When is there "too much bokeh"?

[jerryph]

Never! :D :D

Bokeh, sometimes referred to as background blur (but can be foreground, background or even both at the same time), is a function of having a lens with a large aperture. Some lenses have a large aperture like an F/4, F/2.8 or even bigger, like a really big F/1.8 aperture.

When you get into lens that are in the F/1.4 class, that's when a ton of really interesting things start to happen. DOF (depth of field) is drastically reduced, but if you understand how DOF works, a lens with an aperture of F/1.8 or less becomes a boon in low light conditions, and/or is a bokeh junkie's best friend (lol).

Since my 85mm F/1.4 Nikkor lens came in and I started playing with it, there were a few things that came out for me.

First, these lenses can take properly exposed pictures in environments that would leave other lenses giving you motion blurred collages of smudges instead of clean, crisp pics.

Second, you LEARN about shallow DOF in new ways that you never thought possible before. Nuances of how to blur come fast, because at these apertures, the DOF is razor thin. How thin you ask? Let me give you an example:


http://farm4.static.flickr.com/3168/2966992885_8f2591fc2d.jpg

In the (not too impressive) picture above, you see a metric ruler. I took the picture trying to be as close to 45 degrees as possible with the focus being on the 7.5cm mark and took the shoot.

I was close to the minimum focus distance of the lens and hand held this shot in a poorly lit room. As you can tell, the 7 and the 8 are in focus, and everything else is clearly blurred. With the angle that I was at, this means that I had a depth of field of way under ONE HALF A CENTIMETER! Anything that was 1 cm in front of or behind the point of focus was blurred. Period.

Imagine if you had taken a breath after focusing? It would mean that your subject could easily be off and therefore the picture unnecessarily wasted. Great care has to be taken focusing these lenses at apertures of F/2.8 and greater, they are very, very sensitive.

Oh, the above picture was not taken at F/1.4 like some may have thought, but at F/1.8. Had I take the picture at F/1.4, the DOF would have been even more razor thin!

It also means that I have the ability to hand hold a camera and take clear motion blur-free pictures of someone holding a candle in a dark room (a future project that I am dying to play with soon :) ).

After my bokeh jones was more or less satisfied, I then started to notice some other things about this lens of mine... the the much reduced need to sharpen the pics in post process, the richer colours and clearer "contrasty" look that characterized it compared to my other lenses. It was quite expensive, but now that I've had a chance to play with it, I am glad that I went with this lens instead of the F/1.8 variant.

A couple of pictures from this lens:


http://farm4.static.flickr.com/3242/2967089571_c66160a355.jpg

http://farm4.static.flickr.com/3047/2967936004_acbb69da9a.jpg

http://farm4.static.flickr.com/3004/2967936170_19f1b1c47e.jpg

http://farm4.static.flickr.com/3167/2967934906_c6d2d18e53.jpg

http://farm4.static.flickr.com/3032/2967936110_0cff018aa3.jpg

[reval8r]

Thanks for sharing this post Jerry. I think it will really help our fellow students here.

Fast lenses are really great for low light situations, but my eyes have gotten so bad the past few years, I'm afraid to even try a lens faster than 2.8. I also tend to shoot in the 5.6 to 11 range to keep my images from being out of focus.

The issues you discussed with the depth of field with fast lenses also apply to macro photography. With macro changes less than a cm puts the image out of focus even at apatures of around f8. For those that are into really close-up macro, they use special sliding mounts on a tripod that allow for focus changes down to mm.

[jerryph]

Most definately, David... a hair's width is the difference in a well blurred or sharply focused picture in any macro mode, even with very small apertures below F/8.

As I am sure you know, in the non-macro world large apertures cause a shallow DOF, however, unlike the macro world, where we cannot do anything about it due to the very nature of macro pictures, to increase DOF without changing apertures, all we do is increase the distance between us and the subject (As you recall, amount of bokeh is defined in the ratio between the distance from your camera to your subject vs the distance from the subject to the area behind it).

Which basically means that if I was 5 feet away from a face with a candle, at F/1.4, the DOF would be shallow and it would be challenging to get the candle and face both in focus. However, stepping back to about 12-15 feet and without changing the aperture, suddenly the subject's hand-held candle, face and most of her body are in perfect focus and everything 2 feet behind them begin to blur. This is the aspect where low light and huge apertures meet in a happy medium and we get those interesting results.

[perfectoarts]

Jerry what a top article and thank you so much for taking that much time out to do so. You are an absolute genius.
I must admit I am turning into a bokeh junkie with my canon 50mm f/1.4 lens. Maybe I should post some examples here. But for now I will leave it so people can concentrate on your lovely article.