I recently bought me an adapter for using my fathers old lenses (Leica R 35,50,80,180 and 250mm) on my Lumix G3, and I was somewhat disappointed on bokeh results. By help of your explanation above, I understand why, and I know how to work on this. Thanks for this.

I have an other question that is related to this kind of hardware setup: Every lens produces a circular picture that is projected on a rectangular film or sensor inside the camera. When combining full frame lenses with full frame camera, one can calculate that +/- 59% of the circle area is projected on the rectangle area. The remaining 41% of light is absorbed by black paint inside the camera as much as possible. In a configuration of a full frame lens with a micro 4/3 camera, one can calculate that only +/-15% of the light hits the sensor, and 85% needs to be absorbed!!!. Knowing that there is no paint yet that fully absorbs light, I wander if there is no visible bad influence of this reflecting light that is present in a quantity out of proportion inside the camera? I am wandering also if micro 4/3 camera producers design the full larger zone around the sensor for an optimal light absorbtion? It was these scientific facts that made me hesitate longtime for buying an adaptor. What is your experience or opinion in these?

Thanks,
Dominiek

“If you slap a 25mm F2 lens on a m4/3 camera it will be like shooting with a 50mm in regards to focal length, but your depth of field will be that of a 25mm lens at F2, not a 50mm lens at F2.”

Like this:

“For 35mm film, or equivalent sensor size (full-frame), a 50mm lens has a (diagonal) angle of view of roughly 47 degrees. If you slap a 25mm f2 lens on a m4/3 camera, the angle of view would be nearly equivalent to full-frame 50mm, but the depth of field remains a function of the actual focal length of the lens at f2, and not the angle of view.”

Similarly this line would need to be rewritten:

“The sensor size turns the lens into a 50mm focal length but you are still shooting with a 25mm lens…”

To be more like this:

“While the sensor size (crop factor) gives you the equivalent field of view of a 50mm lens on a full-frame camera, you are still shooting with a 25mm lens”

Thanks Steve.

Please note that 1 lux is a RATIO and as such is independent of TOTAL SURFACE AREA.
It appears that you have confused PIXEL size with SENSOR size and signal to noise ratio with exposure value. For the sake of clarity it needs to be established that they are independent concepts.

If I use an f2 lens on an imaging device and take an image of a uniformly lit white surface, when I calculate the desired exposure value when shooting at f2 1/100″ that is what I get – at ANY POINT within the image circle (ignoring vignetting problems for the sake of this discussion). Cropping the sensor IS NOT the same as using an extension tube or teleconverter because the total size of the image circle remains the same and therefore the intensity of light at any given point in that circle is not affected.

What you are probably trying to conceptualize is more of an argument related to pixel size. If all other things are equal (microlens spacing, efficiency and transmissivity, photodiode sensitivity and other circuitry) a sensor with larger PIXELS (completely independent of total sensor size) that sees the same intensity of light as a a sensor with smaller pixels will indeed collect more photons PER PIXEL (because those pixels cover a wider area). At the pixel level, we are now talking about a TOTAL # photons and not just a ratio.
To restate: Because the light INTENSITY is uniform, a larger PIXEL will be impacted by more photons than the small pixel. With more photons being “counted” by the larger pixel, the signal to noise ratio may be higher (assuming all other things being equal including ideal scalability it WILL be higher).

You are correct in stating that each sensor has the gain set for it – the manufacturers take into account the signal-to-noise ratio as well as the “well capacity” and the sensor’s response profile when determining the amount of gain to apply to the sensor (i.e. how little noise vs how easy to blow the highlights?).

The argument that you make is related to PIXEL size and not directly to sensor size (compare Nikon D3X vs D3s ISO performance) – furthermore, when you shoot a Nikon D3x in crop mode you will notice that aperture/shutter speed/ISO do NOT change to maintain the same exposure for the ‘cropped’ area (yes, that means that even behind the scenes the sensor GAIN does NOT change).

Sorry about the length of the pose but I hope this helps – more knowledge is always better IMO.

Steve: Thanks for your work in providing this great comparison for those of us who are truly interested in the topic you present (DOF comparison) and discussion you provide.

Cheers.

Light that comes from an apple on the edge of the picture physically came from that apple. It can’t be magically converted into light that came from an orange in the center of the picture. No matter what you do, if you want that photon, you’ve got to use it to show the apple. If you don’t show the apple, you don’t get to use that photon.