How does 100% Zoom equate to Poster Size?

I often hear comments like, Do I have enough megapixels to print out a poster size print, or, How large of a print can I make with a M4/3 sensor, or, I'm never going to print a poster so I only need x-number of megapixels etc.

With that in mind, what does 100% Zoom actually tell you about your photo other than it looks sharp, fairly sharp, blurry, or somewhere in between when zoomed?

Does the quality of a 100% Zoom have anything to do with how large a print one can make or is it just a 100% crop of whatever number of megapixels are in the image?

Thank you for your input.

joslocum said:

... what does 100% Zoom actually tell you about your photo other than it looks sharp, fairly sharp, blurry, or somewhere in between when zoomed?

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That's mostly what it tells you - which is enough.

joslocum said:

Does the quality of a 100% Zoom have anything to do with how large a print one can make

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It might. If the 100% view on your monitor looks unsharp, you could expect a very large print of that image to look unsharp. It depends on the resolution of your monitor and how large you want to print.

joslocum said:

or is it just a 100% crop of whatever number of megapixels are in the image?

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100% view means you're seeing each square pixel of the image represented by one square pixel on your monitor. However, a pixel represented on your monitor is usually a lot larger than the same pixel that will be represented in a print. Thus, the print will almost always look sharper (and smaller) than what's seen on the monitor - except with very large prints.

If you're thinking about printing, two factors: dots per inch (essentially pixels) and viewing distance of the audience. Even at generic 300 dpi, it's not common for people to be viewing a print so close as to be able to see individual printer dots.

So it depends on what your specific situation is.

from past experience. printing a 7x5 foot print from my pentax K7 14 meg camera.

viewing an image at 100% on a 22inch 1920x1080 monitor looked exactlly the same in detail and image quality and that was looking close to the image not standing back.

If you are viewing an image at 100% zoom, it means you are viewing the image at its real resolution, meaning not upscaled (zoomed in) or downscaled (zoomed out). So if an image is 200 x 200 pixels, at 100% zoom it will show 200 x 200 pixels on your screen. If an image is 5000 x 5000 pixels, at 100% zoom it will show 5000 x 5000 pixels on your screen.

You see the image of this duck? You see it at its real resolution, meaning 100% zoom. The image is only 200 x 200 pixels which is waaaaaay too little to print on a poster. So this tells you that 100% zoom is not related to poster size in any way.

As being well explained by members before me, the resolution would determine how large an image could print (based on XXX ppi) and sharpness or fine detail would depend on the viewing distance. I think you could find sample of road side posters that the image might indeed be made up by an image of itself just while looking at it at a far enough distance, we human eye would think it is just dots making up the picture!

To view an image at 100%, to me is for the sole purpose to examine the original sharpness of the output down to pixel scale. I wish the following 2 SOOC JPGs might explain myself:

A 16Mp image on full screen view mode of my 1080 monitor (around 17% view):



It is not very sharp on full screen view. But when examine at 100%, it was very bad, not a keeper to me:





Another 16Mp image displaying on 1080 monitor at 17% view, apparently it is looking only marginally sharper than the above failure sample:





When examine it at 100%, I am happy with the focusing condition:





Accurate focusing is one of the few other basic ruler for me to determine the technical aspect of output. 100% view is the best tool for it.

--
Albert
** Please forgive my typo error.
** Please feel free to download my image and edit it as you like **

joslocum said:

I often hear comments like, Do I have enough megapixels to print out a poster size print, or, How large of a print can I make with a M4/3 sensor, or, I'm never going to print a poster so I only need x-number of megapixels etc.

With that in mind, what does 100% Zoom actually tell you about your photo other than it looks sharp, fairly sharp, blurry, or somewhere in between when zoomed?

Click to expand...

The 100% view tells you nothing much except for detail sharpness as you say.

joslocum said:

Does the quality of a 100% Zoom have anything to do with how large a print one can make or is it just a 100% crop of whatever number of megapixels are in the image?

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It is best to think of potential print quality in terms of the number of original camera pixels per inch of print.

For super sharp that will allow people to get really close and still see detail then about 300 camera pixels (or more) per inch will achieve that.

In real life from personal experience battling low MP cameras then a really good print that will handle some close scrutiny and get away with it can happen as low as 200 camera pixels per inch of print. Below that at your peril and I took it as low as 185 camera pixels per inch on occasion and still looked OK but I'd rather be at 200 or above.

If a very large print is viewed at the appropriate distance of the diagonal measurement then about 4MP to 8MP will be really good, but up close will look soft.

So it all depends on how it will be viewed, in a gallery behind a rope then lower res is fine, if someone can get their nose up against it (visual pixel peeping) then it had better be 200 pixels per inch and up.

Ignore interpolation to get the pixel count up as that does not add missing detail. Some AI methods may help but adding false detail is not wise or honest.

Divide the number of X and Y pixels on your image with those on your monitor and multiply the results with the dimensions of your monitor and you will know which size print you are looking at a crop of. For any other zoom ratio divide/multiply by appropriate number. Handy way to judge how detailed your print will look from different distances.

joslocum said:

I often hear comments like, Do I have enough megapixels to print out a poster size print, or, How large of a print can I make with a M4/3 sensor, or, I'm never going to print a poster so I only need x-number of megapixels etc.

Click to expand...

My rule of thumb is nothing less than 300 dpi (120 dpc) for professional printing. (magazines/posters etc.) and I will stick to that at home too (inkjet) although occasionally going down to 200 dpi if I have to. The worst situation is a friend or relative asking for a print from a grubby little mobile telephone file.

I hardly ever use 100% zoom except for analysing potential lens/focus faults.

Likely viewing distance of the final print is hugely important. Two of my most financially successful prints were made into 1m x 1m posters used at a travel exhibition. The images had come from a humble D70 (6mp). This was OK though as the public could not come closer than about 5m.

I've read that a human with really good eyes, in good light can resolve 0.04mm at a viewing distance of 15cm. That factoid could perhaps be used to address the question.

I keep most of my own personal images at enough resolution for no more than A4 size 300 dpi prints.

A74Me said:

from past experience. printing a 7x5 foot print from my pentax K7 14 meg camera.

viewing an image at 100% on a 22inch 1920x1080 monitor looked exactlly the same in detail and image quality and that was looking close to the image not standing back.

Click to expand...

Good stuff! Thanks for posting.