# How do I determine which DPI to use when export in LR?



## duydaniel (Jun 27, 2013)

When export raw to jpg, you have to put in a DPI like 200, 300... etc
I assume it means dot per inch, but I don't really understand how that works?
Can someone teach me?

Thanks in advance


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## Rofflesaurrr (Jun 27, 2013)

DPI is irrelevant if you are exporting images for viewing on a computer. If you are printing, then you'll usually want to set it to at least 300 DPI for most commercial printers.


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## duydaniel (Jun 27, 2013)

Say if I have a 23 megapixels (Canon 5D3).
What are the differences in print result if I export say 300 dpi vs 400 dpi?

Would I be able to print larger or something?


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## Drizzt321 (Jun 27, 2013)

duydaniel said:


> Say if I have a 23 megapixels (Canon 5D3).
> What are the differences in print result if I export say 300 dpi vs 400 dpi?
> 
> Would I be able to print larger or something?



Most printers won't be able to do above 250-300 dpi (I believe, I'm not a professional printer). That dpi setting is nothing more than a bit of data put into the EXIF metadata. What you need to look at is size of the print you are making, then the dpi setting you want, then figuring our your long & short edge minimum pixel output resolution.

Also, for larger prints, you actually don't always need a higher resolution file. If it's going to be view 15 or 20 feet away, you can get away with quite a low dpi. If you want someone to be able to walk right up to it and view it from a foot or so away, you will need a very high resolution file. I've heard that most billboards are actually printed at something like 100-150 dpi.

Also, if you send a higher resolution image than is needed (or the printer is capable of handling) it will automatically get resized to fit the requirements of the printer & output size. So if you export it to match the needs yourself, you'll be able to see exactly* what will be printed.


* You also really need to be in a fully color managed workflow, profiled monitor, printer ICC profile and do a proof and/or test print to make sure the colors are as desired.


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## Malte_P (Jun 27, 2013)

duydaniel said:


> Say if I have a 23 megapixels (Canon 5D3).
> What are the differences in print result if I export say 300 dpi vs 400 dpi?
> 
> Would I be able to print larger or something?



as said DPI is irrelevant for viewing on a PC.

it only tells the printer how BIG it shoudl print, it will change nothining on the pixels.

it´s just the info "hey printer print these 2000x4000 pixel at 20x40cm".
and if you set it to a higher dpi you may say "hey printer print these 2000x4000 pixel at 10x20cm"


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## STEMI_RN (Jun 27, 2013)

It just comes down to the print resolution. 300 DPI is the standard, but you can find printers that print even higher than that. The reason this becomes important is that you can't print (and still look good) at less than 300 dpi. So you have to look at the max resolution of the image (for a 5D3 that's 5760 x 3840) and divide those dimensions by your desired print resolution (like 300 DPI) and that gives you the maximum size printable. 5760x3840 = 19.2" x 12.8" - Never print an image from a 5D3 larger than this.


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## Malte_P (Jun 27, 2013)

STEMI_RN said:


> It just comes down to the print resolution. 300 DPI is the standard, but you can find printers that print even higher than that. The reason this becomes important is that you can't print (and still look good) at less than 300 dpi. So you have to look at the max resolution of the image (for a 5D3 that's 5760 x 3840) and divide those dimensions by your desired print resolution (like 300 DPI) and that gives you the maximum size printable. 5760x3840 = 19.2" x 12.8" - Never print an image from a 5D3 larger than this.



300 DPI is standard for print services.

inkjets have way higher DPI numbers (>5000 DPI) but then these are numbers for ink drops who make up a dot. so they are not really comparable with DPI numbers from other printer types.

the real resolution is lower then the 1440x5xxx DPI you see on some inkjets.




> The reason this becomes important is that you can't print (and still look good) at less than 300 dpi.



sorry but this is complete nonsense. wrong info you read all the time on the net.
get some infos about print resolution, viewing distance etc.

my advice, read "Harold Johnson - Mastering Digital Printing" and "Harold Johnson - 301 Inkjet Tips and Techniques".

you can print great looking images at 180 DPI.
it´s not the optimum.. but saying "you cant print good looking images below 300 DPI" is just wrong.

most people will not be able to see a difference between 240 and 300 DPI using a magnification glas.


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## docholliday (Jun 27, 2013)

On my 44" printer, I always try to aim for at least 300dpi (Canon/HP) or 360dpi (Epson) for "optimal" quality prints. These are the native engine sizes for the respective printers. However, viewing distance of the print determines how low you can go. A 30x40 print at 150dpi (about the lowest I'll do) looks about the same as a 300dpi print at 6'. However, if the viewing distance is closer (the view can walk right up to it), you'll probably want higher (>240/250dpi). If it's mounted behind a counter where the viewer is 10+ feet, you may even be able to cheat and drop that dpi down to 100dpi and get an acceptable print. Some billboards are printed as low as 5dpi.

For screen, 300dpi is usually overkill, it's best to try for 96dpi-120dpi to avoid any kind of interpolation artifacts. But, for screen, it really doesn't matter. The reason I drop low dpi to the web - in case somebody wants to swipe the image and try printing at home - the 96dpi low res image will fall apart.

The export CAN make a difference - 300 vs 400 dpi is how many dots per inch. If exported too low (try printing an exported RAW 96dpi 8x10 and then a 400dpi 8x10 from the same file), the output software/driver/engine will have to interpolate to make up the extra pixels needed and the pixels will virtually be "larger". This will reduce the perceptual gradation smoothness. But, there is a point where it is overkill.

Yes, some of the printers can go to 2880+dpi, but it's not necessary - it's mostly interpolated by the printer/driver to give fine detail. And, it'll slow the print down considerably. 600/720dpi is probably the max that most pro printers will do on output - and only on certain media. 

If you are exporting for further editing and printing out of a third party app, you'll usually want more resolution in case of any changes, i.e. export as large as possible so that there is no enlargement made throughout the edit chain.

It's more important to be concerned with the choice of output media (glossy is perceptually sharper than matte at the same resolution), accurate calibration (gamut!), and finishing (coatings, lamination).


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## Malte_P (Jun 27, 2013)

docholliday said:


> On my 44" printer, I always try to aim for at least 300dpi (Canon/HP) or 360dpi (Epson) for "optimal" quality prints.



jeff schewes says for the new epsons 720 DPI is the best setting.
if you have the pixels to reach this without upscaling.

there is a whole LL video about this, worth watching.




> The export CAN make a difference - 300 vs 400 dpi is how many dots per inch. If exported too low (try printing an exported RAW 96dpi 8x10 and then a 400dpi 8x10 from the same file), the output software/driver/engine will have to interpolate to make up the extra pixels needed and the pixels will virtually be "larger". This will reduce the perceptual gradation smoothness. But, there is a point where it is overkill.



correct me if im wrong but setting the DPI in LR will not RESAMPLE the image?!
so it doesn´t matter.

you can set PIXEL to 1920 pixels and change the DPI to whatever you want... LR will still export a 1920 pixel image. so it doesn´t really matter. you can still set the DPI when you actually going to PRINT the image.

i don´t know for sure because i only print from photoshop and i never use the DPI setting in LR´s export dialog.
but it should not resample the image i think. that´s what the PIXEL option is for.


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## duydaniel (Jun 27, 2013)

This is nice!!!
If I understand correctly,
The 5D3 has 5760 x 3840, so if I want to print a 30x20

I just divide 5760/30 = 192 dpi.
Then export the image should bea 192 dpi.


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## Malte_P (Jun 27, 2013)

duydaniel said:


> This is nice!!!
> If I understand correctly,
> The 5D3 has 5760 x 3840, so if I want to print a 30x20
> 
> ...



well the exported image usualy should have the MAXIMUM amount of pixels delivered from your camera.
you don´t downsample an image without a reason.

i am from europe so i don´t know the common print sizes in inch. 
if you want a common 10x15m print, your 5D MK3 delivers 975,36 DPI.
much more then a print lab needs.

if you say, i want to print 10x15cm in good quality, you can downsample (means you throw pixels away) an image and still print at 300 DPI. why would you do that, to save some harddisk space or to save bandwith when you upload.

your downsampled 5D MK3 image then has 1772x1181 pixels and would print 10x15cm at 300 DPI.

if you say 180 DPI are enough for a 10x15cm print you can downsample even further and make the image even smaller.

for 180 DPI and a 10x15cm print it is enough when the image has 1063x709 pixels.

or lets say you have an 4000x2000 pixel image.
you can print the 4000x2000 pixels at 300 DPI and have a 13,3x6,6 inch print.
or you can print the SAME 4000x2000 pixels at 180 DPI and have a 22,2x11,1inch print.

or you can say... i only want a 13,3x6,6 inch print at 180 DPI.
you then can and RESAMPLE the image to 2448x1197 pixels and save some space on your harddisk.

but you normaly want to preserve the maximum amout of pixels.
i do... 

from a logical point of view the DPI setting in the LR export dialog should not RESAMPLE an image.
it should not change the quality (amout of pixels) of the image.
it is only to tell what you think what size/quality the image should be printed at.


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## duydaniel (Jun 27, 2013)

Malte_P said:


> duydaniel said:
> 
> 
> > This is nice!!!
> ...



This seems to give a different ideas to previous posts I read.
Anyway, I just try to export an image (Canon 5D3) 23 megapixels to a 15000x10000 pixel image.
The result is quite incredible. It is a 15000x10000 image!!!

The 100% view is much larger than the original... I guess the resolution is still the same but they just split a pixel into smaller ones


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## Malte_P (Jun 27, 2013)

duydaniel said:


> Malte_P said:
> 
> 
> > duydaniel said:
> ...



you do that via RESAMPLING.
you interpolated the original image.

when you resample an 4000x2000 pixel image to 8000x4000, you doubled the amout of pixels in x and y direction.

when you save that resampled file it will have a much bigger filesize.

the resolution (*) of your image has changed.



> The 100% view is much larger than the original... I guess the resolution is still the same but they just split a pixel into smaller ones



pixels in an image have no defined size. they only get size via the output medium (monitor or print).
in layman terms, DPI tells the printer how big it should make a single image pixel on the output media.

so what you have done is, you have increased the number of pixels in your image.
as you monitor has a fixed number of pixels the 100% view will show a smaller part of the resampled image. 



(*) ps: 

resolution is defined as pixel per length unit (for example lines per mm is a resolution). 
"4000x2000 pixels" is not a resolution.. not by the definition of resolution.
because pixels in an image have no defined size.
it´s common to speak about megapixel resolution.. but per definition it is not.


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## RGF (Jun 27, 2013)

duydaniel said:


> This is nice!!!
> If I understand correctly,
> The 5D3 has 5760 x 3840, so if I want to print a 30x20
> 
> ...



If you export at 192 you get 20x30 inches. At 360 (which I have heard is best for most Epsom printers) you get something like 10x15. Either way the number of pixels is the same. In the end you will need to up res the Image to 20x30 at the desired print dpi. At this point it is all semantics


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## Malte_P (Jun 27, 2013)

some more infos here:

http://www.cambridgeincolour.com/tutorials/digital-camera-pixel.htm


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## DFM (Jun 27, 2013)

PPI (_Pixels _Per Inch, which are different from Dots Per Inch) will decide the number of pixels in the exported image _only_ if you set the Image Sizing measurement unit to inches or cm instead of pixels. If you stick to the default of pixels, it has no effect whatsoever. The only reason for showing physical units on that dialog is to help you do the math.

PPI is a tag in the JPEG header which tells third-party software how to calculate the "100%" physical size of the image, for example when placing it into another document or starting the page setup for a printout with "use actual size" selected. It doesn't affect image quality, sharpening, etc. in any way. In the attached 100% crop of some laser engraving, the left side was exported at 1200PPI and the right side at 12PPI (print sharpening enabled).

When printing from any pixel-based format, the image size (in pixels) and the scaling factor (in percent) are all that matter. If you export a 1000x1000 pixel JPEG file at 300PPI, and another one at 30PPI, then use 'fit to page' when printing, the result will be _identical_. However, drop them into a Word file and the second one will be zoomed like crazy.


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## docholliday (Jun 27, 2013)

Malte_P said:


> docholliday said:
> 
> 
> > On my 44" printer, I always try to aim for at least 300dpi (Canon/HP) or 360dpi (Epson) for "optimal" quality prints.
> ...



LR won't resample the image, but the printing app will a 1900px image at 100dpi will be 19" at native res. at 200dpi, it'll be 950px. If you set the 200dpi and still want 19", it'll have to interpolate an extra 950px into the image to make it work (or print the existing pixels at twice their size).

So, yes, it does matter.

With the Epson printers - it depends on what the NATIVE resolution of the print engine is. If it's a 720x360 engine, then 360 would be the default. If it's a 720x720 engine (or 1440x720), it'd be 720dpi. I've printed stuff as low as 100dpi on a 60" print and looked great displayed. Nobody who viewed it knew how low the resolution was. Of course, it was mounted in a gallery where the viewers couldn't get closer than about 15' from it (over a balcony on the other side wall).


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## Pi (Jun 27, 2013)

DFM said:


> PPI (_Pixels _Per Inch, which are different from Dots Per Inch) will decide the number of pixels in the exported image _only_ if you set the Image Sizing measurement unit to inches or cm instead of pixels. If you stick to the default of pixels, it has no effect whatsoever. The only reason for showing physical units on that dialog is to help you do the math.
> 
> PPI is a tag in the JPEG header which tells third-party software how to calculate the "100%" physical size of the image, for example when placing it into another document or starting the page setup for a printout with "use actual size" selected. It doesn't affect image quality, sharpening, etc. in any way. In the attached 100% crop of some laser engraving, the left side was exported at 1200PPI and the right side at 12PPI (print sharpening enabled).
> 
> When printing from any pixel-based format, the image size (in pixels) and the scaling factor (in percent) are all that matter. If you export a 1000x1000 pixel JPEG file at 300PPI, and another one at 30PPI, then use 'fit to page' when printing, the result will be _identical_. However, drop them into a Word file and the second one will be zoomed like crazy.



+1
Bottom line, ignore the DPI. It has very specific applications, and you will likely not need to worry about them.


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## Malte_P (Jun 27, 2013)

docholliday said:


> Malte_P said:
> 
> 
> > docholliday said:
> ...



it doesn´t matter what DPI you set in LR as long as you make the correct settings in the app you print with. it´s not an irreversible setting that alters the quality (like resampling)... that´s what i mean.



> > jeff schewes says for the *new * epsons 720 DPI is the best setting.
> 
> 
> 
> With the Epson printers - it depends on what the NATIVE resolution of the print engine is. If it's a 720x360 engine, then 360 would be the default.



yes and the new espons should have 720DPI.


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## CarlTN (Jun 29, 2013)

This is an interesting thread full of great info.

I must disagree that you can never print anything larger than the native resolution at say 300 dpi. I have had a 20x30 inch print done from a mere 15MP camera, which I scaled using only CS5 (I have since bought the Perfect photo suite 7, which works even better for enlargements). The resolution of the final jpeg I sent to the printer, was a 20x30 inch image at 300 dpi. You can get less than 1 foot from the print and it looks sharp. Of course the image was maximally sharp to begin with. But just because the native resolution of the camera was far lower than this, does not mean the print is not sharp...let alone not even useful. The client must have been happy with it, because it is hanging in the lobby.


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## barfbaggs (Jul 3, 2013)

I spent 20 years in commercial printing and prepress, and can tell you that the general rule is that an image printed at 100% size should have a dpi of twice what the line screen is that your printer will be using. The printer you select will generally ask you to select the line screen (ls), or provide you with what their standard is. Most standard magazines are printed at 133ls, 150ls and 175ls, so for an image printed at those line screens, you would optimally need 266dpi, 300dpi, and 350dpi respectivley. Higher end publications are generally printed at 200ls to 300ls, with those requiring dpi's of 400 and 600 respectively. All of our proofing on large format Epsons is processed using those same files with the same settings. To sum it up, use a dpi of twice the line screen to print at 100%. 10% less than double will likely be unnoticeable, and anything more than double does not hurt but may add slightly to file processing times.


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## Pi (Jul 4, 2013)

I believe that many posts miss the OP's point. DPI in LR just writes a flag in the EXIF, and _it is not_ used as a basis for resizing the image. For most practical purposes, that flag is completely irrelevant.


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## duydaniel (Jul 7, 2013)

Pi said:


> I believe that many posts miss the OP's point. DPI in LR just writes a flag in the EXIF, and _it is not_ used as a basis for resizing the image. For most practical purposes, that flag is completely irrelevant.



I have learned quite a lot!!!
Thank you guys


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