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Discussion in 'Digital Photography' started by pdechavez, Aug 24, 2008.
Aside from the cropping of 1.5x of the APS-C and 1.3 on the APS-H, what other differences are there?
lower pixel density/larger pixels = less noise
Shallower depth of field
Among other differences, with a full frame sensor, you can get more shallow depth of field for a given focal length and aperture. With focal length and aperture held constant, the closer the camera is to the subject, the shallower the depth of field; the further, the deeper.
With a full frame sensor, you have to move closer to the subject to fill the frame than you would a crop sensor. Thus, less depth of field. This is an advantage for many types of photography, such as portrait, where you want a background blur. When people, accustomed to digital point-and-shoot cameras, see portraits taken with a DSLR, one of the first things they notice is the background blur (called bokeh), since it's just about impossible to achieve that effect with the tiny sensor on a P&S.
Of course, an APS-C and APS-H sensor can also provide very pleasing bokeh, but the affect is more profound as the sensor size increases.
There is another difference, but it is probably too subjective to be mentioned by most reviewers. In a nutshell, those who own both FF and Crop sensor cameras often mention that their FF images are subjectively superior, with more "pop", which I interpret to mean better (a) contrast, (b) per-pixel sharpness, (c) detail, and (d) tonal range or shades of a color.
A rough analogy might be between mass-market sound systems and audiophile-grade sound systems. Both play the same music (i.e. capture the same light), but the audiophile sound systems are over-engineered to eliminate internal sources of noise, increase dynamic range, and improve transient response.
Some people will not hear the difference, but others will.
With a FF sensor you should have much more leniency shooting at higher ISOs. Think of a point and shoot camera that has 12mp. Sounds nice right? Sure, but the smaller the sensor + more megapixels = way more noise.
For a given number of pixels (e.g. 12MP in APS versus full-frame), full-frame's larger pixels will be more forgiving of small (and I do mean *small*) amounts of camera movement during exposure.
Sensor-based diffraction won't hit as early on full-frame, again because of larger pixel size. So, for example, with my D700 I might have to think about this starting at f/16, where a D300 shooter might have to think about it at f/11 or f/13.
Full frame and APS both have plusses and minuses when it comes to lenses. Light hitting the APS sensor mainly comes through the center part of the lens - the "sweet spot" - and not the edges (advantage). However this also means that lens imperfections in that "sweet spot" can have a disproportionately greater effect on an APS sensor's end image (disadvantage). I'd say overall it's usually an advantage for APS - but I have read reviews of lenses that are mediocre on APS but good on full frame. As a side note: I've read reviews of lenses that are stellar on film, but apparently not-so-much on full frame digital!
One downside to full-frame is going to be size and weight, whether it be the camera or the lenses.
Ding ding ding!
Shallower depth of field at a given level of magnification (field of view) and aperture is the most fundamental (as in unchangeable) difference between small and large sensors. As sensor technology improves, resolution and light sensitivity might improve, noise might be reduced, etc. but it is physically impossible to get the same shallow depth of field (and thus subject isolation) at a given magnification factor and f/stop on an APS camera vs. a full-frame camera. This is a limitation of optical physics, not one that can be overcome with a new and improved sensor.
Note that depth of field is the same at the same real focal length and aperture on any camera. A 200mm lens at f/4 has the same DoF on an full-frame body and an APS-C body - but on the APS-C sensor, the image is cropped by the smaller sensor. A 320mm lens at f/4 on the full-frame body would fill the sensor with the same apparent view as the APS-C sensor at 200mm, but with a considerably shorted depth of field.
Note quite true. Depth of field is derived from: the lens focal length, the aperture, the distance from the subject, and the circle of the confusion. The last item is based on the sensor size. All Canon 1.6x cameras have the same CoC; all Nikon, Sony, etc. 1.5x cameras have a common CoC; and all full-frame 35mm cameras have another CoC in common with each other. The larger the CoC, the shallower the depth of field, provided all other variables are the same. The larger the sensor (or film), the larger the CoC.
Couple the larger CoC value of a full-frame camera with the fact that a full frame shooter will need to stand closer to the subject to fill the frame the same as a crop shooter (the shorter the subject distance, the shorter the DoF). Or, as in your example, keep the subject distance the same, but use a longer focal length. The affect is the same.
My understanding is that the APS-C and full-frame sensors are the exact same distance from the rear element of a given lens, which would make the circle of confusion projected on the sensor from a given point source identical in diameter. (It would just cover a greater proportion of the APS sensor). Just because a 200mm lens is cropped to the field of view of a 300 or 320mm lens on an APS sensor doesn't make the circle of confusion smaller.
Edit: I think we're saying the same thing - when I say "real focal length" I mean the actual, optical focal length, not some frame-filling "equivalent" focal length.
People can see the difference right away between a full frame sensor and a 1.5x cropped sensor but 1.3 and 1.5 are very close.
I'd expect that you'd see slight differences in the preferred camera to subject distances and depth of field but again 1.5 is close to 1.3
This is the primary distance.
Also note that astigmatism, coma, field curvature, chromatic, and all other 3rd order and higher aberrations (except spherical) are "field dependent" which means that they get worse the further from the center you go. Full frame cameras fill the frame with image produced by the edges of the field, so for all lenses (including L, DO, etc.) the image is going to be worse on the edge of a full frame sensor than a cropped sensor in general. Therefore full frame sensors are extremely sensitive to the quality of the lens used