Merits of APS sensor

People are really confused about equivalence. If you want to take the same photo from the same perspective with two different sensor sizes you will need to change the focal length to get the same FOV. That's why we talk about "equivalent field of view".

Also, arguments about how handy the Q is because it can be in your pocket are beside the point. I too find a smaller camera handy, which is why I shoot with an Olympus PEN. This has nothing to do with which sensor is better.

I also don't know why Landscapes and a huge DOF are synonymous? Here's an example by Womble that has real depth.

https://www.pentaxuser.com/forum/topic/lens-shootout--pentax-prime-lenses-50-55mm-39381/p-1#comm441952

This is academic. Surely what counts is how a camera behaves in use. This is a shot I took with a Q:

link

I couldn't have got such DoF (the rain on the window and the subject in focus) on an FF or APS-C camera without stopping down to a point that would have made it impractical. I know FF cameras can be used with cropped sensors and APS-C lenses, but they cannot -as far as I am aware - replicate the extended DoF of compact sensors.

Generally speaking larger sensors will give better results. And I also mostly prefer the reduced DoF obtainable on larger sensors. But on occasion - the street at night for example - the heightened DoF of a compact sensor can make it the preferred tool.

It had never occurred to me that shot was with the Q Andrew, great stuff. The larger dof is great for candids as there is much more chance of getting the subject in focus.

I may be out of date, but last time I looked (no more than a few months ago) the highest density FF sensor available in a current model camera was the Nikon D800's 36 megapixel monster. If you take an image from that sensor and you crop it down to the size of the sensor on the Pentax Q you will be left with (approximately) a 1.2 megapixel image.

Now arguments about resolution and image noise etc. notwithstanding, I'm willing to bet that if you printed both images at A4 size, the one taken with the Q (12 megapixels) would look a hell of a lot better. The cropped D800 image would probably look like you built it out of Lego bricks.

It's hardly the same net effect.

That's not an advantage of a smaller sensor it's an advantage of having a higher pixel density.

How many Megapixels would the D800's sensor have if it had the same density as that of the Q ?

Around 360 megapixels, roughly.

In a way, however, it is an advantage of a smaller sensor. This has to do with imperfections in the manufacturing process. Manufacturing a 360 megapixel FF sensor is impractical because at such high densities the rate of flaws is such that practically every unit you produced would be defective. By reducing the size of the sensor the number of defective units is reduced to an acceptable level.

The sensors are manufactured on a big 'slice'. Think of it as being a bit like cutting little squares out of a large slice of swiss cheese (the kind with holes, of course). If you cut out largish squares, say twice the size of a postage stamp, pretty much every one will have a hole in it somewhere. However if you cut out tiny little squares you will get a far higher proportion of hole-free pieces.

So you could say that higher pixel density is in itself an advantage of smaller sensors, at least with current manufacturing processes. This may change as better manufacturing techniques emerge.

...Expanding on the above my problem with the whole 'there is no advantage to smaller sensors' argument is that it only works when reduced to a purely theoretical level. For example, to requote the words I quoted earlier:

This is absolutely true in theory, no arguments there. But so long as the larger sensor with sufficiently high pixel density to achieve this doesn't exist, the theory is of no help whatsoever to an actual photographer using actual equipment to take actual photographs.

In real life, here and now, to a photographer in the field, the advantages of smaller sensors which have come up in this thread are perfectly genuine.

When taking wildlife photographs the limiting factor is often how close you can get, the focal length of the camera and the number of pixels that you have.

To double the image size you can;

* Halve the distance that you take the picture at
* Double the focal length of the lens
* Quadruple the number of pixels the sensor has for any given size of sensor and then crop.

The depth of field does not change for a given lens, with a given aperture. However beacuse you need a shorter focal length to fill the frame, with a smaller sensor, you get a bigger depth of field unless you open the aperture up.

I would agree with this, and point out just in case it wasn't staringly obvious that quadrupling the number of pixels on your sensor is not a practical option unless you possess a magic wand - especially if you already have the highest density sensor available for its size (say a D800).

And what does quadrupling the pixels do for noise? That is if it were possible. That is the case for the bigger size sensor.

This site pretty much says it all:

http://www.mdavid.com.au/photography/apscversusfullframe.shtml

A good photo by the way.

Best regards