Resizing images

The Darkroom

Hello there, a friend of mine said that I can make 16x20s with my 16mp camera for print but I'm having a problem resizing the image. I noticed that in order to do it I'd have to up sample the image from the existing pixels and I want to know if the steps I am following from what I learned through youtube are correct.

here is what I am doing.

Image resize > turn sample box off > change resolution to either 240,270 or 300ppi > turn on sample box again, change height 16 and width 20 ( this also up samples the pixels around 20% ( I think ) ) and then thats it. Am I doing it correctly? because when I do this and look at both the original image and the duplicate resized image in photoshop the one I've resized looks a little squished on screen compared to original.

original pixels I am working in in Raw is 4608x3456

I would really appreaciate anyones feedback or advice.

DaireQuinlan

The aspect ratio of a 4608x3456 image is 1.3, aspect ratio of a 20x16 print is 1.25 so you'll have to crop the image to fit it into a 20x16 print. What you have to do is ... precisely nothing. Upload it to photobox or whatever service you're using, select a 20x16 print and 'crop to fit' or whatever option is available. Photobox allows you to interactively do this to make sure you get the crop you want. Alternatively print to a 21x16 print which has an almost identical aspect ratio.

The Darkroom

DaireQuinlan wrote: »

The aspect ratio of a 4608x3456 image is 1.3, aspect ratio of a 20x16 print is 1.25 so you'll have to crop the image to fit it into a 20x16 print. What you have to do is ... precisely nothing. Upload it to photobox or whatever service you're using, select a 20x16 print and 'crop to fit' or whatever option is available. Photobox allows you to interactively do this to make sure you get the crop you want. Alternatively print to a 21x16 print which has an almost identical aspect ratio.

Thank you Daire for your help. So what you're saying is that I leave the native file as is i.e 4608x3456 and just crop it to a 20x16 in photoshop cc using the crop tool?

DaireQuinlan

The Darkroom wrote: »

Thank you Daire for your help. So what you're saying is that I leave the native file as is i.e 4608x3456 and just crop it to a 20x16 in photoshop cc using the crop tool?

Sure, you can do that as well.

The Darkroom

DaireQuinlan wrote: »

Sure, you can do that as well.

Just clarify I'm talking Width 20 inches by 16 height inches not cm so do the rules you just explained still apply and I can go ahead and crop? am I still up sampling the image with the crop tool when I enter the 20x16? And finally am I ever throwing pixels away when I do this?

Kenny Logins

Don't up sample. Just crop to the correct aspect ratio. They'll print at ~230dpi, which is fine for wall mounting.

The Darkroom

Great I've just done it. I've cropped to 20x16 at 300ppi and image looks great . of all the youtube tutorials ive seen on this you guys explained in a couple of posts thanks very much.

When I went to image size I seen the pixels jumped from 4608x3546 to 6000 x 4800. Have I done this correctly or is that kind of jump in pixels not healthy for print quality?

DaireQuinlan

The Darkroom wrote: »

When I went to image size I seen the pixels jumped from 4608x3546 to 6000 x 4800. Have I done this correctly or is that kind of jump in pixels not healthy for print quality?

In the crop tool IIRC if you blank the DPI (or PPI) text box it won't resize it. It makes no difference either way. You're still putting effectively the same amount
of data onto the same size piece of paper.

Kenny Logins

The Darkroom wrote: »

Great I've just done it. I've cropped to 20x16 at 300ppi and image looks great . of all the youtube tutorials ive seen on this you guys explained in a couple of posts thanks very much.

When I went to image size I seen the pixels jumped from 4608x3546 to 6000 x 4800. Have I done this correctly or is that kind of jump in pixels not healthy for print quality?

You shouldn't be adding pixels, you should be taking some away!

TBH I wouldn't touch the image at all, as Daire has said above, just let the printers crop top and bottom to fit the frame. That's all you need to worry about. People often get caught up the whole dpi thing unnecessarily. Do nothing - the printer sets your dots to their inches. That's all.

Myksyk

If cropping in Photoshop and you don't want to lose pixels, uncheck the 'delete cropped pixels' box at the top (pretty sure it's set to that as standard anyway).

DaireQuinlan

Myksyk wrote: »

If cropping in Photoshop and you don't want to lose pixels, uncheck the 'delete cropped pixels' box at the top (pretty sure it's set to that as standard anyway).

how can you crop something and not lose pixels? Maybe I'm misunderstanding things here ...

magicbastarder

just googled it:

A better, more flexible and non-destructive way to work is to leave the Delete Cropped Pixels option unchecked. That way, Photoshop will keep the cropped pixels and simply hide them from view

Kenny Logins

Doesn't really matter if they're deleted or just hidden, they won't be printed either way.

flyingsnail

magicbastarder wrote: »

just googled it:

My understanding of that is all of the original is still contained within the PSD and can be reversed (Image - reveal all). It is a type of non destructive editing like in Lightroom but if you save it as anything other than PSD the crop is then permanent

The Darkroom

Its just someone told me that you can enlarge an image 20% more than it is and ive learned so far that with a 16mp camera you can go no bigger than 20x16 and so when I crop and then go to image>image size It is telling my pixels have jumped up a notch.

If I uncheck the delete cropped pixels will I see different when going to image size dialog box having now cropped it with this unchecked?

thanks everyone for the replies and help.

Kenny Logins

The Darkroom wrote: »

Its just someone told me that you can enlarge an image 20% more than it is and ive learned so far that with a 16mp camera you can go no bigger than 20x16 and so when I crop and then go to image>image size It is telling my pixels have jumped up a notch.

If I uncheck the delete cropped pixels will I see different when going to image size dialog box having now cropped it with this unchecked?

thanks everyone for the replies and help.

BTW, did you ask the printers what resolution they print 20x16 at? I bet it's probably as low as 150.

Seriously, do nothing, just print it (crop to frame).

The Darkroom

DaireQuinlan wrote: »

In the crop tool IIRC if you blank the DPI (or PPI) text box it won't resize it. It makes no difference either way. You're still putting effectively the same amount
of data onto the same size piece of paper.

Just tried that but then the PPI when I go to image size dialog box goes way below 240 to 216 res.

The Darkroom

Kenny Logins wrote: »

BTW, did you ask the printers what resolution they print 20x16 at? I bet it's probably as low as 150.

Seriously, do nothing, just print it (crop to frame).

thanks for your help kenny but another question I have is what if I am sending it to someone to digitally download via dropbox and they want it 20x16 and they live half way around the world? I cannot send them a full res file? so I would need to resize it? this resizing and sampling is giving me a headache haha.

DaireQuinlan

magicbastarder wrote: »

just googled it:

Oh right. That's kinda neat. I guess if you save as a jpg or something it'll only save out the uncropped portion

Kenny Logins

The Darkroom wrote: »

thanks for your help kenny but another question I have is what if I am sending it to someone to digitally download via dropbox and they want it 20x16 and they live half way around the world? I cannot send them a full res file? so I would need to resize it? this resizing and sampling is giving me a headache haha.

Just leave the file (jpeg) as it is. Whatever size it comes out of the camera (after editing).

Combining your pixels with their inches gives the ppi. The inches aren't your concern, only the pixels, so give them all that you have.

I work in digital print, and this is one area that always causes confusion. We recommend ignoring these details. We'll let you know if there aren't enough pixels for a sharp print at your chosen size, and that's all you need to worry about.

Kenny Logins

Just looking at Photobox, and for a 60x40 canvas they'll go as low as 1500 pixels long side. That's about 67 ppi, and probably looks fine from 1m away.


http://www.photobox.ie/content/quality-advice/resolutionguide

CabanSail

The pixels you have available will print at 216 ppi at the size you have specified, with a bit of the paper left blank if you don't crop. You can drop the ppi down lower than that and you will be OK.

300ppi is the standard which many stick to but have no idea why or where it comes from. The print resolution can be varied quite a bit depending on where it will be printed and how it will be viewed. With that file resolution you could have an image printed to fill a huge billboard as it will be designed to be viewed from a distance. If you are printing to canvas it is often a lot more tolerant of low resolution images.

tl/dr You have plenty of resolution for a 20"x16" print, cropped or whole.

Kenny Logins

CabanSail wrote: »

The pixels you have available will print at 216 ppi at the size you have specified, with a bit of the paper left blank if you don't crop. You can drop the ppi down lower than that and you will be OK.

300ppi is the standard which many stick to but have no idea why or where it comes from. The print resolution can be varied quite a bit depending on where it will be printed and how it will be viewed. With that file resolution you could have an image printed to fill a huge billboard as it will be designed to be viewed from a distance. If you are printing to canvas it is often a lot more tolerant of low resolution images.

tl/dr You have plenty of resolution for a 20"x16" print, cropped or whole.

I think 300 is something to do with the limitations of the human eye.

The Darkroom

Ok now I think we are getting somewhere. Ok so without going to crop tool I've simply went into image size and unchecked the resample box. From there I've changed the height to 16 which automatically protected my pixels ( to prevent interpolation ) and gave me 21.333 in width and then it resampled the resolution ( PPI ) to 216 which you guys say is ok. I think I've heard that anything under 200 should be avoided so I'm pretty safe with 216 right? and I didn't need to do the printers job. Have I done things correctly now?

Thank you all by the way for taking the time to help out.

The Darkroom

One more question....why not crop it myself? should I trust the printer to crop it for me? thats seems a bit mad.

CabanSail

Kenny Logins wrote: »

I think 300 is something to do with the limitations of the human eye.

Apparently the origin was from old drum scanners which had a fixed sample rate of 150 dpi and they did two passes per line which resulted in an output of 300 dpi. These machines have long since been retired, but their legacy carries on.

The Darkroom wrote: »

Ok now I think we are getting somewhere. Ok so without going to crop tool I've simply went into image size and unchecked the resample box. From there I've changed the height to 16 which automatically protected my pixels ( to prevent interpolation ) and gave me 21.333 in width and then it resampled the resolution ( PPI ) to 216 which you guys say is ok. I think I've heard that anything under 200 should be avoided so I'm pretty safe with 216 right? and I didn't need to do the printers job. Have I done things correctly now?

Thank you all by the way for taking the time to help out.

You will be fine doing that. You can drop the dpi lower but worth being careful of the prints intention when it gets lower than about 150 (or so)

Kenny Logins

The Darkroom wrote: »

One more question....why not crop it myself? should I trust the printer to crop it for me? thats seems a bit mad.

...because the printer will know better than you. :pac:

You're really over-thinking this. Forget ppi and dpi. Crop the canvas to 4320 on long side and you're done.

If you don't believe me, create two new PSDs, one 2000 x 1600 @ 72 dpi and the other 2000 x 1600 @ 300 dpi.

They are the same. They are both 2000 pixels x 1600 pixels. The inches only exist on paper.

The Darkroom

CabanSail wrote: »

Apparently the origin was from old drum scanners which had a fixed sample rate of 150 dpi and they did two passes per line which resulted in an output of 300 dpi. These machines have long since been retired, but their legacy carries on.



You will be fine doing that. You can drop the dpi lower but worth being careful of the prints intention when it gets lower than about 150 (or so)

Ok I noticed you used ''DPI'' and not ''PPI''? when I do what I do in the image resizing dialog box in photoshop cc its Pixels per inch not dots per inch ( as would be on a printer right? ) eek. :eek: anyways hope I am ticking all the right boxes here and have finally got it right with my previous post and description of what I did.

I am not going to be printing it myself. I am resizing it for someone to download and to take to a commercial printer themselves.

CabanSail

DPI and PPI are more or less the same thing. PPI is used for a screen and DPI for a printer. Pixels vs dots, but each pixel will become a dot on a print assuming the device is capable of it.

magicbastarder

CabanSail wrote: »

DPI and PPI are more or less the same thing. PPI is used for a screen and DPI for a printer.

HOWEVER - if you have been sold PPI, you may be entitled to a refund. Mr. Brookes in Huddersfield received £600 compensation - why don't you check?

magicbastarder

that was lame.