DOF Help

ccsnet

ccsnet

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Name
Terran
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I know what it is.... I think I know how to get it but so far had poor results imho.

DOF is the relationship of the size of the aperture vs the speed of the shots and ( I think as this where it gets a bit duff ) a quick shot and large apperture gives me a shot DOF - every thing in the back ground is fuzzy....

So - problem is this - I have a 450d.... I've been playing with both the manual and AV features yet every time I try I seem to just get a clear photo ( yes I'm using MF ).

I've tried using 1/125 5.6 iirc and a variations with what to me seems little effect. I've tried using the DOF preview button and then the adjuster wheel with the shutter button half down but to me it just goes slightly darker and I cant see any changes..... now this may be my expectation here but I'm pretty sure it should preview here and not just the final shot on the LCD....

I'd really apprciate some tips from you guys been a SLR noob.

TIA

Terran
 
DOF is related to the apperture setting & not really the shutter speed. You correctly say that large apperture (small F no) gives a shallow depth of field. It is best to have your subject as far away as possible from the background you intend to blur out, & it also helps if you zoom your lens fully. You should be able to see the effect on the lcd screen, but will be better viewed on your pc monitor etc.

hth
 
The way i always think of it is a low f number f1.8 gives a small area of the image in focus with everything else blurry, a high f number f22 makes everything in the image in focus

Not very technical I know but it helps me:lol:
 
you're not going to blur a windmill unless you're within several metres of it (small windmill...?) unless you had literally a 100mm f/0.1 lens... some things just aren't to be. besides, what is there to blur really in the sky?
 
trencheel303 said:
you're not going to blur a windmill unless you're within several metres of it (small windmill...?) unless you had literally a 100mm f/0.1 lens... some things just aren't to be. besides, what is there to blur really in the sky?
Click to expand...
This is what I'm thinking.... been new to SLR I'm still playing with what I can and cant do.... re closeness.... yes just a few meters from it using a 55-250.... its actually not that big really, about 3 stories high.

Terran
 
hmm in that case you might manage it. zoom in a fair bit and use maximum aperture. you aren't going to get a fantastic amount of blur though - if any at all - and like i said before what is there in the sky to blur?
 
trencheel303 said:
hmm in that case you might manage it. zoom in a fair bit and use maximum aperture. you aren't going to get a fantastic amount of blur though - if any at all - and like i said before what is there in the sky to blur?
Click to expand...
You do have a point.... still experince imho....:D

I'll get there eventually and thats half the fun imho....

Terran
 
agree that is a fantastic website, that doggie must be famous by now!

looks suspiciously like the skateboarding dog on youtube :thinking:
 
If you want to put some numbers on it, this is the place www.dofmaster.com

Two things affect depth of field - f/number, and magnification (image size). You've got the f/number bit, but on magnification the smaller the subject is in the frame, the more depth of field you have, and vice versa.

So move closer, or fit a longer lens, and DoF gets less (you can't change this on that interactive site). Just to get a feel for it, when you're right up close, your DoF will be measured in inches, at middle distance it will be a few feet, and further away it will be yards.

There comes a point (depending on focal length) where everything is sharp beyond a certain distance - that's infinity. With your windmill, you're probably approaching infinity so very little scope to create shallow DoF.
 
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