Deanie1113 wrote:
I'm a little confused about sensor size. I'm looking at a Sony RX 10 IV that has a "1.0 CMOS sensor" having 20.1 mp and also the OM-D E-MI 11 having a "high speed 20 mp Live MOS sensor." What is the difference here? To me the main things that matter are light weight and image quality. The Oly is a bit more expensive and I get that I can put different lenses on it, but I really just want this camera for birding and sports action and would buy the 75-300 zoom and leave it on always. I have my Nikon dslr for everything else. Can someone clear this up for me? Thank you!
I'm a little confused about sensor size. I'm looki... (
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Don't know what Nikon DSLR you're using... but they all are either full frame (1.0X) or APS-C (1.5X) sensor format.
The Olympus "micro Four/Thirds" sensor format is a bit smaller than APS-C... with a 2X lens factor. So, in effect that 70-300mm on it would behave "like a 140-600mm" on a full frame camera.
The bridge camera you mention uses a 1" sensor, which is even smaller still. It's actually large for a sensor in a non-interchangeable lens camera... but still not as big as the DSLRs or Oly use. It has a 2.7X lens factor. Bridge and other non-interchangeable lens digital often don't even talk about their actual focal length, but use "35mm film" comparatives. This is now they manage to have some incredible telephoto claims... smaller sensors make modest focal lengths "act" a whole lot "longer". I don't know what they claim about the Sony, but you probably will need to compare to the "140-600mm" mentioned above. In order to have the same angle of view as a 600mm lens on a full frame camera, 400mm on an APS-C, or 300mm lens on an m4/3... a camera with a 1" sensor will need a lens with an
actual focal length of about 220mm.
A major difference with smaller sensors is low light/high ISO limitations. There are cameras around 20MP with sensors in all four sensor formats: full frame, APS-C, m4/3 and 1". In full frame, this makes for a very "uncrowded" sensor and the latest of these have pretty incredible high ISO, low light capabilities. Some now have usable ISO ranges at and above 104200. The smaller APS-C format has benefited from this too, though a 20MP sensor in that size is far more crowded. Some recent APS-C models have usable ISO as high as 12800 and even 25600. m4/3 are a little less than that, since their sensors are a bit more crowded. You'll find an even smaller 1" sensor with 20MP resolution will be more limited. I don't have any cameras using m4/3 or 1" format and haven't studied them all that closely, but I'd be surprised if 1" could make images without too much noise much above ISO 1600 or maybe 3200. Even so, that would be a lot better than a few years ago, when smaller sensor digital cameras were limited to about ISO 400 or less, even with lower resolution (and some of the really small sensors still are pretty limited... you might be able to select a higher ISO, but won't like the results).
The other consideration with smaller sensors is control over depth of field. DoF doesn't actually change directly due to sensor size alone. However, because the actual lens focal lengths they use are much shorter, they tend to render deeper DoF. If you are wanting to isolate a subject using a shallow DoF, heavily blurring down the background behind them, it is difficult to do so with the smaller sensor cameras. Olympus (and to an extent their partner in the m4/3 format: Panasonic), offer some lenses that feature a larger than usual aperture in an effort to offset this... say an f/2.0 instead of an f/2.8. But in the even smaller format you won't find this same effort being made. Partly that's because a lens with an extra large aperture needs to be bigger diameter, as well as some other optical considerations. If, on the other hand, you are looking for extra DoF.... images that are sharper from near to far, the smaller sensors can have an advantage.
However, with really small apertures comes another problem: diffraction. This is an optical effect that robs images of some of their fine detail, the smaller the aperture the greater the loss of image quality. Due to the scaled down size of the non-interchangeable lens cameras with their smaller sensors and shorter actual focal lengths, a truly small aperture can be a problem. Part of this has to do with how much enlargement is required, to make any given size of print from an image with the different sensor formats. For example, to make an 8x12" print from a full frame camera with a relatively uncropped image means approx. 8X magnification. The same print from an APS-C camera is roughly 13X magnification. As a result, full frame "tolerates" about one stop smaller apertures than APS-C before diffraction becomes a problem, since the FF image is less enlarged. I haven't done the math, but I'd anticipate that a still smaller m4/3 will be roughly another stop "limited", and an even smaller 1" sensor will around two stops. For example, around 20MP an 8x12" print just barely starts to show some effect from diffraction at f/11, while an APS-C it's around f/8. An m4/3 like Oly uses might be around f/5.6 and a 1" sensor such as is in that Sony you mention, f/4. Now, at these settings diffraction is minor... just getting started.... but as you decrease the size of the apertures even farther, you'll seen increased diffraction with each smaller f-stop. I try to not use smaller than f/16 or... maybe... f/22 with full frame, f/11 or f/16 with APS-C. There's some effect from diffraction, but it's still fairly minimal. I avoid f/22 with APS-C cameras and f/32 or smaller with full frame. I don't have any m4/3 or 1" sensor cameras, but if I did I'd probably limit them to around f/11 and f/8, respectively, avoiding f/16 or smaller with m4/3 and f/11 and smaller with 1". It might not be quite that much, since the step from APS-C to m4/3 isn't all that large.... but I'm rounding things off in full stops for purpose of discussion here.
Taken all together, this means that the smaller the sensor format, the less "flexible" your range of available apertures... As you can see from the above, there are some limitations at both extremes: large apertures to make for shallow DoF effects, and small apertures to render things sharp from near to far. And that translates into less control over how DoF is rendered.
Those are some of the things you need to weigh, when comparing the different formats.