Dof


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zOOm

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#1
Old topic but I need revision :D

what actually determines amounting of background blurring? (or selective focusing???). I always thought opening up aperture will do just that, but I have seem f6.3 that blurred the background as much as me @ f2.8

anyone care to explain the science of DOF in greater depth??
Or perhaps direct me to a good website for furthur reading?? :)

Thanks a zillion!
 

ziploc

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#2
Things that affect DOF:
1. Aperture size (its diameter) - lower f-number => bigger aperture => lesser DOF (more background blur).
2. Focal length - longer focal length (telephoto) => lesser DOF.
3. Lens to subject distance - shorter distance => lesser DOF.

If you want to blur out the background, you need to find a background that is far away from your subject too.

See this page and this page on the Nikon website for the factors affecting the DOF and the explainations.
 

#3
How does the DOF preview button work? I thot you'll be able to see areas of sharpness and blurness, but looking through the viewfinder, everything looks equally dark and blur. :dunno:
 

Mudpool

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#4
Originally posted by rubric
How does the DOF preview button work? I thot you'll be able to see areas of sharpness and blurness, but looking through the viewfinder, everything looks equally dark and blur. :dunno:
Me => newbie, I have your problem oso but unintentionally saw the effect last night while doing some close-ups. Try doing a close-up of something. Then while having the DOF button pressed, do a manual focus of the object. Do that again in other f numbers and you'll see the difference. A 50mm can do the job already, I wonder how much DOF can a 100mm produce :p

Maybe the distance between the subject and the film affects DOF more than aperture, that's why we can't see it in normal shots. :dunno:
 

ziploc

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#5
Originally posted by rubric
How does the DOF preview button work? I thot you'll be able to see areas of sharpness and blurness, but looking through the viewfinder, everything looks equally dark and blur. :dunno:
The area that is at (or near) the "plane of sharpest focus" will be clear, where as the other areas will be blur... how blur depends on how far are they from that plane and the DOF. The reason why it becomes dark is because when you press the DOF preview button, the camera actually releases the aperture down to the set f-stop value. The aperture is normally kept at the widest to facilitate for focusing (either auto or manual) and metering.

Try to focus on a near subject, vary the aperture value and then press the DOF preview to see the effect. :)
 

ziploc

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#6
Originally posted by Mudpool


Me => newbie, I have your problem oso but unintentionally saw the effect last night while doing some close-ups. Try doing a close-up of something. Then while having the DOF button pressed, do a manual focus of the object. Do that again in other f numbers and you'll see the difference. A 50mm can do the job already, I wonder how much DOF can a 100mm produce :p

Maybe the distance between the subject and the film affects DOF more than aperture, that's why we can't see it in normal shots. :dunno:
Hi Mudpool,

For normal, non macro shooting, you can find out the DOF from the DOF table provided in the instruction flyer that came with your lens. :)
 

zOOm

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#7
Originally posted by ziploc
Things that affect DOF:
1. Aperture size (its diameter) - lower f-number => bigger aperture => lesser DOF (more background blur).
2. Focal length - longer focal length (telephoto) => lesser DOF.
3. Lens to subject distance - shorter distance => lesser DOF.

If you want to blur out the background, you need to find a background that is far away from your subject too.

ziploc,
wow! thanks for the nikon link. it got the basic of photography all inside. need something to digest all those stufs.
 

siron

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#8
To make thing simpler...

It would means that DOF yes depend on Aperture,

BUT...if you say zoom x5 optical or x10 optical zoom...and ur subject is far from the back grd...I suppose even at f6 etc will still get you a blur background.

Thus distance plays a big part in dof...
 

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