6 megapixels vs 8 megapixels

[eac706]

What print size one (human eye) can actualy see the differnce between a 6megapixels and 8megapixels camera assuming using the same lens/exposure/iso etc.?

Also what does a 35mm camera resolution compare to DSLR megapixels?

[drisley]

I've printed images from my 300D (6mp) and 20D (8mp) and I don't really see any difference even at 8x10.

[mdr]

Also what does a 35mm camera resolution compare to DSLR megapixels?
That depends on the film you're using. The grain of the film is not visible from Fuji Velvia 50 scanned on my Nikon V without grain desolver. This gives the equivalent of about 21mp.

I have read somewhere that with higher resolution scanners the grain of Velvia 50 becomes visible at about 40mp. And that's without using any grain desolvers, which you could see as the equivalent of sharpening algortihms in camera or with the computer. So in terms of pixel count, DSLR's are still way off.

For pure quality, I would still go with my EOS 3 and Velvia 50, but scanning takes a hell of a lot of time :( . As I print mostly at 12x8, the 20D's 8mp gives me the same output quality without the hassle and effort of developing and scanning E6 :). And that's not even mentioning the that digital film after the initial outlay is cheap :D.

[Monito]

Megapixels measure area. Print dimensions are linear. So take the square root of the ratio to get the linear ratio. 8/6 = 1.33. The square root of that is 1.15. So the bigger resolution will give you a 15 percent wider picture.

[Belmondo]

Megapixels measure area. Print dimensions are linear. So take the square root of the ratio to get the linear ratio. 8/6 = 1.33. The square root of that is 1.15. So the bigger resolution will give you a 15 percent wider picture.

That's a difficult concept for some people to get around. A picture with twice the resolution is only a hair over 41% wider/taller.

[mdr]

The wole area of mp, ppi and dpi is a minefield, especially to the novice. Even the manufacturers cannot get this right in their product specifications.

What is important though, is that if you print a picture, the number of mp's in the original could affect the picture quality depending on the output size. My rule of thumb is, that as long as the number of mp's imply a print resolution of 300dpi or higher, then the output quality will not differ to the naked eye.

[CyberDyneSystems]

All I can say is that I have printed 20D, 1D MkII, and 10D images as large as 13"X19" and I can see very little improvement in the 8MP images over the 10D's 6MP....

I feel that both file sizes can be used to print larger than 13"X19" with no problem at all.

[Jim_T]

The 'rule of thumb' for quality prints is to print at 300 pixels per inch (AKA dots per inch). In reality, you can go lower.. (ie 250 DPI)... How low you go depends on personal preference and how critical your eye is.

Consider:

Canon 6MP images are usually 3072 pixels across

Canon 8MP images are usually 3504 pixels across.

Printing these images at 300 DPI will result in the following print widths:

6MP.... 3072 pixels / 300 dpi = 10.24 inches

8MP.... 3502 pixels / 300 dpi = 11.68 inches

At exactly the same resolution, an 8MP camera will allow you to print 1.44 inches wider..

[iwatkins]

And the flipside of all this is that a 6MP image is quicker to process though Photoshop etc. and takes less space on card and disk. ;)

I always try to print at 300dpi or higher. saying that I had some images that were 300dpi and 6x4, and JPEGs at that, and had them printed by Ofoto.com as 12x8 with no processing on their part, i.e. equivelent of printing at 150dpi.

Print quality is still excellent at normal viewing distances (hand held). It actually suprised me to be honest. OK, I know these big labs use continous tone printers, but even so, it still suprised me. So much so, that I wil probably upload all my pictures for printing at around 200dpi for the size I want instead of pushing hard for 300dpi+

Cheers

Ian

[eac706]

I would to thank all for your kind help. Being an EOS 5 user going to DSLR. Since the 20D is a bit to tight to my buget and the 300D features do fine for me because I mainly use the appature/shutter priority and my most concern was will I be dissapionted from 35mm and was it worth the extra money for an extra 2 megapixels.

[Andy_T]

EAC,

I agree with you, the 2 MP difference is not that important.

However, coming from an EOS 5, you should definitely go to a photography shop and pick up both bodies and compare them.

It's true, the 300D is a great bargain and a very capable camera, but do not underestimate the 'look and feel' of the camera. If you like it, then it's very fine, if you are not so happy with it, you might also look at a used 10D.

Best regards,
Andy

[tim]

I've had my 300D for 4 months now, and i've just upgraded to the 20D (it arrives today). You should look carefully at the features, and at yourself, and decide if you think you'll get upgrade envy in the next 6 months. If you think you might, get the 20D.

The 300D sucessor will be released very soon, in Feb at the big show that's coming up. It will have the resolution of the 20D, but with the current rebates it will likely cost more. If you want a good camera for a great price get the 300D now, if you want a better camera for a bit more wait. That's assuming you don't go for the 20D.

[Jesper]

That's a difficult concept for some people to get around. A picture with twice the resolution is only a hair over 41% wider/taller.
Belmondo, how do you get the figure of 41%?

If you print an 8 MP and 6 MP photo at the same resolution (the same number of pixels per inch), the 8 MP photo will have a surface area that is 8/6 = 1.33 times as large as the 6 MP photo. That means that it will be (square root of 2) x 1.33 = 1.15 times as tall and 1.15 times as high as the 6 MP photo. So, just 15% taller and 15% wider. That's not really spectacular.

[robertwgross]

Suppose you were going to shoot a wedding, and suppose you had several cameras on your shelf ready to go. One was 4 mp, one was 6 mp, and one was 8 mp. Which one would you take?

I would likely take the 8 mp, just because that is the way I am. But that is not the best answer, which is "it depends".

If you knew that the B&G wanted prints only up to 8x10 inches, then even the little 4 mp job would do it fine. If you knew that they wanted prints up to 13x19 or so, then the 6 mp job would do it fine. If you knew that they wanted big prints up to 16x20 or so, then the 8 mp job would be best. Note that very few people want prints that large.

---Bob Gross---

[tim]

I like to print at 20x30 inches, so the extra pixels are probably going to be at least mildly helpful for me. The 6MP Rebel did a pretty good job though, i'm very happy with the one i've gotten printed so far.

[gcogger]

Belmondo, how do you get the figure of 41%?

If you print an 8 MP and 6 MP photo at the same resolution (the same number of pixels per inch), the 8 MP photo will have a surface area that is 8/6 = 1.33 times as large as the 6 MP photo. That means that it will be (square root of 2) x 1.33 = 1.15 times as tall and 1.15 times as high as the 6 MP photo. So, just 15% taller and 15% wider. That's not really spectacular.

He wasn't talking about 8 vs 6. Note the quote

"A picture with twice the resolution is only a hair over 41% wider/taller."

[DocFrankenstein]

Belmondo, how do you get the figure of 41%?
we have 2 squares. Square with side x and square with side y.

One square has an area 2 times the other one.

Area of a square is length of the side squared.

Therefore => 2x^2 = y^2
Take square of both sides
x times root 2 equal to y

Works with rectangles too, if they have the same ratio of the sides. You on side as the other times 2/3. The two thirds cancel out and you're left with the same equation as above.

root 2 is 1.4142356....

So if one side of the picture is 100%, the other will be 141.42356%...

In other words, only 41% bigger linearly.

Cheers

[Phil V]

That depends on the film you're using. The grain of the film is not visible from Fuji Velvia 50 scanned on my Nikon V without grain desolver. This gives the equivalent of about 21mp.

But how about 8mp DSLR vs 800 iso print film. I don't want to turn this into a film vs digi debate but I thought that the presumption of film is best needed qualification. (best for what?):o

[robertwgross]

What you get out of a film result depends on the quality and resolution of your scanner.

My scanner gives me 100-150 MB files from each 35mm slide. That is a pretty big file, so I can print large with that.

---Bob Gross---

[mdr]

Are you in disguise? Einstein dressed up as Frankenstein :lol: .

[mdr]

Incorrect. It depends on the grain of your film provided your scanner is of a decent resolution.

[mdr]

You can't directly compare digital and film. It's not just mp and ISO.There's also costs, convenience, time and effort, but nobody ever seem to talk about dynamic range. ISO 800 film's dynamic range is far greater than any digital sensor. However, whether the naked eye can see this is in the final result is another mather. Film vs digital when it comes to ISO? Ho about film vs film battlefield of discussion when it comes to ISO. Is 400 ISO film uprated to EI 800 better than 800 ISO film?

[roanjohn]

Our friends at cnet just answered the question for you.

http://reviews.cnet.com/4520-6501_7-5138257-1.html?tag=cnetfd.sd

Ro1

[Chazs]

One other reason for 8mp (which I don't think has come up, and one on my list of reasons for getting a 20D someday) is the ability to crop a wee bit more. Sure, a zoom can help compose in the field, but even when I think a scene is composed perfectly when taking, the ambience may not be the same in print from, and a little cropping is necessary. Regardless of the size of print I want the 8mp will give some additional cropping freedom that the 6mp won't have (as well as some headroom in Photoshop). So why not go for the most MP possible? $$$$$$

[Belmondo]

Belmondo, how do you get the figure of 41%?

If you print an 8 MP and 6 MP photo at the same resolution (the same number of pixels per inch), the 8 MP photo will have a surface area that is 8/6 = 1.33 times as large as the 6 MP photo. That means that it will be (square root of 2) x 1.33 = 1.15 times as tall and 1.15 times as high as the 6 MP photo. So, just 15% taller and 15% wider. That's not really spectacular.

I see a couple people already straightened this out, so I won't add to it. Apparently you thought I was comparing 6mp to 8mp. Maybe I could've written in a less confusing manner. Sorry.

[mjordan]

It hasn't been mentioned, but the higher megapixel count will also give you better information in the shadows and highlights. It's still not equal to the lattitude of film, but if you take a lot of marginal light pictures, every little bit helps. If you only take studio pictures with controlled lighting, then it might not matter that much. Better resolving power in the shadows and highlights is one of the reasons I would go for the higher megapixle camera if I had the choice between the two. Not to mention the other features of a 20D over the 300D, like faster AF and buffer dumping. I shoot with a 10D now, so it's not quit enough to get me to upgrade to a 20D, but my wife shoots with my D30 and she's finding the limitations with it, so I'm thinking of giving her my 10D and getting the 20D... although the 1D MKII is my real choice if I could justify the cost.


Mike

[MDJAK]

I won't attempt to even place a toe in the mathematical debate going on. I don't pretend to even understand one little bit of it.

One thing I can say, from my own limited experience, coming from Nikon F100 to a Nikon D100 to a Canon 10d to now the 20d, I like the 20d by far the best.

Also, with my new EpsonStylus Pro4000, I just printed a photo in black and white and upped the printer's resolution (if that's the right word) from 720 dpi to 1440 dpi and the result, in 16x20 was spectacular.

[PacAce]

I see a couple people already straightened this out, so I won't add to it. Apparently you thought I was comparing 6mp to 8mp. Maybe I could've written in a less confusing manner. Sorry.


Don't know how you could have written it any clearer, short of using bold fonts. :confused:

That's a difficult concept for some people to get around. A picture with twice the resolution is only a hair over 41% wider/taller.

[hk29]

There was an article in one of the photo magazine that showed that the 16mb 1ds II outresolved film (not sure what film they were using).

Sorry I can't remember the mag. I can't wait until mainstream cameras are at this level...

[2112]

Hmmm? I am suprised no one mentioned this yet. MPs mean nothing really, the image sensor is the heart of the camera and what allows the light to come thru. The bigger the sensor, the more light you get, the better quality of pic, period. Compare images from a 6mp professional DSLR with a full size sensor to an 8mp "prosumer" camera with a smaller sensor and the 6mp image from the camera with the full size sensor will be better quality everytime.The resolution may be higher with an 8mp but the image quality on a camera with a full size sensor will always produce better sharpness, colors and an overall better image.

[mdr]

Just read an article in Black & White Photography comparing the 8mp Olympus 8080 with the 20D. Although the 8mp Olympus rivals the 20D for image quality on a bright day shooting at ISO 100, the 20D beats it hands down with shadow details and at higher ISO's. In fact the noise levels of the 8080 at ISO 400 are worse than those with the 20D at ISO 3200, due to the much smaller sensor in the Olympus.

[Cadenza]

So with an 8 mp sensor, it's like being able to take
a 6mp picture with a 1.84 magnification/crop factor;
since 1.6 x 1.15=1.84.

If you cropped a 20D's 8MP image to the central 6.1
megapixels in the proportional 2:3 form factor; you're
essentially end up with the same image as a 10D or a
DigiRebel with a 1.84 crop factor. Hence, your basic
70-200 zoom on a 20D becomes the equivalent of
129-368mm zoom on a 10D/300D.

Simmilarly, a 1DsMKII's 16MP provides 1.414 x on top
of the 1.3 crop factor of a 8MP 1D MKII, for a total of
1.83 multiplier effect for the central 8MP of its 16MP
sensor. Which makes one consider whether it is more
advantageous to buy a body with more megapixels,
or spend the money on longer telezooms.

Regards, Cadenza

[Andy_T]

Hmmm? I am suprised no one mentioned this yet. MPs mean nothing really, the image sensor is the heart of the camera and what allows the light to come thru. The bigger the sensor, the more light you get, the better quality of pic, period. Compare images from a 6mp professional DSLR with a full size sensor to an 8mp "prosumer" camera with a smaller sensor and the 6mp image from the camera with the full size sensor will be better quality everytime.The resolution may be higher with an 8mp but the image quality on a camera with a full size sensor will always produce better sharpness, colors and an overall better image.


2112,

I completely agree with you.
Most likely the reason why this has not been pointed out specifically is that this is the EOS forum where everybody is very much aware of the fact ;)

However, the question is valid, even here ... what will give better images, the original 1D (some years old by now) with its 4 MP 1.3 crop CCD sensor or the newer 20D with its 8 MP 1.6 crop CMOS sensor?

Basically, the 1D should let more light in (and its 4 MP CCD sensor surely is as sharp as a professional camera 3 years ago could be), but progress in sensor and processing technology allows for much better S/N ration in the newer camera enabling the 20D to take very good 1600 ISO or 3200 ISO images ... even at twice the resolution.

Best regards,
Andy

[tim]

Have to say the 20D at ISO 3200 is about the same as the 300D at ISO 800, give or take. Nice.

[gcogger]

You can't directly compare digital and film. It's not just mp and ISO.There's also costs, convenience, time and effort, but nobody ever seem to talk about dynamic range. ISO 800 film's dynamic range is far greater than any digital sensor. However, whether the naked eye can see this is in the final result is another mather.
I've seen plenty of evidence that a decent digital SLR has much greater dynamic range than any film. I haven't got any links here (I'm at work!), but I'll see if I can dig something out later...

[scottbergerphoto]

This response is along the lines of what 2112 had said. While the difference in resolution between the 10D and the 1DMII doesn't result in that much size difference in output, there is an enormous difference in the quality of the color and color transitions between the two cameras. I am not an engineer, so I don't know if it is due to the sensor size or # of mp's or what. The color from the 10D is great but the color from the 1DMII is like "butta". I noticed this right out of the box.
Scott

[Monito]

Hmmm? I am suprised no one mentioned this yet. MPs mean nothing really, the image sensor is the heart of the camera and what allows the light to come thru. The bigger the sensor, the more light you get, the better quality of pic, period. Compare images from a 6mp professional DSLR with a full size sensor to an 8mp "prosumer" camera with a smaller sensor and the 6mp image from the camera with the full size sensor will be better quality everytime.The resolution may be higher with an 8mp but the image quality on a camera with a full size sensor will always produce better sharpness, colors and an overall better image.

I don't believe there is any basis in physics for your statement.

[Monito]

Just read an article in Black & White Photography comparing the 8mp Olympus 8080 with the 20D. Although the 8mp Olympus rivals the 20D for image quality on a bright day shooting at ISO 100, the 20D beats it hands down with shadow details and at higher ISO's. In fact the noise levels of the 8080 at ISO 400 are worse than those with the 20D at ISO 3200, due to the much smaller sensor in the Olympus.

I don't think the sensor size is the issue at all. I think that the superior Canon sensor / processor technology is the trump card. The smaller 20D Canon sensor / processor is outperforming larger size sensors on all kinds of other manufacturer's cameras.

[Volatile]

I think 2112's point is 'amount of light per photosite' on the sensor, but Monito is also correct that materials and technology and processing are driving factors in sensor performance.

and that's all I have to say about that.

[Mark_Cohran]

Well, while the overall size may only be 15% linearly along the x & y axis, what I like about the additional 2 megapixels is the improved ability to crop and still produce a decent 8x10 or 11x14. That 15% may not seem like much for increased photo size, but it can (and been for me) critical when needing to crop.