08 July 2009

Depth of Field

This week's photography tips post, please check in the left side bar for all my other posts in this series.

The Depth of field is the distance in front of and behind the point of focus that is acceptably sharp and it is controlled by varying the aperture, which is an opening in the lens that narrows and widens to allow more or less light in, measured in increments called f-stops. (easy right!).

I hope you can see a difference above! In both shots the main subject is in focus, however the shot on the right is a better photo because the background is blurred allowing you to concentrate on the beautiful sea holly.

I took these shots using the aperture priority mode, the one on the left has the aperture 'stopped down' to it's narrowest point (in my case F/8)and the one on the right has the aperture set as wide as possible (F/2.8). Photographers taking portrait shots will often use a wide aperture to blur the background, making the subject stand out sharp and anything distracting behind fade away, this is why you might see a portrait mode on your point and shoot style camera, all it's doing is opening up the aperture while the landscape mode is doing the exact opposite.

You'll see examples of photographers using wide apertures a lot to single people out in a crowd or to make a sportsman stand out from the crowd. Once you understand this you'll start to see examples all over the place, just browse through any newspaper or magazine.

Of course the opposite is true too and when you are taking photographs of distances or where you want as much to be in focus as possible you should 'stop down' or turn your dial to the narrowest aperture the light will allow (using a tripod helps with slow shutter speeds).

In this picture of P on the London Eye, I was aware that if I didn't use a narrow aperture to increase the depth of field I was in danger of P being out of focus - bear in mind I was in there with 16 other tourists (and sweaty ones at that) and I didn't have much room to stand back or manoeuvre at all!

Talking of trying to get as much into the plain of focus as possible brings me back to craft photography (finally).

When you use the macro function on a lot of point and shoot cameras (mine included) the depth of field really suffers which is unfortunate because as you are usually shooting on a plain background it would be beneficial to have every part of the image in crisp focus.
Look how narrow the depth of field in the above shots is - I focussed on the larger blue millefiori bead, with the shot on the left at its narrowest aperture (F/8) and the shot on the right at its widest (F/3.2), just a few 4mm beads behind the focal point and they are already losing focus even at it's narrowest aperture.

Many cameras will have apertures that will stop down to F/16 which would help, not mine unfortunately! So taken at this angle it would be impossible to have this tiny bracelet completely in focus using my camera on its macro setting.
With Etsy we are lucky to have 5 chances (3 on Folksy) so we can allow ourselves to be more creative with close ups. I would use this picture to really draw the eye into that beautiful blue millefiori bead and then take a more traditional picture from above of the entire bracelet in sharp focus so the buyer can see exactly what they are getting (I'd let loose with the rest and be sure to fill up all 5 slots!)

So it is crucial in macro mode that you compose the shot and focus really carefully in order to ensure that you are showing the potential buyer your piece to it's best - with a narrow depth of field you can create some really dynamic pictures that draw the eye to special details on your piece, I often use this angle on my bead kits for that very reason.

One last point - If you are photographing large paintings or similar it is important to 'stop-down' (F/8 or F/16) to ensure the corners of the painting are in sharp focus as even though it is a flat plane they are further from the lens than the centre of the painting which is the focussing point.

More tips next week! There's still lots to talk about...