Image sizing

[Bobobird]

I do not normally print much but do sometimes if friends want a pic or 2. Even then max size is usually a 12"x8" or a 12"x10".

A new birding friend were discussing some of the shots we had taken and he said he was going to print one at 45" on the wide end. That got me wondering how he could do that as the normal image in the RAW converter is much smaller.

That got me looking into the RAW converter settings for the colour space, dpi, bit depth, etc. I knew there was size option in there but never bothered using it leaving my shots whatever the default was.

So I took an unprocessed image and upped the default size of about 17 inches wide to 35 inches wide and processed that through the converter and opened that into PS6. I then redid the conversion without resizing and opened that into PS.

On my 27" monitor both images looked exactly the same. Without further processing I zoomed both to 100", entered full screen and viewed them from about 6 feet away. Again both looked exactly the same.

I was expecting substantial deterioration in the upsized version but have not.

What gives? or is my long held view about upsizing incorrect ?

That leads to another question - what if I had made the image 70 inches on the wide end? I could try it but prefer to see what everyone has to say first and put your expertise into play before going further with the exercise.

Thanks.

[DanK]

Just guessing: they look the same because they are both compressed to the resolution of your screen, which is probably 1920 x 1200 or less. could that be what is going on?

[Bobobird]

Thanks Dan.

So apart from actually printing the 2, there is not way to see the differences?

[Colin Southern]

Hi Bobo,

Without knowing the settings that you used, in most cases changing the size of the picture in ACR doesn't re-sample the image - it just changes the tag for resolution to compensate. eg supposing you have an image that's 6000px wide by 4000px high and your default settings say that this is 30 inches wide by 20 inches tall at 200PPI. If you change the size to be 60 inches with and 40 inches tall by default it'll do that for you, but to compensate for the increased size it's to be printed over it'll change the PPI to 100.

The thing to remember is that in either case the image is still 6000px x 4000px and thus will look exactly the same at 100% magnification.

There are ACR options for resampling the image but I STRONGLY suggest you stay WELL clear of them, as any changes you make stick as new defaults and if you set it lower and then forget about it then ALL future images will have information discarded and if you set it to up-sample then ALL future images will be much larger (but not contain any more useful information). Frankly, I wish Adobe would remove that option altogether.

To address your original issue - just print it - it'll look fine.

[Bobobird]

Thanks Colin - that is reassuring. Will do just that.

I have reset that sizing thing back to what is was by default after that experiment so should be fine. Will check again though when doing any image that nothing odd has happened.

[Colin Southern]

Thanks Colin - that is reassuring. Will do just that.

I have reset that sizing thing back to what is was by default after that experiment so should be fine. Will check again though when doing any image that nothing odd has happened.

You're very welcome.

I see that the PS CC version is a bit more advanced than some previous version (when I last looked), but from what I see now, providing that the resize option isn't ticked then you'll be safe.

In a nutshell, if resizing is needed then there's no real reason not to just do it in Photoshop rather than ACR. There are some who would up-sample the image in question to print at 300 PPI @ 45in, but personally, I wouldn't bother -- chances are all that will happen is that you'll end up with a huge file that will look exactly the same at normal viewing distances anyway (and probably no different up close either) (44" x 22" is the size I print at most often - "worst case" is I'll up-sample to 180 PPI)

[Bobobird]

Thanks for the additional info. Most useful. I do not intend to do this much anyway but good thing to have sitting at the back of the brain.

I am still on CS6 but will move to CC in a couple of days.

Just looked at the ACR upsized image. It is 431mb. That is huge.

I also just looked at the exif - the file is still at 300dpi.

[Colin Southern]

Thanks for the additional info. Most useful. I do not intend to do this much anyway but good thing to have sitting at the back of the brain.

I am still on CS6 but will move to CC in a couple of days.

Just looked at the ACR upsized image. It is 431mb. That is huge.

I also just looked at the exif - the file is still at 300dpi.

Yep - it will be huge - and yep, it'll keep the PPI the same when up-sampling unless told otherwise. The thing with PPI is though that - generally - it's a moot point because you can't actually do anything meaningful with it. The ONLY thing that really matters is the pixel dimensions.

Think of it this way - if the image is "X" pixels wide and "Y" pixels long then that's the amount of information contained in the image that you have to work with. If that works out to be 5000 PPI then "who cares" because our eyes won't be able to resolve that. If it works out to be 5 PPI in a (probably very large) print then our eyes certainly would be able to resolve the degradation, but what exactly would one do about it? (there's only so much information in the image and up-sampling doesn't suddenly & magically fit a sensor 1000 times as large to your camera and automatically re-shoot the exact same image for you so you get more information to work with).

In reality, all PPI tells us is "how good the image is likely to look up-close when printed at the specified size" (300+ = "perfect"; 180 -> 300 "great"; 100 -> 180 = "OK"; <100 = "marginal"), but event that is moot because the bigger the print the further back people view it from, and again, if they want to view a huge print up at a nose length away, there's nothing that can be done anyway because there's only so much info that the sensor captured; up-sampling doesn't add detail that wasn't captured in the first place. So as a rule of thumb, with a modern camera - providing the shot isn't excessively cropped - just print the darn images any size you like.

Generally with large prints people worry far too much - I do them all the time and I don't recall anyone ever complaining about loss of detail up close (only 1 was ever an issue and that was shot at VGA resolution (640 x 480 pixels) (and we had to crop it to around 320 x 480 -- cringe) - and even THAT looked OK printed 22 x 15 @ about 6 feet away!) -- which is about 1% of the desirable amount of information.

For the most part people worry about it far too much.

[Bobobird]

I will do one of a shot that should be printed. The "sample" here can be but if I am going to spend money on it might as well do the one from the recent comp.

Thanks Colin - always a great help. Much appreciated.