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03-20-2012, 02:01 AM   #1
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Noob question f2.0 for M4/3, APS-C and 35mm, What is the difference

Beside depth of field? will they provide the same 'speed' (size of aperture opening to allow light in) in different sensors size?

IF this is the case say you want deep DOF and your subject has some movement, so you use f8 on FF to provide that but in failing light you have to make do with higher ISO right? Under the same scenario if you have a M43 you could achieve the same DOF with say f5.6 and get away with lower ISO yes? What did I miss?


Last edited by lightbulb; 03-20-2012 at 02:09 AM.
03-20-2012, 02:35 AM   #2
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sounds about right, with smaller sensor sizes, you get more apparent depth of field. So handy thing about this is that if you want to get the same apparent depth of field on a 100mm @f8 on FF, you can use a 70mm @f5.6 on apsc or a 50mm @ f4 on m4/3. The amount of light transmission doesn't change from format to format, only the apparent depth of field.
03-20-2012, 04:39 AM   #3
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theoretically it seems m 43 is good for certain situation then. they should make more F2 zoom due to weight advantage me think.
03-20-2012, 07:36 AM   #4
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QuoteOriginally posted by lightbulb Quote
Beside depth of field? will they provide the same 'speed' (size of aperture opening to allow light in) in different sensors size?

IF this is the case say you want deep DOF and your subject has some movement, so you use f8 on FF to provide that but in failing light you have to make do with higher ISO right? Under the same scenario if you have a M43 you could achieve the same DOF with say f5.6 and get away with lower ISO yes? What did I miss?
Yes, but given the same sensor technology the larger sensor will have better noise characteristics at higher ISOs than the smaller sensor, so you can afford to stop down and raise the ISO to maintain the shutter speed.

03-20-2012, 08:03 AM   #5
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True too, but given the weight and price issue, M43 and APS-C make better sense for outdoorsy works I would think.

Side track a bit; I was thinking about getting the 5D mark III with 24-70 2.8 L lens and then the Photozone reviewed the lens after '3rd' tries to find a 'okay' copy. QC problems not only plague Pentax, even Canon has its share of problems!

I am glad to have K5 and 18-135.
03-20-2012, 09:53 AM   #6
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If you google the term "equivalence" as it relates to photography, you will find a wealth of info - much of highly mathematical and hard to digest - on the subject. But the basic bottom line is that yes, just as there is a "crop factor" that explains how the angle of view of lenses compare between sensor sizes, a similar concept explains how the apertures compare. And the bottom line is that 50/2 on APS-C is almost exactly equivalent in all respects (AOV, DOF, and amount of noise one can expect for a given shutter speed) to a 75/2.8 on FF.
03-20-2012, 09:55 AM   #7
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QuoteOriginally posted by Marc Sabatella Quote
If you google the term "equivalence" as it relates to photography, you will find a wealth of info - much of highly mathematical and hard to digest - on the subject. But the basic bottom line is that yes, just as there is a "crop factor" that explains how the angle of view of lenses compare between sensor sizes, a similar concept explains how the apertures compare. And the bottom line is that 50/2 on APS-C is almost exactly equivalent in all respects (AOV, DOF, and amount of noise one can expect for a given shutter speed) to a 75/2.8 on FF.
or a 25 1.4 on m4/3
03-20-2012, 09:59 AM   #8
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Don't forget also that larger sensors have better Dynamic Range and better colour sensitivity. APS-C is well ahead of four thirds using these measures.

03-20-2012, 08:32 PM   #9
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Yeah, I am holding back my horses for OMD EM5, If they had 720P in 120fps and f2.0 12 to 50 zoom WR I had be all over it. Yes, speaking of DR and Colour Depth I could get used to a 16-50 Mark 2 and K3 with articulated screen, dedicated video button, 720p 120fps, and more AF points (read smaller). I am very pleased with K5 as of now.
03-21-2012, 01:18 AM   #10
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QuoteOriginally posted by eddie1960 Quote
or a 25 1.4 on m4/3
Actually it would be around 37/1.4 on m4/3. I say 'around' because although 135/FF and m4/3 (I think) have standard frame sizes, what we call APS-C can have frames of varied sizes. But let's assume that, based on the defined 135/FF frame of 36x24mm, the format.faktor for APS-C is 1.5 and for m4/3 is 2.0. Then a 50/2 on APS-C has about the FOV and DOF of a 75/2.8 on 135/FF and a 37/1.4 on m4/3.

So if we used lenses with those focal lengths (assuming they have the same light transmission) on those formats to shoot a subject from the same distance at the same aperture, the images should look the same -- same FOV, DOF, and perspective. This disregards any differences in resolution and diffraction limits. Lotsa caveats there, eh? It's easy to say, "With all else being equal, this produces that" but it's hard to keep all else equal.

In practice, we make adjustments. If I put an old manual full-frame lens (with nicely-inscribed distance-DOF scales) onto my K20D, I mentally adjust by 1 f-stop. So if I've set the aperture to f/11, I read the DOF scale at (or just inside) the f/8 marks. If I'd put that lens on an m4/3 camera, I'd read at the f/5.6 marks. And for hyperfocus, I'd fudge those numbers a little, to ensure that infinity *IS* in focus.

What the hell, drawing equivalences between formats is tricky. And DOF is a complex product of photography, presentation, and psychology. And lenses are built within real tolerances, so none of these numbers are constant and exact. We just have to live with approximations.
03-21-2012, 02:37 AM   #11
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This article may be worth a read OP:

Digital Camera Sensor Sizes: How it Influences Your Photography
03-21-2012, 04:12 AM   #12
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Along the logic of the OP, if you are always looking for maximum DOF. Get a bridge camera sensor technology has improved since my old Kodak DX7590' but it was a very capable camera at ISO below 100 and with a 36-360 (35mm equivalent) at F2.8-3.6 it is hard to beat in terms of size and weight for the equivalent focal length and speed of lens. Things have only gotten better since I goth that camera in 2004
03-21-2012, 07:13 AM   #13
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Thanks guys very good information from all of you!
03-21-2012, 08:24 AM   #14
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QuoteOriginally posted by Lowell Goudge Quote
Along the logic of the OP, if you are always looking for maximum DOF. Get a bridge camera
Or a Q, or Nikon 1.
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