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Inches to pixel count
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Jan 14, 2022 20:36:25   #
trapper1 Loc: Southside Virginia
 
The Virginia Dept of Wildlife Resources publishes an annual issue depicting flora and fauna native to the Commonwealth of Virginia. They accept pictures for inclusion and designate the size of the images submitted for the article as a minimum of 4" X 6". I am familiar with manipulating the size of images using pixel count but have no idea of how to convert inches to pixels. All of the images in my computer are of course identified in part by pixel size, not inches. Is there a formula for converting images from pixels to inches and vice-versa?

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Jan 14, 2022 20:43:02   #
CHG_CANON Loc: the Windy City
 
That's a poorly worded requirement for digital images, but to hit the minimum, assure your image is cropped in a 2x3 aspect ratio and at least 1200x1800 pixels. If you think you can get a full-screen presentation of your images, online, maintain the 2x3 aspect and use 2048px as the long-side pixel resolution. Or even, 2000x3000px.

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Jan 14, 2022 23:50:57   #
trapper1 Loc: Southside Virginia
 
As always, your advice is gretly appreciated. The images in my computer are all uncropped JPG. I wll use the 1200x1800 pixels you suggest and see how that goes. Again, thank you for the information.

trapper1

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Jan 15, 2022 00:08:24   #
flip1948 Loc: Hamden, CT
 
trapper1 wrote:
As always, your advice is gretly appreciated. The images in my computer are all uncropped JPG. I wll use the 1200x1800 pixels you suggest and see how that goes. Again, thank you for the information.

trapper1

So you are going with the minimum size of 4"x6" at 300 dpi. Did they give a maximum size?

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Jan 15, 2022 08:47:21   #
tcthome Loc: Keansburg , NJ
 
What software are you using. I use Lightroom. I just pick inches & put the desired size in, in the export dialog box/window. easy peasy, along with jpeg which chooses srgb for color space.

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Jan 15, 2022 09:18:38   #
BebuLamar
 
trapper1 wrote:
The Virginia Dept of Wildlife Resources publishes an annual issue depicting flora and fauna native to the Commonwealth of Virginia. They accept pictures for inclusion and designate the size of the images submitted for the article as a minimum of 4" X 6". I am familiar with manipulating the size of images using pixel count but have no idea of how to convert inches to pixels. All of the images in my computer are of course identified in part by pixel size, not inches. Is there a formula for converting images from pixels to inches and vice-versa?
The Virginia Dept of Wildlife Resources publishes ... (show quote)


They only specified the minimum size then simply submit whatever you have. That is you can submit a full 60MP image and they wouldn't complain. I would say they would complain if you submit something less than 1800x1200 but I think all your images are larger than that.

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Jan 15, 2022 09:58:33   #
trapper1 Loc: Southside Virginia
 
flip1948 wrote:
So you are going with the minimum size of 4"x6" at 300 dpi. Did they give a maximum size?


No maximum size, just the minimum.

trapper1

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Jan 15, 2022 10:08:11   #
trapper1 Loc: Southside Virginia
 
[quote=tcthome]What software are you using. I use Lightroom. I jus.........

I just alter the size of the image as it appears in "Pictures" in my computer, using the tools included in that program.

trapper1

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Jan 15, 2022 14:18:55   #
SuperflyTNT Loc: Manassas VA
 
tcthome wrote:
What software are you using. I use Lightroom. I just pick inches & put the desired size in, in the export dialog box/window. easy peasy, along with jpeg which chooses srgb for color space.


Not at all what they mean. They’re looking for images that are high enough resolution to be able to print at 4”x6” while maintaining IQ

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Jan 15, 2022 14:26:25   #
tgreenhaw
 
A basic rule of thumb for printing is 300 pixels per inch (ppi or dpi), so 4X300=1200 pixels & 6*300=1800 will yield acceptable results on a 4"X6" print.

If its going to be printed with offset lithography with halftone dots, you will want at least twice the halftone line screen. Newspapers will typically use 85 line per inch, so a minimum 170 ppi is warranted with more for images with line art components. Magazines and glossy ads generally use 150 or 175 lpi halftone screens, so for that target print media a minimum or 300 or 350 ppi is needed.

That said, you can get away with pretty good quality at 240 pixels per inch in a pinch.

If the image has high contrast line art, type or very fine detail, the higher the better with 800 pixels per inch a reasonably high resolution with more usually being overkill.

There are programs like Topaz Gigapixel AI that often do an amazing job up scaling images if you image resolution is insufficient. This is especially important when printing very large prints especially on metal. Scaling images up in most other programs will generally just make them blurry with little to no gain in quality.

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Jan 15, 2022 14:33:15   #
profbowman Loc: Harrisonburg, VA, USA
 
I would make certain that my photos are passed on with the 300 dpi set when you go with at least 1200 X 1800 pixels which would then be equivalent to a 4" X 6" print. Your camera may attach this data in the EXIF info to the photo or they may have a default dpi of 180 or 350 or something else.

I am sure all photo editors will let you change the dpi, but here are the directions for IrfanView, which I know quite well. Therre are two ways to do this.

1. With the photo open in IrfanView, go to Image/Information. Then change or check the dpi. If you change it, it will not be in effect unless you also press the "Change" button.

2. With the photo open in IrfanView, go to Image/Resize (Resample). In the new sub-window, one can change the size in pixels of the photo or not. The dpi is shown and can be changed new the bottom left of that window.

--Richard

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Jan 15, 2022 20:51:48   #
Greg from Romeoville illinois Loc: Romeoville illinois
 
trapper1 wrote:
The Virginia Dept of Wildlife Resources publishes an annual issue depicting flora and fauna native to the Commonwealth of Virginia. They accept pictures for inclusion and designate the size of the images submitted for the article as a minimum of 4" X 6". I am familiar with manipulating the size of images using pixel count but have no idea of how to convert inches to pixels. All of the images in my computer are of course identified in part by pixel size, not inches. Is there a formula for converting images from pixels to inches and vice-versa?
The Virginia Dept of Wildlife Resources publishes ... (show quote)


I am confused by all the answers to this question. I assumed that the amount of pixels in a picture varies based on the amount of PPI and that changes based on how big you blow a picture up. In other words if you had a PPI of 96, it would translate to a 384 x 586 pixels but if you had a 60 PPI it would translate to a 240 x 360 pixels.

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Jan 15, 2022 21:02:11   #
CHG_CANON Loc: the Windy City
 
Greg from Romeoville illinois wrote:
I am confused by all the answers to this question. I assumed that the amount of pixels in a picture varies based on the amount of PPI and that changes based on how big you blow a picture up. In other words if you had a PPI of 96, it would translate to a 384 x 586 pixels but if you had a 60 PPI it would translate to a 240 x 360 pixels.


This post provides a detailed discussion along with several graphics / examples that demonstrate the issues:

Recommended resizing parameters for digital images

Pixels Per Inch (ppi) is a calculated value. You need to know the desired print size in inches and the target pixel resolution ratio. The 'gold standard' for physical printing is 300 ppi, while in reality, a value as low as 150 ppi is acceptable, especially for larger overally print sizes.

The OP's question and the posted requirements don't speak to a need / plan for physical printing; therefore, expressing the requirement for inches is hard to understand clearly what is being requested.

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Jan 15, 2022 21:10:52   #
frankraney Loc: Clovis, Ca. For the last 50 years.
 
trapper1 wrote:
The Virginia Dept of Wildlife Resources publishes an annual issue depicting flora and fauna native to the Commonwealth of Virginia. They accept pictures for inclusion and designate the size of the images submitted for the article as a minimum of 4" X 6". I am familiar with manipulating the size of images using pixel count but have no idea of how to convert inches to pixels. All of the images in my computer are of course identified in part by pixel size, not inches. Is there a formula for converting images from pixels to inches and vice-versa?
The Virginia Dept of Wildlife Resources publishes ... (show quote)


They will print at what ever pixels they print. But if they want 4x6, multiply that by 300, so 1200x1800 pixels will suffice.

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Jan 15, 2022 22:03:30   #
SuperflyTNT Loc: Manassas VA
 
Greg from Romeoville illinois wrote:
I am confused by all the answers to this question. I assumed that the amount of pixels in a picture varies based on the amount of PPI and that changes based on how big you blow a picture up. In other words if you had a PPI of 96, it would translate to a 384 x 586 pixels but if you had a 60 PPI it would translate to a 240 x 360 pixels.


A digital image has no physical size, it has a resolution. A Nikon D500 has a 20.9 megapixel sensor. An uncropped image from that camera is 3840x2160 pixels. If you have a standard wide monitor that’s 1920 pixels wide that image, displayed at full screen, is actually compressed. At full 1:1 resolution only a little more than 1/4th of the image would fit. It’s generally accepted that for an 8x10 print or smaller you want 300 pixels per inch. So for a landscape print of 8x10 you’d want an image that was at least 3000 pixels by 2400 pixels, 4x6 you’d need 1800x1200. So know you might think, “how can I print a 16x20 from my D500? I need an image that’s 6000x4800”. Well that’s where viewing distance comes in. You’re not gonna be viewing a 16x20 at the same distance that you view an 8x10 or smaller. The farther away the viewing distance is the less DPI you need. Billboards are usually printed at only 15 DPI.

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