Crazy disinformation about DOF, 4/3 f-stop vs 35mm, microlenses

Started Nov 22, 2011 | Discussions thread
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Crazy disinformation about DOF, 4/3 f-stop vs 35mm, microlenses
Nov 22, 2011

In another thread a bunch of people have been calling each other names, posting disinformation about how 4/3 DOF isn't the same at a given f stop, how lenses greater than f/2 are wasting the light.

So I did a little messing around with my E-30 and f1.4, f/1.8 and f/2.8 lenses and my trusty old Minolta X-700 and XG-1.

My Sigma miniwide f/2.8 28mm MC on both my Minolta and my E-30 delivered the same depth of field. Granted, on my Mintola its a 28mm lens and on my E-30 acts like a 28mm lens cropped to a 56mm field of view , but that didn't change the depth of field one bit. Bookeh is THE SAME! So all this hoey about DOF not being the same merely because its a 4/3 sensor is just that, HOEY. I agree DOF isn't the same from one lens to another, and the DOF of my Sigma miniwide f/2.8 isn't the same as my Oly 14-54 II at 28mm or my Sigma 1.4 30mm. Its just different, and is one of the inevitable compromises made when designing a lens. But this two stop rule of thumb is a steam pile of cat poo.

Oly microlenses making anything greater than f/2.0 a waste on 4/3 is a big steaming load of horse droppings. Using wide open aperturers on my Sigma f/1.8 24mm and Sigma f/1.4 30mm gives me precisely the change in exposure I expect, a full stop of aperture means I need 1/2 the shutter speed. And this happens at 3200 ISO on my E-30. If Olympus was cranking up the ISO to compensate for faster glass that they can't take advantage of then the image noise would change, but it doesn't. Not a bit.

Last but not least, I have heard sage advice here that an f/2 4/3 lens delivers the same light as an f/4 lens for a 35mm camera. Again, pure steaming donkey manure, anyone that uses legacy glass (like me) doesn't magically end up with a faster lens when they put it on a 4/3'rds camera. The metering is THE SAME. If you want to count photons that could be delivered over an entire photo sensor then you might have a point, but its not like collecting four times the photons and spreaing them over a four times larger surface with four times larger photosensors gives you an automatic reduction in sensor noise. If that were true, the Nikon J1 would be horrific at 1600 ISO...and no point and shoot with its pinky fingerrnail sized sensor could deliver a usable image even at 100 ISO. There are tradeoffs with larger semiconductors, for instance they produce more Thermal and Shot noise. Smaller semiconductor junctions produce less self-noise, its all a tradeoff. I'm not saying bigger sensors don't offer any advantages, they do. But its not as cut and dried as some seem to think.

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 dkadc's gear list:dkadc's gear list
Olympus OM-D E-M5 Olympus E-M1 Olympus 12-40mm F2.8 Olympus 40-150mm F2.8 Pro +7 more
Nikon 1 J1 Olympus E-30
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