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depth of field question
I recently got a new DSLR (K10D) the learning process has been a lot of fun..

I've seen some beautiful shots in some of the forums. I understand the basics of DOF, but how do you get the foreground and background of a subject blurry with the subject in the middle in focus. large aperture is what I understand, but when I try it, I either get the foreground or background blurry, but not both?.

I hope this does not seem like a stupid question..

Thanks in advance...

Comments (8)

Things you can do to achieve a shallow depth of field:.

1. Shoot wide open and adjust exposure with the shutter speed2. Use a long focal length3. Use manual focus..

Comment #1

Amit Bidaye wrote:.

I recently got a new DSLR (K10D) the learning process has been a lotof fun..

I've seen some beautiful shots in some of the forums. I understandthe basics of DOF, but how do you get the foreground and backgroundof a subject blurry with the subject in the middle in focus. largeaperture is what I understand, but when I try it, I either get theforeground or background blurry, but not both?.

With the Sigma 18-50 mm, at f/2.8 and at the long end (50 mm) you should easily be able to get both OOF, providing they are some distance from the subject..

Do you have any shots to post?.

Brian A...

Comment #2

You might want to look at this site. It will provide you with a DOF calculator. After you play with it for a while you will have a very good understanding of potential camera settings and distance..

Http://www.dofmaster.com/dofjs.html.

MaddogOlympus E-500, Olympus E-510..

Comment #3

Amit Bidaye wrote:.

I recently got a new DSLR (K10D) the learning process has been a lotof fun..

I've seen some beautiful shots in some of the forums. I understandthe basics of DOF, but how do you get the foreground and backgroundof a subject blurry with the subject in the middle in focus. largeaperture is what I understand, but when I try it, I either get theforeground or background blurry, but not both?.

I hope this does not seem like a stupid question..

Thanks in advance..

Yes, use a long or somewhat telephoto lens. Yes, use a wide-open or at least fairly large lens opening (small f-stop like 1.7 to 3.5)..

Then remember that wherever you focus, that about 1/3 of your DOF is in front of that point and 2/3 of that DOF is behind. Keep it simple.ngk20000..

Comment #4

Amit Bidaye wrote:.

I recently got a new DSLR (K10D) the learning process has been a lotof fun..

I've seen some beautiful shots in some of the forums. I understandthe basics of DOF, but how do you get the foreground and backgroundof a subject blurry with the subject in the middle in focus. largeaperture is what I understand, but when I try it, I either get theforeground or background blurry, but not both?.

Probably (!) you have too much DOF. Get closer to the subject..

I hope this does not seem like a stupid question..

Nope..

Usually DOF is thinner in front of the focus plane than behind it. Use that .

/d/n..

Comment #5

Ngk20000 wrote:.

Then remember that wherever you focus, that about 1/3 of your DOF isin front of that point and 2/3 of that DOF is behind. Keep it simple..

This is an 'urban myth', or whatever the photography of equivalent of that would be called. I don't know the origin of it, but I have always imagined it to be an old beginner's photography book which was taken on faith by it's readers who then passed it on without question. A couple of examples follow. Sensor size affects depth of field calculations so these are for the K10D that the OP asked about:.

50 mm lens, f/5.6, at 1 metre (a fairly tight portrait where depth of field can be critical). Depth of field extends about 4 cm in front of the focus point and 4 cm behind, or more accurately 48% in front and 52% behind - i.e. very nearly equal..

21 mm lens, f/5.6, focused at 4 metres. Depth of field extends about 2 metres in front, and to infinity behind. That is to say, if you want everything in acceptable focus from 2m to (let's say) 1 km, do you focus at 334 metres as the 'rule' would suggest? No - focus at just 4 metres, because almost all the depth of field is behind..

I used http://www.dofmaster.com/dofjs.html for the calculations..

This doesn't actually answer the original question, which is about what is out of focus rather than how much is in, but I just wanted to debunk that myth - not for the first time, and not for the last I am sure!..

Comment #6

Amit Bidaye wrote:.

I recently got a new DSLR (K10D) the learning process has been a lotof fun..

I've seen some beautiful shots in some of the forums. I understandthe basics of DOF, but how do you get the foreground and backgroundof a subject blurry with the subject in the middle in focus. largeaperture is what I understand, but when I try it, I either get theforeground or background blurry, but not both?.

It's a combination of things. All these affect the amount of blur:.

- Focus point (usually this is the camera to subject distance)- Foreground distance- Background distance- Focal length- Aperture.

You need to balance all of these, and it is not necessarily obvious how to do that. The depth of field, referred to by other posters, does have a bearing on this but it is just one factor. Another is that longer lenses, assuming the same subject framing, produce more background blur. And another is that the amount of background blur has a limit determined by the focal length and the aperture, whereas the foreground blur has effectively no limit..

You are doing the right thing - keep on experimenting. But use these pointers:.

- If you can't get enough background blur, even with a distant background, you must use a longer lens and/or a larger aperture..

- If you can't get enough foreground blur, change the camera-foreground-subject distances so the the foreground is proportionately closer to the camera..

Hope that helps!.

((Edit: DoF calculators have been mentioned, but a blur calculator is more directly relevant to your problem. Try this one:.

Http://www.bobatkins.com/.../photography/technical/bokeh_background_blur.html.

It's a bit technical perhaps, but it will allow you to calculate all the relationships I have mentioned and get *exactly* the same foreground and background blur, if that is what you want.)).

I hope this does not seem like a stupid question..

No!..

Comment #7

Thanks so much for replying guys, this clears up a lot.....

I'm going to experiment with it a little more, especially at the longer end of my 18-50 mm and see how it goes..

Overall, I have to say, I'm loving my K10D...

Comment #8

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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