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Garrie
23rd November 2007, 09:53 AM
Hi,

I'm going to show my ignorace here so please excuse me.

I understand the importance of the aperture with regards to DOF etc and also how it effects shutter speed.

However my question is, Would you be able to tell the difference in a shot with the aperture of F-22 and then the same shot with an aperture of F-16 say in a landscape?

Think its my untrained eye but I can't really see a difference in DOF.

Cheers
Garrie

photonutter
23rd November 2007, 10:24 AM
DOF depends largely on the distance from the camera your focusing on and lens length used, so your landcsapes shouldnt be effected that much if your focusing on infinity at the same focal length. The longer the lens, wider apeture and nearer the focal point, the less depth you'll have in shot.

Garrie
23rd November 2007, 10:26 AM
Thanks for the reply.

So my Glasgow Armadillo shot in my Gallery wouldn't have matter what aperature I used?

Would I have got the same result using F8, that would mean I could increase the shutter speed.

Ian
23rd November 2007, 10:37 AM
Hi,

I'm going to show my ignorace here so please excuse me.

I understand the importance of the aperture with regards to DOF etc and also how it effects shutter speed.

However my question is, Would you be able to tell the difference in a shot with the aperture of F-22 and then the same shot with an aperture of F-16 say in a landscape?

Think its my untrained eye but I can't really see a difference in DOF.

Cheers
Garrie

Interms of DOF, almost certainly not as the DOF with a wide angle lens is very wide, even at full aperture. Take a 14mm lens at f/2.8 - focus on an object at 16 feet and everything about 8 feet in front of it and everything behind it out to infinity will be in focus.

Dofmaster (http://www.dofmaster.com/dofjs.html) has a great online DOF calculator that is compatible with Four Thirds cameras - have a play with it.

But at f/16 and f/22 you are into the realm of image-softening diffraction effects. This is caused because the sensor photosites can no longer resolve point details optimally because they are blurred through diffraction caused by very small lens apertures. On 10MP Four Thirds cameras the threshold is around f/8, below which resolution is gradually lost, stop by stop.

It's explained brilliantly here (http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm) - use the Nikon D2X model as the closest match for 10MP Four Thirds sensor characteristics.

At f/8, which is the optimal aperture for resolution on a 10MP Four Thirds camera, the widest DOF for a 14mm focal length lens works out at 2.8 feet to infinity.

Hope that helps,

Ian

Ian
23rd November 2007, 10:46 AM
Thanks for the reply.

So my Glasgow Armadillo shot in my Gallery wouldn't have matter what aperature I used?

Would I have got the same result using F8, that would mean I could increase the shutter speed.

Unfortunately, there is no exif metadata contained in your image (looks like you use a program that saves the edited image without this information).

But let's assume for argument's sake that you used the E-510 standard kit zoom lens at its 42mm longest focal length. Remember the rule is to avoid going under f/8 if you can, so f/8 would give you in focus detail if you focused on an object at 49 feet, from 25 feet to infinity.

Ian

Garrie
23rd November 2007, 10:51 AM
Ian, That is great, thank you, I guess that explains why my pictures are soft, I've been shooting at F-22 so the whole frame stays in focus :rolleyes:

Thanks again guys, I hope I can help others out like you have helped me out :)

Ian
23rd November 2007, 10:57 AM
Ian, That is great, thank you, I guess that explains why my pictures are soft, I've been shooting at F-22 so the whole frame stays in focus :rolleyes:

Thanks again guys, I hope I can help others out like you have helped me out :)

The only times I use anything below f/8 are when I need the extra DOF (for macro or close focus product shots, or if I run out of shutter speed at the fast end. A neutral density or polarising filter would be a better solution than going under f/8.

At f/22, the loss in resolution compared to f/8 is bordering on the severe :( and explains why you almost never see f/32 on Four Thirds lenses.

Don't be worried that in normal conditions Four Thirds might not let you stop down enough compared to larger sensor cameras for DOF. The larger the sensor, the lower the DOF is at the same given aperture and field of view. The main issue that is a problem for Four Thirds is at the open end of the lens and extreme minimum DOF for background (and foreground) blur effects. But if you step back and use longer focal lengths, you can still achieve nice low DOF effects with Four Thirds.

Ian

Garrie
23rd November 2007, 10:58 AM
Unfortunately, there is no exif metadata contained in your image (looks like you use a program that saves the edited image without this information).

But let's assume for argument's sake that you used the E-510 standard kit zoom lens at its 42mm longest focal length. Remember the rule is to avoid going under f/8 if you can, so f/8 would give you in focus detail if you focused on an object at 49 feet, from 25 feet to infinity.

Ian

Brilliant, that makes total sense. The pic was shot using F-22 and shutter speed of 60 seconds, I can;t remember focal lenght

photonutter
23rd November 2007, 05:34 PM
But at f/16 and f/22 you are into the realm of image-softening diffraction effects. This is caused because the sensor photosites can no longer resolve point details optimally because they are blurred through diffraction caused by very small lens apertures. On 10MP Four Thirds cameras the threshold is around f/8, below which resolution is gradually lost, stop by stop.


Ian

Take it this is why you can get a star filter effect on night shots with long exposures