Is there an optimal ratio of sensor area to Mp area on that sensor for optimal IQ?

[Sudhakar Redddy]

This question appears more relevant now that Nikon has come up with its new entry level DSLR D3200 with 24 MP. Its earlier model D3100 has 14 MP & the sensor size of both these cameras is almost the same:

Nikon D3100 = (23.1 X 15.4 mm) Sensor size ----> 14.2 megapixels
Nikon D3200 = (23.2 X 15.4 mm) Sensor size ----> 24.2 megapixels

Sample images of D3200 show somewhat inferior in detail & color rendition compared to the IQ of D3100 though it may be a purely subjective feeling.

[ScottL]

IMO, this is Nikon's way of marketing to the world of MPs are more important than quality. I say this because the market for the D3100 and D3200 is more towards parents that want a DSLR but dont want to over spend and are hooked on the "My camera has more MPs than your camera" attitude.

I do not know the absolute science behind it, but I would believe that the image quality degrades with each pixel you shove onto the same size sensor. Now you have twice the amount of pixels fighting for the same space, sharing and increasing the heat generated, etc...

This is all why I tell many people that when it comes to point and shoot cameras not to go MP crazy... It is not necessary and will only take up more room on a computer to store... It is unfortunate how many people are nieve and don't realize that to make a 4x6, 5x7 and even 8x10 print, there is no need to buy 14, 16, 18, 20MP cameras.

DISCLAIMER: To anyone on this forum that owns the D3000, D3100, D3200, etc... This is not in any way saying anything bad about the cameras. I am simply stating who this series of cameras is marketed towards due to the ease of use and price of kit.

[Cadwell]

Is there an optimal ratio of sensor area to Mp area on that sensor for optimal IQ?

The short answer to this is "no, there isn't".

The reason behind that answer being, "not all sensors of the same size are equal". Since the inception of digital SLR technology there have been great advances in the technology of the sensors themselves. These advances have led to massive improvements in the levels of digital "noise" produced in images. As an example, a Canon EOS 1D with only four megapixels to its name is hugely out-performed by the much later EOS 1D Mark IV at 15MP on the same sensor size.

Whilst digital photography technology is starting to mature, it would be a step too far to suggest that we have reached the final stage of sensor development.

The proper answer to the original question of "Is there an optimal ratio of sensor area to Mp area on that sensor for optimal IQ?" is probably,

"Yes, for a given sensor base design and generation there is, but such comparisons are invalid between sensor designs and generations".

[joshimode]

With today's technology, the number of megapixels that can be crammed into a relatively small sensor is high. With micro lens and newer processors, the megapixels can be increased but then photography in low light could be noisy when using a higher megapixel sensor when sensor size is same.

These days the limiting factor with a entry level camera is still the quality of the kit lens. The kit lens doesn't have the resolving power to fully do justice to the higher megapixels. For anything more than 16 megapixels or 18 megapixels, i guess you need high end lens.

In few more years if the megapixel war keeps continuing, the current batch of high end lens could be found wanting. This i say so with whatever little i have come to hear from different experts. Others plz correct me, if iam wrong.

[Cadwell]

Certainly as sensor resolution increases some flaws in a lens' performance will become more apparent. Chromatic aberration that was only one pixel wide when viewed at 100% might become two pixels wide, for example.

However, how much of a problems is this in reality? Images are rarely used at 100% pixel size. An image printed at 15x10" will look pretty much the same when taken using an 8, 15, or 20 megapixel camera when using the same lens. In fact, in a blind test, I'd be surprised if many people could tell which was which.

As an example, I was recently a little concerned when approached by a customer about using a particular image on a large banner advertising an event. Oh, the shot was sharp enough and taken with one of my better lenses but it was an old photo shot using my EOS 1D Mark II - an 8 megapixel camera. Of even more concern was that the image was a slight crop so the number of active pixels was probably more in the 6 or 7 megapixel range. I needn't have been concerned. I have seen the resulting banners, they show the athlete at about life size and they look great, even when viewed close up.

To be perfectly honest, once you get beyond about 8 megapixels, for most practical purposes you're into advertising gimmick territory.

However, for reasons I don't pretend to understand, cameras with larger photosites seem to produce images with more "pop" and vibrancy than those which use smaller photosites. Rather than trying to cram ever increasing numbers of photosites onto a sensor, perhaps camera manufacturers should concentrate on placing fewer, higher quality ones in the same area.

[joshimode]

You are right Cadwell. Anything more than 8 MP is more than sufficient for normal size of printing one undertakes. But more megapixels is useful so that even after a crop the print size can be considerably big.

Regarding posters, the distance of viewing also comes into play. If you are viewing it from a distance which is thrice its diagonal length, one cannot distinguish individual pixels. Its a different matter if the poster is close enough and your camera's pixel count is less.

We hardly take any prints which is more than a feet long. For this, the lowest resolution cameras available today is still an overkill. The difference in print resolution of 300dpi or 240dpi is hardly noticeable, unless you are a pixel peeper. At 240dpi the base camera model available today can print atleast a feet across.

So, one should have to draw a line to this megapixel race, which hardly seems to finish anytime soon.