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Robusto
4th April 2011, 07:12 PM
A little help needed

Started using my new E30 over the weekend with the 50-200 for football shoots

my question how do i get my subject in focus and the background to blur

here i have a picture (bird) taken on the E300 with 70-300 with blurring

then here is one take over the weekend (football) how do i get the background blur

regards

Ouch!
5th April 2011, 11:04 AM
Right I'm a beginner in the world of digital photography but what you're talking about is 'depth of field'.

Depth of field relates to the furthest and the closest parts of the picture that are in sharp focus.

When you have you nice zoom lens at the long end (i.e 300mm) the depth of field is shorter than the other end (i.e.70mm). So, the subject is sharp and the background (and forgorund) will be blurry. To accentuate this, you can open the apature wide. This uses more of the lens and so less of the picture will be in sharp focus; less depth of field. By closing the apature you only use the little centre portion of the lens and more of the photo will be sharp, both in front of and behind the subject.

If you want the background to blur, use your widest apature setting and longer lens and compensate with a faster shutter speed. (Or even a nuetral density filter if the image is too bright).

Most photographic websites will explain depth of field, better than me, but I hope this makes some sense.

My old OM system lenses, even had the depth of field marked on them at different f numbers. So if you wanted to blur the background you could slightly over focus the lens, putting the subject at the back of the depth of field, therefore guaranteeing that the background would be blurred. These helpful marks do not seem to appear on the modern auto-focus lenses.

Ouch!

Ian
5th April 2011, 11:25 AM
Hi Martyn, basically to blur the background more than you already have you need to reduce the depth of field (the range in front of and behind the focussed subject) that is in sharp focus. You can achieve this in two ways: open the aperture up (try the 50-200 @200mm using fully open aperture f/3.5), and get closer to the subject. The closer you focus, the less likely the background will be well defined.

In the pigeon shot you are closer and the 70-300 is longer focal length (300mm compared to 200mm) - so the depth of field is much smaller.

Best way to demonstrate this is to try it out :)

Ian

wanderer
5th April 2011, 11:28 AM
I would also add that when focussing on a relatively near object (the pigeon) the depth of focus is a much shorter distance than on a far object (the footballer). So the background on the near object is thrown out of focus more than the far object.
In numbers; the pigeon looks about 5 metres away and the background 10 metres. The depth of focus is probably from 4 to 6 metres at best and probably half that.
if the footballer is 30 metres distant the focus is likely to be 27 to 35 metres with the goalpost still recognisable at double that. If the aperture is F8 rather than F4.5 the depth of focus is even greater.
As above therefore the footballer should be photographed with the aperture wide open (4.5 thereabouts) and this consequently means a faster shutter speed which helps to freeze the action.
It is often difficult to get a background that is a general blur. Usually there is something that betrays itself (goalpost). This is because you are concentrating on the action rather than the background. And its surprising how often it sticks out of the person's head.:)

danellis
6th April 2011, 01:07 PM
So the number after the f needs to be as small as possible?

dJE

StephenL
6th April 2011, 01:33 PM
Amended version following Bikie John's correction

The smaller the f number the larger the aperture therefore the shallower the depth of focus. ie f4 will show less sharpness to the front and rear of your subject than f8.

Don't forget to put your camera in A (aperture priority) so that the shutter speed is automatically adjusted to compensate.

Bikie John
6th April 2011, 02:14 PM
The larger the f number the larger the aperture therefore the shallower the depth of focus. ie f4 will show less sharpness to the front and rear of your subject than f8.

Bit of finger trouble there, I think. The smaller the f number, the larger the aperture therefore the shallower the depth of focus. So as Stephen says with f/4 there will be less sharpness in front and behind than with f/8, which is what you want in ths case. Smaller f-numbers also allow faster shutter speeds so are better for freezing movement - so generally for sports work small f-numbers are good.

Sorry to be picky, but I thought it looked potentially confusing as written.

Ciao ... John

StephenL
6th April 2011, 02:30 PM
Sorry you are quite right! Getting confused - it's my age you know!