guyfawkes: Reading many comments about "equivalence" both here and posted elsewhere, there does seem to me to be one question I'd like to ask: what practical applications are there that one would need to know this?
For example, if one owns a FF sensor dslr, does one really need to know what the so-called equivalence is for DoF for another format? Or turn this around. Would anyone moving from an APS-C system to FF need to know? How on earth would this impact on images they proposed taking?
In my days with film, using anything from sub-min up to 5x4, equivalence never even entered the equation. Photographers simply worked within and knew how to use the tools they used. So why has it assumed a proportion totally out of kilter with its importance now we use digital cameras?
It very much smacks of pseudo science to me.
Because FOV is exactly measurable. OTOH, sharpness and noise are subjective qualities.
MarkByland: What about the misleading terminology of "getting more reach"? After working in two different camera shops, I've heard a lot of customers use this misnomer when referring to 4/3 sensors. Claiming that some how a lens of, say, 100mm focal length will some how bring them closer to the subject. This is wrong. I've often thought that instead of the phrase "Crop Factor", it should be called "Field of View Crop." Because that's exactly what it is. The focal length of the lens doesn't change when it's on a camera of different sensor size. The focal point of the lens does not change. Ultimately, you just see less of the field of view which leads people to believe that they are some how magically getting more distance or "reach" out of a lens. Entirely untrue. Due to the nature of a smaller sensor, you just see less of the FOV in front of the camera given the same focal length lens that was not designed for equivalency.
You are correct w r t lens and FOV. But usually smaller sensors have a higher resolution than the corresponding crop of an FF camera. So it's not a simple crop, really.
Well, I am not the least concerned to have GreatBustard the last word. My response was directed to Mr Butler, anyway.
The type of noise dependend on sensor size is shot/photon noise. It is dominant in the lighter parts of an image. Most people do not find noise in the lighter parts of an image as disturbing as noise in the darker parts. The noise in the darker parts is mostly caused by read noise which depends on the electronic camera components but has nothing to do with sensor size. Now also ISOless cameras are appearing, meaning the read noise remains constant regardless of the camera's ISO-setting, rendering 'equivalent ISO' meaningless as far as read noise is concerned.
Apart from the fact that smaller sensors are mostly more efficient, they usually also have a higher resolution than larger sensors. When downsampled to an 'equivalent resolution' (that of the corresponding FF crop), noise will be reduced.
Noise is also a subjective quality and the type of the noise is a very important.Most people find color/chroma- and pattern noise more disturbing than luminance- and random noise. Thus an FF camera with a lot of chroma noise and banding will have worse noise than a crop-sensor camera at the same ISO setting and with many times stronger noise - provided it's only luminance noise and randomly distributed.
The use of 'equivalent f-number' by itself is a gross simplification. When it is used, all relevant parameters and preconditions should be explicitly specified.Just quoting the results of a web-based DOF calculator is not sufficient and rather unprofessional. Even if it has implemented the correct formulas in a correct way and it uses correct sensor data, the formulas themselves assume for example that the lenses are free of aberrations and that diffraction is nonexistent. Demosaicing is ignored.
Depth of field is about the sharpness in a certain area of the photo. Sharpness is a subjective quality and can hardly be put in numbers. Furthermore, sharpness/DOF depends on focus, filters, subject movement, sensor- and lens resolution, modulation transfer, diffraction, aberrations, anti-aliasing filter, demosaicing, camera stabilization, steadyness of the shooter, acutance, noise reduction, display/print-size and illumination, viewing distance and the observer's visual acuity.
DirkL: Pseudo scientific mumbo jumbo. That smaller sensors are more prone to noise and have more DOF has been known for years, even for informed consumers.
If you try to quantify this with formulas, and then promote these to help the consumers, then make sure that
a) the formulas hold water and are appliable to the camera the consumer is interested in. But except for FOV you will never be able to do that, there are too many parameters to consider (different sensor-, lens- and processor technologies).
b) shallow DOF and high-ISO shots in low light are of equal importance to the consumer as FOV.
Otherwise you will only add confusion and desinformation, doing the consumer a disservice.Keep testing instead, data is the only reliable way to compare cameras.
This for example is pseudo scientific:"for same generation""(at least)""dependent on""personally I think"
Pseudo scientific mumbo jumbo. That smaller sensors are more prone to noise and have more DOF has been known for years, even for informed consumers.
boyd2: Again NO DECENT OPTICAL VIEWFINDER!@$% And this should appeal to DSLR owners? Forget it Canon ...
"I honestly think there would be less complaints if Canon didn't even include an OVF at all. In fact many would welcome the size reduction."
In this I agree. The OVF is worthless if it is the same as in the G12. Either ommit it and make the body smaller, or put in a decent optical, hybrid or fully electronic VF.
The Nikon CSC makes sense. Nikon DSLR users looking for a compact second system will look into it, as well as P&S upgraders, in the latter case the Nikon brand and marketing will give some extra help over m4/3.
For me, as a m4/3 user, it is not worth to consider at the moment though. Inherently, the larger m4/3 sensor has a better IQ as well and the m4/3 lens lineup is much larger. I especially miss fast glass which would compensate for the smaller sensor in the Nikon CSC system.
But I will definitely be watching what Nikon and others will do in the CSC field in the years to come.