Frosty Loc: Minnesota

Being new to digital photography, I have a lot of questions. One of which is, what is the relationship between sensor size and megapixels? For example, If two cameras had the same lens, the same number of MPs and the same type of sensor, but one had a larger sensor, what would the one with the larger sensor do that the other would not do and why? Would there be any noticeable difference in the finished product?

Second question, is there a relationship or rule of thumb that one can use to determine how large an acceptable print can made based on number of MPs? For example can I determine how large an acceptable print can be made from a 10 MP camera vs a 16 Mp camera?

Thanks ahead for any clarification on these topics.

Frosty

profpb Loc: Venice, Florida

You are beginning a journey. No one ever gets there. Enjoy the trip but there are no short cuts or simple answers.
Q1. Sensor size matters. Larger sensors means more megapixels. Full frame is the recent target for digital as opposed to "cropped" sensors which are smaller. The largest Nikon has 36+ MP. 24MP is close.
Q2. Yes and Yes. Printing is limited by the information available. More information (MP) results in higher quality for larger prints. My software lets me view the number of pixels for the print dimensions of height and width and converts those measurements to inches.

This is a brief start; now buy the book, take the classes, join the websites, but don't forget to take some pictures.
Just remember it's a journey and for all of us there is no end. ~the professor

mikemilton

Hi!, Welcome.

Here is one take on minimum resolutions for prints:
http://help.smugmug.com/customer/portal/articles/93359

Note that it it listed as dimensions rather than megapixels but you can just multiply the two numbers if you really want megapixels.

As to your other question, no, there isn't a direct relationship because the pixel pitch varies from sensor to sensor. That means that the size of the individual photosites can range quite a bit so smaller sensors can actually have more sites than larger ones.

If a camera had a larger sensor but the same number of photosites then it is likely that it will have greater dynamic range and/or less noise. Again this is not strictly true as there are other design issues that can minimize this effect. For example, the sensitive bit of a pixel is smaller than the size of the photosite and has a lens over it. The lens can be gapless (meaning it covers the whole site and focuses the light on the sensitive area there may also be spacing between these lenses.) Also there is a colour filter which can pass more or less light.

GrahamS Loc: Hertfordshire, U.K

Frosty, question 1: you will find it all here:
http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm

Q2: The accepted print resolution for high quality prints today is 300 pixels per inch. This can be reduced according to the viewing distance, to as low as 180 ppi for a large poster viewed at more than 8 feet distance. This chart from B&H may help you understand:

http://www.bhphotovideo.com/FrameWork/charts/resolutionChartPopup.html

Frosty Loc: Minnesota

WOW! Thanks to all of you for the in depth replies. I thought there would be fairly simply answers but I guess not. I thought about this when people on the forum were talking about full frame sensors vs 4/3, or whatever. I think most people, including myself thought simply that the more pixels the better and that was that. If that was the case then a small PS with 18 MP should be as good as a DSLR with !8 MP. That did not seem right. As profpb said, "enjoy the journey", Well I am, thanks to folks like you and this forum.

Tea8 Loc: Where the wind comes sweeping down the plain.

You are right the answers are a lot more complex than you think. I was a lot like you when I started to dig deeper into the realm of photography. I couldn't quite understand it all and then I happened upon this place and have been hooked ever since.

Oh and the reason that so many people believe that MP's are the most important thing is because thats what the camera sales people want you to think. Have you ever watched HSN or QVC when they have cameras up for sale? What are they always talking about? LOOK HOW MANY MP's THIS CAMERA HAS!! IT'S SO WONDERFUL!! LOOK AT HOW CLOSE YOU CAN GET IN WITH IT!!(They want consumers to believe that it's the most important thing so that when they come out with a newer model in a year or so the people will go, "Oh, great now my camera is outdated and I can't good pictures anymore. I better buy this new one with 2 more MP's so I can get the best photos." )

mikemilton

Ah megapixel obsession... I started out (in DSLRs anyway) with the original Canon DSLR (a bit over 3MP) and it was a bit confining. You sure did not want to crop but quite serviceable. I've had a few since then. I was happy ar 6, delighted at 10-12 and found that the 5DmII overkill (from that perspective, hated the camera for other reasons).

I'm at 18 now and that is perfect for me. I'm not going to print bigger, have a little wiggle room for cropping and am really happy with the image quality.

marcomarks Loc: Ft. Myers, FL

I have to disagree with your Q1 answer. Larger sensor does NOT automatically mean more megapixels. I have a Canon A2200 P&S with a tiny sensor sitting here that is 14.1 MP. I also have a Panasonic Lumix with the same tiny sensor size that has 12MP. My Sony dSLR has 16.2MP on it's crop sensor but there are other dSLRs that have anywhere from 8MP to 24MP jammed onto the same size sensor. Megapixel rating of a sensor is determined by the size of the pixels, not the size of the sensor itself.

A full frame sensor has a better quality picture partially because the pixels can be larger while also retaining a high quantity of of them.

GrahamS Loc: Hertfordshire, U.K

It's all about Pixel Pitch and amplification noise.

Frosty Loc: Minnesota

GrahamS - Thank you very much for the links to the web sites that explain how this all works.

As I understand it from the BH web site, summarizing from both links:

A small number of MPs (10 or slightly above) in a large sensor is preferred because the larger pixels gather more light which results in greater dynamic range and less noise but still has enough pixels to produce photo quality large prints (up to at least 20 x 30, according to the chart).

Sound right?

boshon1

Pixel size is more important than number of pixels for many reasons.

GrahamS Loc: Hertfordshire, U.K

Right on! Which is why a Nikon D700 produces such high image quality. Only yesterday I was looking at a double page spread in a pro photo magazine that was taken with a D700 and it was superb.

PhotoArtsLA Loc: Boynton Beach

Sensor size has a lot to do with the issue of depth of field, for tiny sensors, like they have on many digital video cameras, the 0.25" sensors often used negate creative use of focus short of attaching a cinema adapter to it. It has to do with the ways a lens must be designed for the tiny format, which tends towards universal focus.

The larger the sensor, the more you can count on being able to shoot creatively regarding selective focus.

By the time you are talking DX or FX, you are talking top quality. I have blown up a DX frame to 4x6 FEET for a trade show, and it was stunning.