Bokeh with T4i

weird question since I don't know what I'm doing wrong

how can I ensure a blurred background ? Sometimes w same lens and settings the background will blur and sometimes it doesn't.  How can I guarantee blur?

can you post a couple such pics?

chances are they have very different apertures or the same aperture but at very different distances.  a faster aperture keeps less of the distance in focus, a smaller one keeps more in focus.  i believe that to have everything in focus, you'd need an aperture of f/16 or a little better whereas an aperture of f/1.8 will only have a little bit of the pic in focus - it'll give much more bokeh, but if you shoot a face, for example, maybe only the nose will be in focus.

Crotonmark wrote:

OK Please see the two images below - both have same aperture

well, similar aperture (f/5.6 v f/5)

But very different focal lengths, 300mm v. 135mm. f/5.6 with 300mm will give much narrower depth of field and more background blur than f/5 with 135mm.

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

thanks

Crotonmark wrote:

Thanks again but there is no bokeh in the 135mm shot.

Be close to your subject.  Be far from the background.

R2

Crotonmark wrote:

Thanks again but there is no bokeh in the 135mm shot.

FYI. Bokeh isn't blurred background, it's the quality of the out of focus areas.

Crotonmark wrote:

jvceac wrote:

Crotonmark wrote:

Thanks again but there is no bokeh in the 135mm shot.

FYI. Bokeh isn't blurred background, it's the quality of the out of focus areas.

Can you explain this more please

I'm not the best person to clearly explain this but I'll give it a shot. Most lenses can give you a blurred background. Bokeh describes the quality of that blurring. If you've seen pictures with blurred lights in the background you can see that the rings those blurred lights produce vary in harshness and shape from 1 leans to another. Some of that is determined by how many blades the lens has, some by the quality of the glass. I'm sure there are other variables as well.

Your original question has nothing to do with the quality of the blurred background (bokeh), just depth of field (front to back area that is in sharp focus). Your 1st picture that has more background blur had the subject close to the lens with a lot of separation between subject and background. in the 2nd picture, the subject was far away from the lens and the distance between the subject and background was minimal.

There are others who frequent these forums who know far more about this than I do so if I've mangled the explanation, please jump in.

Crotonmark wrote:

weird question since I don't know what I'm doing wrong

how can I ensure a blurred background ? Sometimes w same lens and settings the background will blur and sometimes it doesn't. How can I guarantee blur?

Pretty much almost any lens on your T4i can make a blurred background.

For more "bokeh" do the following:

1. Use a smaller aperture

2. Use a longer focal length

3. Come closer to the subject

4. Move the subject farther from the background

5. Pay attention to background lighting

And another one that doesn't know what" bokeh" means.

jvceac wrote:

And another one that doesn't know what" bokeh" means.

https://en.wikipedia.org/wiki/Bokeh

That's right, so you can't get "more bokeh" only better or worse bokeh.

Yes, isolation or shallow depth of field.