Bokeh ! Aperture or Focal length

Paul11

Paul11

Paul11

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am i right that both aperture and focal length would effect the bokeh

of the two options (at a given distance)

which would be prefrered for more bokeh.

wider aperture F2.8 . instead of F4

or 105mm instead of 70mm ?
 
Paul11 said:
am i right that both aperture and focal length would effect the bokeh
Click to expand...

They do yes, but another factor is also your distance from the subject vs the background,

eg: if the subject is very close to a 300mm F2.8, and the background is a good distance away - the whole thing will just be blown away into smooth bokeh, but the closer the background to the subject - the less bokeh.

Paul11 said:
of the two options (at a given distance)

which would be prefrered for more bokeh.

wider aperture F2.8 . instead of F4

or 105mm instead of 70mm ?
Click to expand...


70mm @ F4 will give you the least bokeh, 105mm @ 2.8 with give you the most, I guess from that you can roughly work out what you need,
 
if i understood the dof calculator the 105 @ f4 would give thinner DOF , therefore more bokeh (based on 10ft distance)
 
It's correct that you have less depth of field with 104mm @ f/4, all other things being equal

But that's not really the only factor because..
At a longer focal length you will step back to get the same framing, which will increase your depth of field
At a longer focal length, the background is also enlarged so (I might be wrong about this one) you get larger circles of confusion
At a wider focal length at the same distance you will frame your subject differently which will increase the amount of background in the shot, which may have an impact on perceived bokehness.
If that is the widest aperture of each lens, you may find in practice the lens doesn't have the quality you want wide open so you may not ever actually use that aperture in the real world.

In practice the maths can be a nightmare to get your head around and it's easier to find examples and see how they compare.
Try the advanced search at http://www.pixel-peeper.com/ and you can narrow down by focal length and aperture.

My personal experience is that when using a longer lens I tend to look for situations where there is a large distance between the subject and the background. The compression combined with the magnified background tend to really increase the apparent level of bokeh without requiring a very wide aperture - but that probably applies more to longer focal lengths than that..
When using a wider lens I am taking different kind of pictures.. although the difference between 70 and 104 is not that great relatively
 
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ok, the real question is ..

would a 24-70 F2.8 give a nicer photo / bokeh / seperation than a 24-105 F4

for shooting parties/events.
 
Paul11 said:
my bank balance to going to cry.......
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If you can find a mk1, i'd get one of those. I do not believe the mkii is twice as good.

This is a small thing but I think mk1 has a better design with the zoom/hood. Mk1 the lens extends within the hood, which gives it protection even if you knock it. Mk2 the lens extend with the hood so knocking it means the gears is going to take a bit of a beating.

If you are buying new though, Mk2 is stellar.
 
Another option is the Tamron 24-70 VC - the VC is invaluable and the optics are sharper, brighter and better corrected than the original Canon 24-70. It's only if you need the build of the Canon that I'd suggest it at this point unless you over-value the red ring or need to stay within Canon for CPS. In the light of Sigma's recent form, Tamron's turnaround has been somewhat overlooked but their 24-70 is an absolutely fantastic bit of kit.
 
Raymond, THC_SsSsSnake was referring to your Forum Avatar rather than the lady in your signature - hence to him you are slightly overweight black guy in a hat!
 
Also, Bokeh does not equal DoF. Bokeh refers to the quality of out of focusing rendering.

Faster apertures give you shallower DoF but that doesn't have any effect on the Bokeh.
Funnily enough Bokeh quality is often better on slower aperture (and loner) lenses. Bokeh quality can also be negatively affected by the corrective elements to reduce aberrations and improve sharpness. Some of the best lenses for Bokeh are older lens that are noticeably soft and lack contrast wide open


Bokeh quality is also massively effected by the background. Harsh highlights can cause stronger ringing and more nervousness.
 
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