Olympus OM-D EM-5 Discussion

brian1208 (e2 Member)

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2 Sep 2012 - 10:37 AM

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Quote: but not in terms of light gathering

that's the important bit as far as I am concerned, a bit more DOF can be useful but its good to keep the light

Carabosse (e2 Member)

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2 Sep 2012 - 5:41 PM

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Quote: A 50mm lens might give you a 100mm crop but as dof goes it will still be that of a 50mm.

The DoF of an f1.4 lens on M4/3 will be the same that of an f2.8 lens on 'full frame' (i.e. 36 x24mm sensor). Are you seriously disputing that?

Which is one of the reasons why there is a market for such things as f0.95 lenses for M4/3.

mdpontin (e2 Member)

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2 Sep 2012 - 7:45 PM

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Okay, I admit it, I have no idea what you're talking about. Care to explain?

Carabosse (e2 Member)

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2 Sep 2012 - 8:20 PM

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Quote: There s a bit more two it than focal length

I for one am not talking about focal length at all!

What I am saying is that the depth of field (but not light-gathering power) of a lens used on M4/3 at a given aperture is the same as that lens used on FF at double the f-stop.

Viz. The DoF of the Oly 45mm f1.8, at max aperture, is the same as that of a 90mm lens at f3.6 on FF.
the DoF of the Panny 20mm f1.7 is the same as that of a 40mm at f3.4 on FF.

Some people delude themselves into thinking that if you put, for example, a legacy 50mm/f1.4 lens onto M4/3 you will effectively get a lens with the angle of view of a 100mm (on FF) but with the DoF of an f1.4. Which is wrong. The DoF is that of a 100mm at f2.8 on FF.

Hope that's all clear!

Paul Morgan (e2 Member)

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2 Sep 2012 - 8:26 PM

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Stick a 50 on a crop then a 50 on a 35mm, on the 35mm the 50 has more dof, go and look at some calculators

Paul Morgan (e2 Member)

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2 Sep 2012 - 8:53 PM

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Quote: What I am saying is that the depth of field (but not light-gathering power) of a lens used on M4/3 at a given aperture is the same as that lens used on FF at double the f-stop


Quote: 50mm f1.4 on M4/3 = same DoF as 100mm f2.8 on FF

Now your comparing two different lenses

brian1208 (e2 Member)

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2 Sep 2012 - 9:50 PM

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I can't get the pics to show

There they are!

mikehit (e2 Member)

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3 Sep 2012 - 8:38 AM

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Quote: There s a bit more two it than focal length

I for one am not talking about focal length at all!

What I am saying is that the depth of field (but not light-gathering power) of a lens used on M4/3 at a given aperture is the same as that lens used on FF at double the f-stop.

Viz. The DoF of the Oly 45mm f1.8, at max aperture, is the same as that of a 90mm lens at f3.6 on FF.
the DoF of the Panny 20mm f1.7 is the same as that of a 40mm at f3.4 on FF.

Some people delude themselves into thinking that if you put, for example, a legacy 50mm/f1.4 lens onto M4/3 you will effectively get a lens with the angle of view of a 100mm (on FF) but with the DoF of an f1.4. Which is wrong. The DoF is that of a 100mm at f2.8 on FF.

Hope that's all clear!

My understanding is that calculations of depth of field make assumptions about the physical size of the image and the 'normal viewing distance' which itself is related to the size of the image. If you print an image bigger but view it from the same distance then DOF becomes shallower because the areas at the limit of DOF are more obviously blurred (in much the same way that an image on the back of the camera looks sharp but is well out of focus when seen on the computer screen). Now cropping and blowing up is the same as printing bigger and viewing from the same distance.

PS - I do agree with Paul that you would have the field of view of a 100mm lens but the DOF of the 50mm lens at f2.8.