, the DOF calculation remains the same regardless of the medium. What goes into the DOF equation are focal length, subject distance, aperture and COC, and the euqation does not care about the type of medium (film, CCD or CMOS).

COC is affected by the sensor size and the magnification from sensor size to final output (screen or print size), as pointed out by the second half of your quote from Michael Reichmann. For the same sized print, COC_film is larger than COC_CCD (since most CCDs are smaller than film) to achieve the same DOF with everything alse being the same. As such the sensor size affects DOF directly, not just affecting the choice of focal length.

Of course when you factor in the effect of CCD size on the choise of focal length (to achieve the same angle/field of view) the impact of sensor size is reduced, however, the net effect is that smaller sensor size actually results in higher DOF as compared to film if field of view, aperture and subject distance are kept constant. That's why the "blur background" effect is less on a digicam compared to a DSLR even if the equivalent focal length and aperture are the same.

I was responding to your statement that sensor size does not affect DOF directly.

:)
 

sulhan

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#11
coldman said:
Hi Pro,

How do you guys/gals get the blur blur background, sharp sharp foreground photo?
what setting to use?
i tried using f2.8 but stil very difficult to get.
must i get those dslr (they got dof button) then i can control the dof?

Thanks in advance.
The distance B should be greater than the distance A + try the longest focal length (better if the camera minimum focus distance is very short)



rgds,
sulhan
 

yanyewkay

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Sep 22, 2004
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#12
Actually for beginners like me, I normally set my camera zoom to half of the maximum to achieve some longer focal length and go round shooting pics.

I just have to stand a further from my target.

Try using this program from DOF Master . It is a disc/calculator some sort which does the same thing for the dSLR's lens like the one below


Picture taken from DOF Master.

Best thing it's FREE. :bsmilie:

Just input your camera's COC (can be found on the website itself) and focal length range.

Print out and assembly the discs and walla!
It's quite a useful tool to have around for beginners. :D

Else if you bring a palm around there also the Palm OS version.

After some time I sort of gotten the hang of acheiving my DOF without the disc. :D

Hope it helps
 

ssoulm

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#14
This is very helpful for newbies like me :cool: Keep the tips coming.... :bsmilie:
 

Newman

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#15
roygoh said:
Your quote is correct, the DOF calculation remains the same regardless of the medium. What goes into the DOF equation are focal length, subject distance, aperture and COC, and the euqation does not care about the type of medium (film, CCD or CMOS).

COC is affected by the sensor size and the magnification from sensor size to final output (screen or print size), as pointed out by the second half of your quote from Michael Reichmann. For the same sized print, COC_film is larger than COC_CCD (since most CCDs are smaller than film) to achieve the same DOF with everything alse being the same. As such the sensor size affects DOF directly, not just affecting the choice of focal length.

Of course when you factor in the effect of CCD size on the choise of focal length (to achieve the same angle/field of view) the impact of sensor size is reduced, however, the net effect is that smaller sensor size actually results in higher DOF as compared to film if field of view, aperture and subject distance are kept constant. That's why the "blur background" effect is less on a digicam compared to a DSLR even if the equivalent focal length and aperture are the same.

I was responding to your statement that sensor size does not affect DOF directly.

:)
Thanks Roy for your explanation. My mind is still not taking it in yet. Perhaps it's because my mind is still 'recovering' from ICT syndrome :D . Just finished today and I'll come back to this after my head is clear.

Cheers!
 

justarius

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#17
dfbread said:
hi folks ..

so armed with a Canon A80, is it possible to do DOF ? or at least .. a simple DOF ? thanks :)
I don't think you do DOF. What is a complicated or simple DOF? DOF is simply the area of sharpness in your picture.
 

yanyewkay

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Sep 22, 2004
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#18
hahah whether it is "simple" or "complicated" DOF it is possible with the A80 although it is slightly harder because the manual focusing is only from 0.5 -5m then infinity (not too user friendly but still good to have some form of manual focusing).

-Using only optical zoom, set to full telephoto (or whatever focal length)
-use a relative big aperture (f2.8 or 3.2) for limited DOF
-if you know the distance to the object then it'll be good to use manual focus otherwise you have to try to autofocus on the object correctly.

example:
at full telephoto (with f2.8) and you are standing 3m away from your object, only things that fall between 2.8m and 3.3m remains relatively sharp. All others will start to become blur. Probably you can focus at 2.8 to enhance the blur background effect.

but if you set to full wideangle (with f2.8)at 3m, the range now becomes 1.6m - 18m. So you'll have to focus further (2m maybe) to get that "blur background" effect.

Because you're not focusing AT the object but slightly in front of it all the time.. your intended object may not be at it's best sharpness...

The above is valid only for the A80 because different cameras have different COC and range of focal lengths. There are many online DOF calculators to find the above info.

There is also a mathematical equation to get the above values.. but that's another story.. :D
 

dfbread

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Sep 19, 2004
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#19
yanyewkay said:
hahah whether it is "simple" or "complicated" DOF it is possible with the A80 although it is slightly harder because the manual focusing is only from 0.5 -5m then infinity (not too user friendly but still good to have some form of manual focusing).

-Using only optical zoom, set to full telephoto (or whatever focal length)
-use a relative big aperture (f2.8 or 3.2) for limited DOF
-if you know the distance to the object then it'll be good to use manual focus otherwise you have to try to autofocus on the object correctly.

example:
at full telephoto (with f2.8) and you are standing 3m away from your object, only things that fall between 2.8m and 3.3m remains relatively sharp. All others will start to become blur. Probably you can focus at 2.8 to enhance the blur background effect.

but if you set to full wideangle (with f2.8)at 3m, the range now becomes 1.6m - 18m. So you'll have to focus further (2m maybe) to get that "blur background" effect.

Because you're not focusing AT the object but slightly in front of it all the time.. your intended object may not be at it's best sharpness...

The above is valid only for the A80 because different cameras have different COC and range of focal lengths. There are many online DOF calculators to find the above info.

There is also a mathematical equation to get the above values.. but that's another story.. :D
thanks thanks yanyewkay... though it needs time to digest :)
 

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