help on depth of field

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wheelie2

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Hello, I'm new to photography and have just treated myself to a Pentax K100D and have been asked by a client of mine (I'm an industrial designer) to take some photos of a project we have been working on.

This is probably really simple and I apologise for my question being so basic but when I come to focus on the project which is made up of 2 components (i've tried manual focus as well as auto) to get the depth of field so that both components are in focus at the same time. I have tried moving further away which doesn't help. The lens is the standard one which came with the camera (18-55) any ideas on what I could try?

I've just posted a thread on the intro page as well - I may be of some help on printing as I print onto canvas from a Roland FJ400 large format printer and my parter is a freelance colour profiler who's been working in the industry for about 15 years, so please feel free to pick my brains and if I can help I will do my very best.... :)

Thank you in advance. :)
 
Hi Wheelie - I'm sure someone will go into this in more detail but the amount of depth of field you get is determined by the aperture. The smaller the aperture the more depth of field you get. A wide aperture might be something like f2.8 - and a small aperture might be f16, f22 or higher.

Of course making the aperture smaller means that less light is coming in through the lens. To stop the image being too dark (underexposed) you need to increase the time of the exposure. To do this you need a slower shutter speed. And if you have a slower shutter speed you will probaly get camera shake - so you need to use a tripod.

So in short - put the camera on a tripod, Set the camera to Aperture Priority (Av) Focus on the front edge of the front product - set the aperture as small as you can. If the shutter speed is very slow try using the timer function so you don't get camera shake when you press the shutter.

Take a look at the results and experiment with different apertures and distances until you get one you like.

Hope that helps
 
I could be completely off the mark here so correct me if I havent understood the problem correctly, but depth of field is dictated by the apperture of the lens not so much the focusing. Your camera should have something like an AV setting so you can set the apperture manually and the camera works out the rest... the smaller your apperture (F2.8 for example) the less will be in focus at one time so upping it to a higher F number should give the desired effect.

EDIT: Just notice the post above.. so what he said
 
Hi Wheelie - suggest you set the set the camera in a static position (on tripod or someway it will not move), then set camera to Av mode on the dial and select the lowest aperture value your lens allows (probably 4.5 or thereabouts). Then take a sequence of images each one at the value higher than the last, focusing on the front of the closest subject. You sould see that the lower the numeric aperture value, the more the background is blurred. As you get up to f11 the background will become sharper, but possibly darker (as the aperture is getting smaller so letting less light in). Go higher & more of the background becomes in-focus, but possibly darker still. Select the aperture value that keeps both the subjects sharp enough for your purpose - you may need to use additional lighting or flash to compensate for the lack of light entering the lens.
Hope this helps
Phil
I also believe that there is an option on the K100d to preview the depth of field on the lcd display somewhere in the menu options.
 
Thank you all - that's great and explains it realy well, thank you. I will go and have another play.
 
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