Lawrence Ripsher

Depth of Field

This will be a short post…

There are a number of reasons why Full Frame can make a difference to a photographer's images. Perhaps the one most commonly cited is that compared with cropped sensors (1.5x, 1.6x etc as found in the Canon 40d / 50d, Nikon D300, etc), you get a larger sensor. A larger sensor means more space to fit pixels onto which means lower pixel density for the same number of megapixels, or more megapixels for the same density. The result therefore, in theory, should be higher megapixels, less noise, or both. In practice it's often true as well.

The other benefit of FF is that lenses work as they should. A 24mm lens on a Nikon D300 gives a field of view which is actually equivalent to a 36mm (1.5x) on a FF camera. So lenses work as they should and wide lenses look really nice and wide. Of course, there is the downside for sports / nature photograpers who want telephoto reach (and therefore like the multiplying effect). Of course there's the retort that higher megapixels in FF mean you can crop more later on anyway… but this is off topic.

What I really wanted to talk about was what I perceive to be the greatest benefit of FF – shallow depth of field. Shallow depth of field (DOF), when produced through good glass and a competent photographer, is one of the most creative tricks that can be applied in photography. In allows for subject isolation, for a dreamy effect to be applied, for a different perspective than what might be normally seen, or all of the above.

The best way to get shallow DOF is to shoot with fast glass. High ISO performance in modern cameras like the 5D Mark II is making fast glass less important. Now a photographer with a good camera and an f/5.6 lens can shoot at the same shutter speed as a photographer with an f/2.8 lens by going two stops higher in ISO. With a Nikon D3, Canon 5D Mark II or a handful of other cameras, that higher ISO does not always mean a worse picture. The speed that fast glass provides, and comes at such a price premium, is still important – but the importance is not what it was.

However, there's still no way to fake shallow depth of field (ignoring post processing). And that's where good glass comes in. It's so important to me in my photography that I shoot prime lenses 95% of the time. It's also so important to me that I do not ever consider switching back to Nikon due to the fact that Canon produces a 24mm f/1.4 and a 35mm f/1.4 and Nikon does not. And as I mentioned above, it's the most important benefit of Full Frame.

I don't shoot with shallow DOF all the time. Like any ingredient, too much of the same thing can be a bore. Subtlety and choice is the key. But having the right tools in the first place certainly helps. The reason I make a big deal about it here is because very rarely talked about in reviews. Again, with most things that are important in photography, there is no scientific way to measure it. And if you can't measure it, you can't draw a chart. The good news about prime lenses is that with most brands, you can buy a cheap 50mm f/1.8 to get started if you have not already. I preach the virtues of prime lenses in a previous post.

To give an idea of what Full Frame and a good lens gives you, here are a few examples. Again, no lens charts – just a few examples of why for most photography, full frame does offer a genuine benefit over just megapixels. These were all taken in the last few days with the 5D Mark II.

24mm f/1.4

ISO 200, f1/1.4, 1/400s. Converted from RAW, some minimal processing. I liked the distortion effect I was able to achieve with the wide angle as well.

35mm f/1.4

ISO 6400, f/1.4, 1/60s. Shot in JPG. With another system or camera this simple snapshot might have been is an impossible photograph. A glance at the settings (ISO 6400 and f/1.4) should give an indication as to how little was available. The subject isolation caused here is quite remarkable (it almost looks like selective sharpening which it is not).

50mm f/1.4

Although there is a faster and more expensive 50mm f/1.2, I shoot with the f/1.4. I've provided two examples here with the 5D Mark II.

ISO 320, f/1.6 (so not quite wide open), 1/320s. Shot in RAW and converted with little processing to speak of.

ISO 500, f/1.4, 1/100s. Shot in RAW and converted. A bit of processing on the colours but not much else. Composed in live view with the camera near the ground. I liked the swirling bokeh in the foreground of this image.

85mm f/1.8

Again, Canon makes a faster lens – the practically legendary 85mm f/1.2 – but it's very specialist and does not focus as fast as the cheaper and more better allrounder f/1.8.

ISO 640, f/1.8, 1/125s. Shot in RAW and processed to create the "high key" effect. You can see here the sharpness in the eyelashes contrasted with the ghostly out of focus ears, hair, etc (the model is part submerged in the water).

So no conclusion here – there isn't anything unique about the 5d Mark II compared to other full frame cameras in this respect, but it is an important point and one I wanted to share and illustrate through a few examples. More soon…

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