How many pixels do you need.

As a film SLR photographer in a previous incarnation, I used to use Velvia (remember that guys?).

Forgetting about colour reproduction, dynamic range and other issues for a moment, I would be interested to know what people think is the number of megapixels that would/will match Velvia for resolution.

I'd also be interested to know what evidence led you to arrive at that number.

I have my own opinion about this, but I'd love to hear what you think.

You can only judge this based on direct comparison of the results. In the real world 6.3 megapixels of 10D DSLR is almost as good as 35mm velvia. The 11+ megapixels of the 1Ds is definitiely superior. I still shoot 6*9 medium format on Velvia, which will outperform even a P25 MF back - but only just, and if I could afford a P25 I'd be willing to throw out my Velvia altogether.

Check out Reichman's review of the 1Ds on luminous landscape - he compares the camera to 35mm film, and it's not much of a contest.

Hi Andrew,

I think that it also depends on whether you are printing direct from slide, scanning on a drum-scanner, or scanning on an good desktop scanner. Also digital camera images can be interpolated much more reliably than scans of film images, because the data starts on a regular grid.

On a recent advertising projected (for large banner posters) I got this email back from the client's art people, who were very impressed by my image quality:

"Has he scanned those 2 images in from 35mm slides? Or large format trannies? Can you ask him how he has scanned them, and what scanner he has?

They are very very good quality if they are from 35mm slides, and the size is great for our needs..."

The images were in fact from a D100!

Alex

Hi Andrew,

Because there are so many variables that impact on image quality and a digital sensor array does not respond to light the same way that film does, we are sort of comparing apples and oranges when we talk about film-digital comparisons. The following procedure, however, will give you a fairly good way for you to determine how many megapixels you may need to fullfil your needs.

If we accept that the average human eye can resolve ?180 pixels per inch at a 12" viewing distance, and if we also accept that when we increase the input resolution of the output to 200 pixels per inch, the output will look continuous tone, we have our constant to start our calculations.

First, we determine what is the largest print we want make to be viewed at 12" away and to appear to be "film" quality"(continuous tone). Let's use 11x14 for an example. Multiply 11x200, 14x200, multiply the products together to arrive at the number of pixels we need.

(11x200)(14x200)=2200x2800=6,160,000

Therefore, we need a 6 megapixel camera to output an 11x14 print to be viewed at 12" away and appear continous tone.

Keep in mind that larger prints can also be made and appear just as good as long as the viewing distance increases appropriately as the print size increases.

I hope this helped.

Arthur

Hi Andrew,

Interesting question! I have been making a lot of prints over the last month, to give away as gifts, and decorate my new house and office. Over the past two years, I've used the Fuji S2pro, D100, and Kodak ProSLRn extensively. I printed sizes from 8x10 to 32x32 using the digital files and Pictopia.

Like Arthur said, I have been pleased with the 6 megapixel images out of the D100 us to 11x14. By quite pleased, I mean I would consider them VERY difficult to distinguish from film. Going larger, to 16x20, I was not as happy, but the 12 Megapixel images rendered from the 6 megapixel Fuji SuperCCD were still in the same glass.

At 16x20 the Kodak images were "better than film" in terms of low noise/grain and overall punch and look. At 32x32 (cropped to square) from the Kodak, the images were still as good as film. I was totally shocked and blown away. The Kodak is SO sharp because of the lack of anti-aliasing filter. I don't think I would have been happy with the 6 megapixel images as I would have only had 2000 pixels to work with and the blur from the AA filter instead of 3000 and no AA filter.

I guess that's a bit overtechnical, but the bottom line for me at least is 6 megapixel up to 11x14 = great. 14 megapixel up to 20x30 = great.

Cheers

James

Hi!

For a 2:3 chip 6Mpix is ok, for a 3:4 chip 5Mpix is sufficient to get an appealing image quality at a normal viewing distance.

When blowing up film images you get lots of grain but no detail. We just got used to this. Blowing up digital needs a good algorithm to avoid scaling artefacts.

I saw a test where they compared digital 6x6 sensors versus slide film on a Hasselblad. The slides were scanned on a professional drum scanner.

Digital (Kodak, Phase One, Sinar) were nearly equal in performance but outperformed the slides in all cases. Dynamic range 12 stops, better colour reproduction, more detail.

When scanning a 35mm slide with more than 6Mpix you just get fine details of the grain (and waste valuable disk space).

Helge ;-)=)

As a recent convert from the D100 to film (velvia/provia), I feel that the detail of my D100 matched or exceeded the detail I get from velvia scans on my coolscan 9000. I think that the dynamic range of velvia is far superior to the D100 or any other digital files I've seen.

I believe that the measured dynamic range of digital sensors is misleading because it stretches into the shadows while clipping the highlights. I'd prefer clipping the shadows to black, but maintaining detail/contrast in the highlights like velvia does. The measured DR may be similar, but the pictures that they create are far different.

I happen to like black shadows, but I hate white sunbursts. I've found that images that would've had very distracting backgrounds with my D100 (or required major photoshop adjustment) often have dark or black contrasty backgrounds with velvia.

I haven't given up on digital yet, but I expect more from the next generation!

I've got a 24x36 picture hanging on my wall that was done from a 6 megapixel D100 image. It's sharper and looks better than any of the 20x30s hanging nearby that were printed from 35mm slides.

I've also had several two page spreads in magazines from D100 images (shot as jpgs, not RAW). See 12 December 2004 Geo, pp 24-25. Also, the July 2004 cover of Sport Diver was cropped from a horizontal D100 image.

My opinion: 6 megapixels is more than adequate for professional work.

Film and digital aren't the same. It's not fair to either medium to try to quantify a comparison.

How many Porche Carreras does it take to make one pickup truck?

Many digital images, because of sharpening algorithms, appear "more real than reality". Film can bring out subtle tone (zone) differences you wouldn't see with your eye. It's a different "look" to each media.

So I guess I'm pointing out that when it comes to color depth and exposure latitude, the answer to your question would be: "None. There's no digital sensor easily available to match film". However, in terms of resolution and contrast, 6 megapixels (less, even) are easily a match and can surpass film.

Pick the tool that fits the image you want to make.

All the best, James

Oops. Sorry, Andrew, I should have re-read your question!

To the point:

My D100 slightly beats out Ektachrome E100G in pure sharpness.

I used Koren charts, and:

D100

F3

55mm Micro f2.8

ImageJ

Bessler 23CXL

EL-Nikkor 135mm f 5.6

All the best, James

I am not in the professional league, but, i think scanning a 35 mm and comparing it to a digital picture is not valid. To my understanding, velvia film has actually something like 40MB woth of data on, but scanners - is there as 35 mm drum scanner which is that fine ?

If u were to take 20% area of i.e. a small fish, on velivia, and enlarge it photographically to i.e. 14-by-x inches, and did the same digitally on a 6 m.pix, would the results come out the same.

Any way, acedemic really........ u guys will be glad to know that Caveman is compenplating moving to digital. Dx2 @ $10,000 ( forget it), so it looks like the S3 and the D70 are what I will be aiming for. (advice ?)

Here is a quote froma guy on DP review. It does not look like he is a firm believer in the 12 MP theory....... ( i m interesting in this as i am looking at D70& the S3)

Quote:-

I don't buy into the 12 megapixel (interpolated) quality. If it comes out 6 megapixel, it's 6 megapixel - why should I have to post process the images to get the higher res?

The "wider dynamic range" was unnoticeble on screen. I guess in order to really see the difference I'll have to compare large prints of same image from my own Nikon D1x or my Canon 20D, but I'm not going to because I have an idea how the results will turn out.

snip... i think scanning a 35 mm and comparing it to a digital picture is not valid...snip

Just to clarify (sorry I didn't); the Ektachrome results were derived optically.

All the best, James

My opinion as sport photographer for some internet magazines and newspapers.. I need max 2-3 Mpixel for my work but let we say that 4-6Mpixels are probably quantity that will make 99.9% of people happy and they don't need more then that.

Pumping up the pixels in cameras are only solution for better marketing because many normal people think that Mpixels make camera good. For me better thing is that then make some other things not only pumping pixels, like (better chip quality, lower noise at high ISO, faster shutter speed, bigger buffer, faster flash sync, dustcleaning in camera (like Oly E-1), live preview at LCD and many other things)