You have to have enough of a distance differential between the subject and the background to get good bokeh. The link is a great tool for understanding depth of field. LOL.
Http://www.dofmaster.com/dofjs.html.
Ron.
D4018-5555-200VR50mm f1.8SB400..
The amount of 'blur' you get in the background depends on a number of things. Anyone, please feel free to add to this if I leave anything out. The aperture is certainly very important. While 3.5 can give you good bokeh, lenses with lower wider apertures like 2.8 or 1.8 will give you even more. The distance from your subject to the background also plays a significant role. The further away the background is the easy it will be to get it to be out of focus.
If you have a 70-200 zoom, you will get a shallower DOF at 200mm ( and therfor more 'bokeh') than you will at 70mm..
Here's a recent shot I took with a 18-200mm zoom. The aperture was even narrower than the 3.6 you mention ( it was 5.6) but it still shows decent bokeh because the background is far away and the zoom was at 98mm..
Image control:Zoom outZoom 100%Zoom inExpand AllOpen in new window.
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Mike.
Http://www.liquidartgallery.com.
'For every complex problem there is a solution that is obvious, simple..and wrong'..
I have Pentax K10D and Tamron 28-75 f/2.8 lens .
~S...
Thanks for helping me so in general it's about aperture, focal range and distance between subject and background so if I will have 70-200 with f/2.8 on f/2.8 at 200mm I will get very good bokeh ok, it's clear to me .
~S...
WildSammy wrote:.
Thanks for helping me so in general it's about aperture, focalrange and distance between subject and background so if I willhave 70-200 with f/2.8 on f/2.8 at 200mm I will get very good bokeh ok, it's clear to me .
Not necessarily. If your 70-200 stays at f/2.8 at 200mm, then you surely will get a shallow depth of field but your bokeh (I take this to mean "the appearance of out-of-focus objects") could still be bad, depending on how your lens is corrected at 200mm..
Leonard Migliore..
See how you get on with your current lens..
At the long (75mm) end of the zoom and f/2.8, you should find you get a fairly limited depth of field, if your subject is relatively close..
Give that a go before worrying about 70-200 zooms...
I was going to add that. Basically, Bokeh is the quality of the out of focus elements, not the quantity or degree of focus..
While focal length, aperture value and subject to background distance are factors, the shape of the aperture is also important in creating pleasing bokeh. In general, a lens with more and rounded aperture blades gives better bokeh than a lens with fewer and straight blades. Pretty much all of the lenses known for great bokeh have nine blades which are rounded..
The quality of a lenses boken is most easily judged in how it renders point light sources in the background. If a point light source is rendered as a smooth solid disk, it's considered pretty good. If the point light source shows obvious sides (5-7 blades) or as a ring then bokeh is said to be harsh.Chefziggyhttp://www.pbase.com/chefziggy/lecream..