Too many megapixels? Six is enough for an 8x10.

Started Apr 26, 2009 | Discussions thread
Anastigmat Forum Pro • Posts: 12,664
Re: Too many megapixels? Six is enough for an 8x10.

bobn2 wrote:

So we'll pitch your view about the 'tones' against quantitative
measurements taken by experts and the subjective opinions of may
professional photographers. Right.

Pros are unlikely to use the D40, so they are also unlikely to have an opinion about it. Besides, many pros are just as ignorant about photo equipment as you or I.

There is
a debate about whether down-rez of a higher megapixel camera can
replicate the quality of the lower one--there's an article on DP
Review that says it can't--

In a deeply flawed article that was immediately discredited. But
since Phil Askey can never be wrong, he didn't have the courtesy
either to discuss its failings with his critics or to pull the
article. It just sits there, continuing to misinform the gullible.

I wonder who are the gullible.... Those who keep upgrading to new cameras with more but smaller pixels thinking that they will get better image quality because of the increased pixel count. Of course, there are definitely enough of these consumers to keep the upgrade market busy and healthy.

Where is the extra money spent? Moreover, a 15 or 24 MP image
properly downsampled to 6MP is better in virtually every respect than
a native 6MP image, with higher high spatial frequency contrast and
potentially better noise control, in that the additional information
can provide for smarter NR algorithms.

So, you pay oodles of money for a 15-24mp sensor, so you can downsample it to match the quality of a 6mp sensor? Why not save the money and use it for something better? I am not against higher resolution, but not at the expense of increased noise. Besides, downsampling is not easy:

'Before answering the question in detail of "does it work and how well" (yes it does, and very well) we need to understand that "binning" has been done before, but rarely with a colour matrix sensor and never very well. Monochrome sensors have been binned, but doing so with a Bayer matrix is a monumentally more difficult task because each adjacent pixel is of a different colour and has a quite different spectral response. Also, because binning reduces resolution by a factor of four, it really doesn't make a lot of practical sense to attempt unless and until one has a sensor such as the one in the P65+, with 60 megapixels unbinned. The resulting 15 megapixel binned size is bigger than many pro DSLRs, such as the Nikon D3 and D700, and therefore quite usable for many commercial applications.'

MF backs have bigger sensors. Bigger sensors have more DR, whatever
the pixel size. You have made the very common mistake of attributing
the effect of sensor size to pixel size. In any case, MF is dying as
we speak. So much for the market.

Bigger sensors allow the individual pixels to be big even though there are many of them. It is the big individual pixels that can detect a weak signal (while at the same time retain the ability to record a strong signal without the signal clipping) that allows big sensors to have good dynamic range. Cram a lot of tiny pixels onto a medium format sensor, and you would get low dynamic range. Further, medium format is not dying. Sales has slowed, and will get worse because of the slow economy, but new products are being introduced. Leica and Pentax are planning new medium format cameras.

Zero logical argument and very poor choice of 'experts'. Why would
you choose the opinion of a web developer over the fellow who
invented the active pixel sensor?

Just because others disagree with you does not mean that their arguments are not logical.

I think Daniel Browning made a pretty good fist of the arguments.
There are many, many detailed threads which go through all the
arguments, here and elsewhere. When people post bogus facts without
supporting evidence, I think it's their responsibility to back up
what they say, not the person who disputes it.
The problem is, that their whole position is based on two basic flaws:
i) making assessments at the pixel rather than image level.

Images are built up by individual pixels. Look at a newspaper image. The individual pixels are awful in quality. That is why you don't get a good image from the page of a newspaper. Look at a magazine page, the images are much better because the individual pixels making up that image are better than those found on a newspaper. You cannot separate pixel qualiity from image quality. Pixels are the ingredients of an image. Bad ingredients will not a good image make.

ii) Doing theoretical assessments at the pixel level and failing to
analyze the way in which pixels aggregate to form an image.

How do they "aggregate" except by being placed next to each other. One pixel should not bleed its signal to its adjacent pixel. Pixels do not mix. A good image depends on each pixel maintaining its integrity and its goodness. If you start out with inferior individual pixels, you will end up with an inferior image.

All the people capable of rational discussion abandoned the 'small
pixels bad' position long ago. the ones who are left are incapable of
moving past this stage.

-- hide signature --


Small pixels are not necessarily bad. However, if they get too small so that the signal becomes too weak, then the S/N ratio will become too low for good dynamic range and good image quality. Noise also becomes a problem. The D90 relies on strong doses of noise reduction at ISO 400 and above to keep noise down. OTOH, the D40's Sony sensor is well known to be practically noise free at ISO 400. NR is only needed at ISO 1600 and above in the D40. Alas, to get the D40's better sensor, you have to put up with an inferior camera body. To get the D90's better camera body, you would have to accept a noisier sensor. That is life. It is full of compromises.

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