Photoforum Photography Challenge 2011-14 - Narrow Depth of Field & Bokeh

[arian29]

bokehhhhhhh.......
hope you like it..

DSC_1279.jpg

[TCampbell]

Beautiful examples!

[BRAINY]

@SONYNUT, I love it! Simply love it
@arian nice shot too ^.^ Do you like your D3100? I almost bought it!

[arian29]

Yes the 3100 is good. i like it a lot. am a beginner and it is just perfect for me

[jovymontoya2005]

Wow!..its beautiful and unique.

[paddlehiker]

OK, another bokeh attempt. f/4.5, 1s, at 32mm. Subject was 10' from camera, tree about 18'. Probably could have increased bokeh by moving camera and subject back another 10' but was running out of room.
IMG_2950 (Large).jpg

[hotelfm]

Nice bokeh balls But yeah try to move the camera back. The front is also a bit out of focus.



Professionel fotograf i hele Danmark

[TCampbell]

There are two factors that control how much bokeh you'll get.

The first, and most obvious, is the aperture opening on the lens (the focal ratio or f-stop). The lower the f-stop (which means the lens has a larger clear aperture), the larger and more obvious defocusing will occur on those areas which are out of focus. Basically the lens is focused to some subject distance and at that precise distance everything will focus to a point. Anything closer or farther from that distance will be out of focus and each point defocuses in a circular shape (which they refer to as the "circle of confusion"). Technically every out-of-focus point defocuses into a circular pattern (the actual pattern matches the shape of the opening in the lens - which is usually designed to be round, hence the circle. But if your lens has say, 5 aperture blades, then you might see a pentagonal shaped blur.)

The reason I waited until the holidays to spring this particular challenge is because any pinpoint of light will defocus into a soft round spot of light (the "circle of confusion" -- except it's REALLY obvious when the defocused object is a tiny lightbulb.) It makes for very beautiful background bokeh subject and this is the time of year where you can holiday lights just about everywhere -- even if you don't decorate with them yourself, chances are you'll find them all around town.)

The second, and less obvious factor, is the focal length of the lens. The size of the defused circles ("circles of confusion") is relative to the magnification in the image. When you use a very wide angle lens, things are not magnified -- in fact you could say they are negatively magnified (seem farther away in the photo then they do in real life). Hence any blurring is hard to notice. When you do the opposite... and zoom in quite a lot (long focal length lens) then everything in the image is magnified, including the blur.

If you combine these two factors, it means that the way to get the very strongest bokeh is to use a very "long" lens with a very large aperture opening. I have a 135mm f/2.0 and also a 300mm f/2.8 lens that both produce amazing bokeh (neither of which were used when I posted my example photo because I shot this in my living room where neither lens would have been practical.)

On most 'kit' lenses or on point & shoot cameras with non-removable lenses, the focal ratio usually varies... the best (lowest) focal ratio is available only at the widest angle. As you zoom in the focal ratio increases. That limits how much bokeh you can create because you can't use the combination of the widest aperture at the longest focal length. Some zoom lenses can maintain a constant focal ratio even as you zoom, but of course those lenses are more expensive. That's why I suggested that if you happened to own the inexpensive 50mm lens for your camera (the "nifty fifty"), this would be the time to use that lens (f/1.8 focal ratio makes this easy.) It's a very inexpensive lens, with a great focal ratio, and very good image quality -- it's the one lens that probably most people can afford (hence the nickname "nifty fifty"). Pretty much every major consumer camera maker has one... Canon, Nikon, Sony, Olympus, etc. and they all sell in the $100-125 range. It's generally always the least-expensively priced lens in the entire lineup.

I try to think up challenges that can be done with any camera, but there are a few really good challenges that might require the right equipment to pull off. Since the ability to have a tack-sharp subject with a beautifully de-focused background is one of the key goals for a lot of photography (it helps in "subject isolation" -- where only the subject is in focus and all the distractions of the background are blurred), I didn't want to leave this challenge out even though some cameras would not be able to do it very well.

Even if your camera and/or lens aren't ideal for doing it, at least now you know what the effect is and know how it's created.

[paddlehiker]

Thank you hotelfm for your kind reply and I agree the foreground isn't as sharp as it could be. And Tim, thanks for your explanations of DOF, aperture, focal length, and bokeh. This challenge was a great learning experience!