Understanding DPI?

Granty_

Granty_

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760
Name
James
Edit My Images
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Hi all,

I fully understand that pixels are for monitor viewing and DPI is for printing.

However I've always exported at lightrooms default 240 dpi, this leaves the pixel count of my images as they should be for my camera.

However, now I'm doing submissions to magazines they ask for 300dpi. I am having to upscale all my pictures in photoshop to 300dpi and I fear reducing the quality of the image especially when the pixel count goes up with it.

Should I be exporting at 300 dpi initially? What does everyone else do?

Thanks,

James
 
Hi,
Not too sure about your question, I asked a similar one the other day. Someone sent me a good link, I will try and find it.
I must say not only do your images look very good but the website lay out is very clear and clean, it looks good. Who is it through?
 
Thanks Amac. Its a bit hard to get my head around, I export at 240dpi as standard and happy with the quality. This is suffice for web viewing.

Why the magazine wishes for 300dpi when they dont print up to a big enough size to justify it I don't know.

Thanks for the comments on the site, I designed it and my mate coded it (with a bit of nudging from others as well to get it fully tweeked) and host it myself. Its nice to have something bespoke, but its also a pain when its not as automated as you may like to add photos.
 
Your camera doesn't export images at any sort of DPI, it just provides images that measure X pixels by Y pixels. The software that you import your photos into on your PC will impose a default DPI, but even then, this figure will be meaningless, as it won't change the size of your image file, which will still measure X by Y as supplied by the camera.

The only time DPI becomes relevant is when you send your file to print, and you want your print at a specific size and at a specific resolution. The magazine says it wants your images at 300dpi, but without knowing how big the printed image is going to be, how are you supposed to work out how large the image is supposed to be? If they want to print at 4x3, then you need to supply an image that measures 1200x900 pixels to meet their 300dpi requirement. But what if they want to print at 7x5? If that's their intention, you need to supply an image that measures 2100x1500 pixels.

The easiest thing for you to do is find out what their minimum size requirement is expressed in pixels, rather than a DPI requirement which can't be interpreted without knowing how big the print is going to be.
 
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Notwithstanding Scarecrow's well reasoned post above...

X-resolution and Y-resolution (specified in dpi) are legitimate tags in the EXIF standard. It sets a nominal size for the image, such as when viewed at 'Actual size' in a number of image viewing applications; Photoshop has a View > Print Size command, for example.

It may simply be that the magazine sets a particular standard for the images it uses for a number of reasons.

- to set a minimum standard for images at their intended published size (especially if you're selling your images rights-managed you may well/should have an idea what that is to be)

- more specifically, to exclude low resolution (pixel-wise) images grabbed from the web

- it's a hang-over from the days when images were drum-scanned to order to a specific size for publication

- I also seem to recall that back in the 90s it was more efficient for PostScript RIP software (which converts the page layout into the final plates for press) if all the images on a page were at the same nominal resolution, but I may be imagining this.

Additionally, If they're using some automated pre-screening software because of the volume of submissions they have to deal with, it may be rejected if the dpi resolution does not meet the standard. They may also have a fussy legal department that prevents them from further modifying the image after they've received it.

If you're exporting from Lightroom to JPEG or TIFF files with EXIF data intact and you're providing the full-size (pixel-wise) image, then you can almost certainly specify 300dpi in your export dialog and have done with it.

If you have the exact required published size specified, you should set the export dimensions and the dpi accordingly.

Resizing after export from LR sounds like a bad idea on all levels.

P.S. I'll try to avoid getting into a DPI/PPI/SPI/LPI discussion :)
 
there are two ways of changing the DPI

1/ changing the DPI and keeping the pixel count the same - this changes the size of the printed image.

2/ changing the DPI which changes the pixel count to keep the image the same size.


When you convert from RAW there should be link to let you choose what DPI the RAW is converted.

onedt.jpg


then when you resize if you uncheck the resample image, you can adjust the DPI without changing the pixel count

twowx.jpg
 
Granty_ said:
Thank you for all your responses - I have changed the DPI and unticked the resample image to ensure pixel count hasn't changed, this hasn't seemed to have any discernible effect on the quality of the image.
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Yep. It won't.
 
In terms of magazines using images and knowing how to supply them, the easy answer is to supply at original size (i.e. 4200 x 3400 or whatever your camera captures images at).

Repro departments at magazines vary in how they approach image adjustment and resizing - they all have their own working styles - but generally, at my place, I supply the original JPEG or raw file and it's resized according to whether it's being used as a panel (generally less than 10cm x 10cm), single page or DPS - DPS use usually means a bit of interpolation is required. The downsizing is generally to save space, although I keep everything I shoot at original size just in case that shot is required in future.

Our Canon's output at 150ppi whereas my D2X outputs at 300ppi - regardless, they're all a specific pixel dimension depending how many megapixels the sensor is.
 
The problem with a lot of designers is their software,(usually InDesign, or Quark) is set by default to 300dpi. The problem is that they just import the image and if it doesn't scale to the template it gets rejected as being too small.

The answer is simply to ask what size they need it and size it up to that size a 300dpi. It saves so much hassle i the long run
 
Granty_ said:
I know not quite with the same topic - but if a magazine asks for RGB do you think they mean "Adobe RGB" and "sRGB" or just Adobe RGB?
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Doesn't really matter - they'll convert to CMYK for print reasons.

BTW, I shoot sRGB for magazine work because it seems to make the repro guys happy. Something about Gamuts and colour spaces.... When you shoot for mags the one person who you have to put 100 per cent trust in the repro guy; they can make or break an image.....

My advice us supply direct from camera and you'll have no proves with supplying the wrong image size or dpi. I only speak from the 10 years I've worked at my place but they process to the proof, meaning what you, the photographer, thinks is the correct processing isn't always correct for the printing process. I've processed some stuff that I think looks the nuts that turns out looking pants in print
 
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Chappers said:
The problem with a lot of designers is their software,(usually InDesign, or Quark) is set by default to 300dpi. The problem is that they just import the image and if it doesn't scale to the template it gets rejected as being too small.

The answer is simply to ask what size they need it and size it up to that size a 300dpi. It saves so much hassle i the long run
Click to expand...

It is very rare for a magaine to know what size of image they require before the pages are actually designed. Which only happens a few days before going to press. Almost all magazines are printed at 300dpi.

Until it is in the designer's hands, it is unlikely anyone will know for sure what size it will be used, and even then it's quite likely to be cropped.

Submit the file as it came out of the camera. They will scale it down, or up, as necessary.
 
Agreed with Hoppy - I can pretty much tell if an image I shoot for an opening dps ( double-page spread) will get used as intended but that's only because I know how my editors think and I know what works in te mags I work on. Aside from that, the designer will be given the choice of images to work with and will use them as they see fit. On instructional mags the only time I know an image won't go bigger than 10x10cm is if it's been shot as part of a sequence, such as a knot-tying sequence.
 
specialman said:
Agreed with Hoppy - I can pretty much tell if an image I shoot for an opening dps ( double-page spread) will get used as intended but that's only because I know how my editors think and I know what works in te mags I work on. Aside from that, the designer will be given the choice of images to work with and will use them as they see fit. On instructional mags the only time I know an image won't go bigger than 10x10cm is if it's been shot as part of a sequence, such as a knot-tying sequence.
Click to expand...

Yeah, that's a good example of a knot-tying sequence. It's quite possible that the designer might pick out one good image and blow it right across a spread, ie A3 approx, and the actual sequence shots plus the text and diagrams etc will be overlaid on the main image, in small panels etc. They might be no bigger than a couple of inches across, or less, or cropped, or both. Other images might be dropped on to the cover at a different size, or on the Contents page. Then the images will be filed for possible future use, at any size.

There's no way of knowing which images will be used at what size, until the designer has finished. Anybody that tells you otherwise does not work in the production department - probably sales or marketing :lol:
 
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