Tag Archives: focus

GX1 Depth of Field

Shot on a Panasonic GX1 with Olympus 9-18mm lens set to 10mm. I used f/9.0 for this image and whilst its sharp it would have been better at f/7.1. I didn’t have my depth of field scale with me and couldn’t take any chances. Click the image to see a larger version.

I am growing tired of seeing the same advice trotted out time and time again about Landscape Photography. The advice that has me so wound up is that “if you want to get a full depth of field you need to use a very small aperture”. This advice has almost been carved in tablets of stone for all to see. Does it work; yes it does BUT IT ISN’T THE BEST ADVICE.

To me, this advice is almost the lazy way to photograph landscapes. The advice you should be getting is to shoot your landscape with the best aperture (the one that gives you the highest quality image) whilst still giving you the required depth of field. To understand why and why this is so important for Micro 4/3 and compact camera photographers you need to understand a few basics about lenses and depth of field.

Firstly most consumer lenses are designed to achieve their sharpest images and resolve the most detail when the aperture is closed down about 2 stops from wide open. For many lenses this means you will get the best results at around f/8 to f/12. Either side of this range you will find the image just isn’t as sharp and if you stop down the lens to around f/22 you might find all sorts of distortions can kick in. Buy the best lenses you can and you might see some improvement on this.

Now the thing with Micro 4/3 cameras is they seem to hit their best performance when stopped down just a little bit and the best way to understand this is by testing your own lenses. I haven’t done extensive testing but with my 14-45mm lens, I tend to shoot landscapes at between f/5.6 and f/7.1 for the 14mm end of the zoom range. I have found that if I stop down to f/8 or beyond then it’s not quite as sharp.

So you know the aperture range where your lens performs best, how do you ensure there is sufficient depth of field? The answer is by selecting the correct point of focus first and then selecting the correct aperture in this range. This is probably best explained with an example.

Suppose you find a nice landscape scene and there is a lovely rock that you want to place in the foreground. You compose the shot with your camera mounted on your tripod at just below eye height and the rock is about 5 feet from where you are stood. The distance from your camera to the rock is probably going to be about 7 feet. If I consult my depth of field chart (it’s actually an app on my phone) I find that focussing on the rock with my lens set to 14mm (on the GX1) the widest aperture that allows me to achieve infinite depth of field is f/6.3 – yes you read that right. The nearest point to me that is in focus is actually only 3.4 feet away.

Taking a more extreme example lets lower our tripod and move in close to the rock so that it looms large in our viewfinder. Unfortunately the 14mm lens isn’t wide enough so we move the Olympus 9-18mm set to 10mm. This is the equivalent of a 20mm lens on a full frame camera. Having moved in close we find our point of focus on the rock is just 4 feet from the camera. Looking at my depth of field app I find that I can achieve infinite depth of field at just f/5.6 and the closest point in focus is just 1.9 feet from the camera. At this aperture my lens is going to be performing at its sharpest and resolve the maximum amount of detail. The images produced will be substantially better than if I had used a small aperture such as f/16. Just for fun I thought I would check the aperture I needed with my 5D and its f/11.

Do you think you think you have been selecting the best aperture for your work?