Comparing Olympus 4/3lenses to FX "Full Frame" offerings

Started Jan 25, 2014 | Discussions thread
bobn2 Forum Pro • Posts: 51,019
Re: remaining "ignorant"

Tiger1 wrote:

Ian Stuart Forsyth wrote:

Tiger1 wrote:

Agree with the good doctor.

F1.8 = F1.8 on ANY format.

If you don't realise this you must go back to school and repeat first grade.

Depth of field changes with format because to get the equivalent view on a smaller format you must use a lesser focal length which automatically increases the depth of field.

Simple, really.

Let’s look at light as if it was paint coming from a spray can. The lens AP controls the intensity of the paint being applied to the surface of the sensor and they both receive the same duration. At the end of that time which sensor has received the most amount of paint ?

Sure they have the same thickness of paint applied to their surface but one has more paint applied to its total surface any guess which one?

Now what would it take for that smaller surface to receive the same total amount of paint if the duration was held the same. One could try and amplify the paint but that won’t work as we cannot create matter. Then I guess all that we can do is increase the intensity of the paint hitting the surface of the sensor by opening up the lens equal to the size ratio of the 2 sensors.

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Well well well!!! By your own admission the same thickness of paint is applied to each surface!!!

Isn't that the same as the intensity of light hitting per unit area?

If the same intensity is hitting the sensor then the photosites are getting the same amount of light!!!

Yes we know the photosites are smaller and thus collect less light per photosite. Nobody is disputing that fact and that is why a Nikon Df has much better noise characteristics than an Olympus EM-1.

Think abut what you're saying, if it were true the Df would have 'much better' noise characteristics than the D800, and it doesn't. Photosite size has a very small effect on the efficiency of a sensor. The idea that it is the major thing that determines how well a sensor works is one of the persistent myths around on these forums, and it is persistent because people need it to sustain the false argument that it is exposure (light density) per se that determines image quality, rather than the total amount of light captured in the image.

What we are disputing is that when it comes to light gathering per unit area, F stops are the same no matter what the format. As some has already said, if that wasn't the case hand held light meters would not work!

No-one is disputing that at all. The question under dispute is what is the effect of equal light gathering per unit area - does it imply equal noise characteristics of an image for different size images, and the answer is that it doesn't. This argument has nothing at all to do with the sensor, the noise (photon shot noise) is built into the image itself, and the fact of the matter is that with equal exposure (light gathering per unit area) the image projected onto a FF frame will have twice the SNR as the image projected onto a Four Thirds frame. If you want equal SNR then the FT image needs four times the exposure compared to the FF frame. If the shutter speed is held constant, that means half the f-number.

I've owned 8x10 cameras, medium format, 35mm, digital cameras of varied sensor size. When I use my light meter and it gives me a shutter speed and F stop it works for ALL those formats!!!!

Of course it does, that is what it is designed to do. Did you have any f/1.4 lenses for your 8x10 cameras?

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