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 Post subject: Olympus (4/3) DOF
PostPosted: Fri Jun 22, 2007 2:13 pm 
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Location: Copenhagen, Denmark
I was wondering how well the 4/3 system does in DOF? I was reading the lates review of the 4-17/4 and was thinking this must have a really large minimum DOF with f/4 on these focal lengths, and how large is it on the other lenses.

I like the idea of the much faster lenses but is it a compromise or can you still make DOF like 50mm f/4 and still with sharp results? In the other reviews the lenses is usually stopped down to f/8 to produce sharper results, would you still need to do that on an 4/3 lens?

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Minolta primes: 2.8/20 2.8/24 1.7/50 2.8/135
Minolta zooms: 28-135 35-70 70-210(beercan) kit
Minolta cameras: Dynax 5D 7000
M42: Pentax Asahi S-M-C Takumar 1.4/50 and 2.8/105 Carl Zeiss Jena Flektogon 2.4/35 Industar-61L/Z Kiron 2.8/105 Macro


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 Post subject:
PostPosted: Fri Jun 22, 2007 10:31 pm 
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Location: Queenstown, New Zealand
Hi Rune, that's a great question.

The slightly smaller sensor in the Four Thirds system does mean there's a slightly larger inherent depth of field at a given aperture. It also means the optimum aperture for lens sharpness should be slightly smaller than the typical f8 of most other systems.

That's the theory anyway.

In practice when I do the resolution results I shoot the chart at every aperture and select the sharpest results. And for recent Four Thirds tests, I found the best results were at f8, although f5.6 and f6.3 were pretty close. Like all lenses, it's a case of doing some of your own tests and find the sweetspot if that's something you're into.

As for DOF, you can see in this shot taken with the E-410 and 14-42mm at 42mm and the aperture wide open, that the DOF is still quite large - certainly larger than most other kit lenses zoomed-in with their apertures open.

Image

But you can get nice and fast lenses for the Four Thirds system, and they can produce very small DOFs if required. The 50mm f2.0 for example is a lovely lens.

Gordon


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 Post subject:
PostPosted: Sat Jun 23, 2007 12:32 am 
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Joined: Thu May 31, 2007 11:22 pm
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Location: Northern Virginia, USA
Just to add to Gordon's already excellent expanations and exemplification:
The DOF gets shallower when:
- the sensor size increases
- the distance between the subject and the lens decreases
- the focal length of the lens increases (prime or as a result of zooming in)
- the aperture is enlarged
- the lens is switched to the macro mode (if available)

The sensor size is a given with any camera (except backs :) ) but you can adjust the other 4 factors (within some limits) to get (as close as possible to) the desired DOF.

Darrin

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 Post subject:
PostPosted: Sat Jun 23, 2007 10:09 am 
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Joined: Mon Apr 30, 2007 10:55 am
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Thanks for the explanations. 42/5.6 would be something similar to 84/11 which actually looks great but might be too large for some shots :?: If the aperture is too large and closed focused I find that you get strange out of focus experience, so this must be an advantage of 4/3 system that you can get fast lenses without strange bokeh at close focus :)

It’s interesting that you have to stop it down to f/8 to get the sharpest picture, that could take some of the advantage away I guess. How did you find the handling of bokeh when you tested the Olympus.

_________________
Minolta primes: 2.8/20 2.8/24 1.7/50 2.8/135
Minolta zooms: 28-135 35-70 70-210(beercan) kit
Minolta cameras: Dynax 5D 7000
M42: Pentax Asahi S-M-C Takumar 1.4/50 and 2.8/105 Carl Zeiss Jena Flektogon 2.4/35 Industar-61L/Z Kiron 2.8/105 Macro


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