Resolution Question

[carl365]

In creating a new image, wondering if there's some rule of thumb on what to set the resolution to. It goes from 1-2000 but Corel help doesn't explain how you select the right number.

Thanks!

[LeviFiction]

Resolution is strictly for printing. If you intend to print your image then some simple math will tell you what resolution you should use. But it's not important right away as you can use the Resize command to change the resolution without actually resizing your image.

And how you set the resolution depends on how detailed you want the print. There are lots of tutorials and guidelines online for what the best resolution is for what job. Sadly I don't think I could explain it well. Most people use a standard default of 200 or 300. And usually these are meant to be printed out and viewed at arms length. So 4x6s and 8x10 photographs.

But if you're only going to be showing it digitally, like on the web or through a thumbdrive or something like that. then the resolution is meaningless and a standard 72 or 96 will suffice.

[carl365]

Ah that clears it up. By the way I've been looking at and following your Youtube tutorial videos, learning a lot.

Thanks!

[JoeB]

As LeviFiction said, resolution is also better known as "print resolution" and is measured as "pixels per inch" or ppi. It determines how many of the pixels in your image will be printed per each inch of the printed image. The human eye, when viewing an image at about arms length, is generally considered capable of seeing an image that contains 200 ppi as a smooth, non-grainy image and the detail provided by those 200 ppi is about all the detail the human eye is generally capable of noticing. However, it pays to err on the side of caution and use 300dpi as your resolution for images that will be viewed at arms length, which means photos between 4"x6" or even somewhat larger.

If there are too few pixels printed for each inch of printed photo (e.g., 100ppi) the image will appear grainy because the smaller number of pixels per inch have to be spread out throughut that printed inch of photo meaning more space between the pixels. However, the further away that an image is meant to be viewd the fewer pixels per inch that are needed. That's because the human eye can't see as much detail the further away an image is and the eye/brain interaction will fill in the extra spaces caused by the lower resolution (it interpolates information that isn't actually present in the image). Older painted highway billboards that were meant to be viewed at a very long distance could often get away with containing only 4 pixels per inch because of the distance they were meant to be viewed and the resolving power of the human eye and brain in concert.

As an example of how ppi works, if you have an image that is already 1200 pixels wide and 800 pixels high and set the resolution at 200ppi it will print an image 6"x4" (a standard photo size) that will look just fine to somebody viewing it at arms length. You can calculate that by dividing the pixel dimensions by 200 (the pixels that will be printed for each inch of printed photo). But if you want to print it at 400 pixels per inch, by dividing the dimensions by 400ppi you will see that the image will print at 3"x2".

But let's assume your image is 2400 pixels wide and 1600 pixels high (twice the pixel size of the above example) and you want to print it as a 6"x4" image. Then you have two choices. You can resize it to 1200x800 at 200ppi OR you can decide you don't want to throw away those extra pixels by resizing and resampling and instead leave the pixel size as is and set the resolution to 400ppi. As the math shows, you'll still get a printed image of 6x4 inches, just with a higher pixel density per inch of printed size.

In the days when storage was expensive many people would resize the image to the minimum pixel size needed to achieve the required print size at the required resolution. But with storage large and cheap nowadays it is often prefereable to simply leave the large file size caused by modern cameras that take multiples of megapixel images and just change the resolution in the resize dialogue to achieve the print size needed. That leaves your large megapixel original available in case you want to use it to print a much larger image such as 16"x24" and have plenty of pixels available to still set a decent resolution of 200ppi. 200ppi and even a bit less works well for such a large image because it is likely to be framed and viewed at a distance somewhat further than arms length.

[carl365]

Thanks a lot JoeB, I save all this great info in my PSP folder.

[brucet]

Go to you Preferences/Units. Set Default resolution to 300 Pixels inch.

Save and forget.

The only time you then need to consider 'resolution' is if and when you want to 'share' your photo in someway. You can then use Image/resize to suit the end use.
FWIW I never change it unless sending an email attachment or posting online.

regards

[hartpaul]

Pixels for display, sharing and any non printing use.
Dpi + the necessary amount of pixels for printing at what size is needed.


What gets me is when a printer for a newspaper asks for an image and says 1 Mb image.
They don't seem to realise that depending on the compression and file type a number of different pixel size images can have a 1 Mb disk space size.
I finish up asking them how many inches they want to print the photo approx and then multiply that by 200 to get the pixels size and then save the image with only 4-10 PSP compression depending on the quality of the paper.

[carl365]

Thanks for even more help guys, hartpaul, brucet. All put into my PSP folder.

[brucet]

I had a multi national printing company license one of my photos for a print run of over 4 million copies. (Calendars). When I asked what 'size' file they wanted they simply told me to send them the largest file I could. So off went a 450meg tiff. The resultant calender was a very poor reproduction that could have been done with a 72dpi file. My point being that over a period of time you can find a zillion different versions of 'what is right'.

Always use the biggest possible and let the end user worry about the conversions.

regards

[hartpaul]

Except when they say email it and no larger than 1 MB.