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What is a sweet spot and is Bokeh and sweet spot are same?

ZiaZia Member
edited June 2012 in general photography
I'm using canon.
What is the sweet?
Is bokeh same as sweet spot?
How can you know if it's a sweet spot?
How do you create one?
I'm using the following equipment.
Camera: Canon 60D
Lenses: Sigma 30mm f/1.4, Canon 50mm f/1.4, Canon 100mm f/2

Thanks in advance

Comments

  • TrevTrev Moderator
    Zia,

    The 'Sweet Spot' is often referred to the best resolution of a lens at a certain aperture.

    In the past before lenses became so more effective than a few years back, a lens with a say wide open aperture, often performed better if 'stopped' down, generally in the 1+ range, so it was probably better performing at say f4 or f5.6 than at f2.8 if that was the widest aperture.

    It's not often these days where a good quality lens is required to have this done, unless one of the cheaper kit lenses whereby the aperture is not a 'constant' one.

    Eg: say a 18-200mm lens will have a range of maybe f3.5-f5.6 where when zoomed out at the wider end will be able to get f3.5, but when zoomed in you would only be able to open to f5.6, instead of f3.5

    Bokeh, that is entirely different. It refers to the quality of a lens' performance at wide open aperture and how smooth the background is at that wide aperture.

    It has nothing to do with shallow depth of field, not the same even though many people refer to having a nice shallow depth of field. Good quality lenses always outperform less stellar ones, even if they have the same zoom, and the same f-stop.

    The Bokeh is a Japanese term 'boke' which means "blur" or "haze"; and therefore meaning the way the lens renders out-of-focus points of light. There is 'good' and 'bad' bokeh.

    Differences in some lens' aberrations and aperture shape cause those lens designs to blur the image in a way that is pleasing to the eye, while others produce blurring that is unpleasant or distracting and plain downright ugly.

    Are the out-of-focus pints of light smooth and uniform, or are they some other shape and texture? Smooth, uniform, aesthetically pleasing blur is "good" Bokeh while blur which shows evidence of ugly shape and structure is "bad" Bokeh.

    You cannot 'create' a sweet spot. But you can simply test the lens at a wide aperture, see if it's nice and sharp across the board or fuzzy/not quite sharp. If so, step it down to the next f-stop. eg: Your Sigma 1.4, test that at 1.4, then step it down to say f4 or f5.6, see which is the better. If even at all apertures, great, but more than likely it won't be, not a 1/3rd party lens like the Sigma. It will probably perform better at f4+.

    Actually I just found Neil's blog perfectly explaining:
    http://neilvn.com/tangents/2009/01/10/bokeh-the-quality-of-blur/

    Hope this helps.

    Trev.
  • regarding sweet spots, a sweet spot is like trev said "best resolution of a lens at a certain aperture." for instance if u shoot with ur 50 1.4 at f1.4 the in focus area of resulting photo will not be as sharp as if u stopped it down to f4 especially on the edges of the frame
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