« on: December 15, 2014, 10:30:38 PM »
New member and not super techie, so please be nice. Also, I am a Tony/Chelsea fan, -- they are nice, goofy and earnest, IMHO, so again, please be nice. That said, I do get very confused by Tony's explanations. Here's why -- I think -- prior to digital phtotgraphy, using a 35 mm camera meant that light got to film causing a photochemical reaction which produced a picture. So, all the math was based on a constant. Now, there are ff digital cameras, which are "true" 35 mm equivalents and crop sensor cameras, which are camera with sensors that are smaller than 35 mm by varying degrees. In addition, the medium is not film, so instead of a photochemical reaction, the cameras are taking in information communicated by light and reacting electronically.
Since both ff and crop sensors are pocessing the same light and then electronically converting that to an image, I don't understand his comments about the same amount of light getting to the sensor. In other words, if person A is using a ff to take a picture of statue 1 with a field of view of X and person B is using a crop to take a picture of statue 1 and adjusts his position to have the same field of view of X and both are using the same lens and the same focal length, isn't everything the same? Both cameras are working to take the same eaxact picture, with the same light coming to the sensor. The only difference I can think of is that if both camera's are 20 MP then the FF pixells are going to be larger. So, I get confused about his "sensor light collecting" statements, because it seems to me that this would only be relevant if the argument was about comparing a 35 mm film camera to a smaller sized film camera. It seems to me that the argument with ff versus crop has to do with how a 20 MP ff processes the electronic information versus a 20 MP crop, not about the light getting to the sensor.
Thanks in advance for the assistance.
Tony went a little off the reservation when it came to ISO. A full frame sensor only gathers more light because it has a larger area. Crop cameras are not providing more amplification to get the same brightness because they are smaller. More than likely the 7d and 5d II provide close to the same amplification per pixel. ISO performance(noise) is largely a function of the efficiency and size of the image pixels.
His ISO noise math only works out because all the cameras used have close to the same amount of pixels. It is true when comparing film cameras. But it brakes down completely in digital where pixel pitch takes over.
Perhaps I just made his point that ISO is a bad measurement for digital. But personally I think that constant exposure behavior between camera formats is more important.
For an Ideal lens (constant intensity across the image circle) the intensity of light hitting a full frame, APC or m43 will be the same. This will lead to the same ISO, same shutter speed etc. Light intensity effects ISO. Full frame cameras have a larger Area and typically have larger pixels. Therefore it collects more total light because of its larger area. To give a crop or m43 the same total light you have to raise the light intensity.
It seems to me that the argument with ff versus crop has to do with how a 20 MP ff processes the electronic information versus a 20 MP crop, not about the light getting to the sensor.
Pretty much. Furthermore an argument about light hitting the sensor is a bit of an over simplification. Not really helpful without a discussion of pixel pitch.