Resizing pictures for image libraries - resample?

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Itti

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Itti
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There are lots of threads on this already and I've worked out how to do it in Photoshop but I have a more specific question than that.

When I resize the image (under "image size") there's a tickbox at the bottom that asks me if I want to resample the image when I resize it. I have no idea what this is or if it's advisable.

And if I do want to do that, I have a further choice of bicubic, bilinear or nearest neighbour resampling, whatever the hell they are. Again, would appreciate advice.

Thanks very much!
 
If it is of Alamy etc, they suggest bicubic smoother, but tbh I find that Lightroom does a marginally better job and something like Genuine Fractals does a much better job, like night and day better.
 
If you're given the choice use RESAMPLE every time.

RESIZING the mage just resizes it while keeping the same number of pixels as the original, so particularly when upsizing, the image can soon appear very pixelated.

RESAMPLING means pixels will be added or removed to suit the new image size and maintain better image quality.
 
Okay, so I definitely want to resample then.

What about the bicubic/bilinear/nearest neighbour thing? One vote for bicubic so far, anyone else?! :D Does anyone know what they actually mean? :P
 
Generally speaking BICUBIC for upsizing and BILINEAR for downsizing, but just check the Help file on your particular package as the terms used do vary a bit.
 
Itti said:
Okay, so I definitely want to resample then.

What about the bicubic/bilinear/nearest neighbour thing? One vote for bicubic so far, anyone else?! :D Does anyone know what they actually mean? :P
Click to expand...

Just use Bicubic.

The new pixels are interpolated by averaging pixels in the same area.

Nearest neighbour just uses the nearest pixel, fast but low quality.
Bilinear uses 4 nearest pixels and calculates a weighted average, quite fast and a bit better quality.
Bicubic uses 16 nearest pixels and calculates a weighted average, a bit slower but the best quality.

Fast & slow are relative and with a modern computer you will not notice much difference.
 
CT said:
If you're given the choice use RESAMPLE every time.

RESIZING the mage just resizes it while keeping the same number of pixels as the original, so particularly when upsizing, the image can soon appear very pixelated.

RESAMPLING means pixels will be added or removed to suit the new image size and maintain better image quality.
Click to expand...

Is that the right way round CT? How can you gety better image quality by adding random pixels?

If I can get an image size I need without resampling, I don't do it. Adding pixels gives poorer IQ - ixelated images only generally happens when upsizing small images by a large amount.

Obviously this depends on exactly what you are doing with your images but as a general rule Resizing WILL provide better IQ. You don't need 300ppi to print large images.
 
If you're using Photoshop, then the recommendation is Bicubic Sharper for reducing and Bicubic Smoother for enlarging. I've tried Genuine Fractals, but to be honest, couldn't see any difference over Photoshop.
 
EOS_JD said:
Is that the right way round CT? How can you gety better image quality by adding random pixels?

If I can get an image size I need without resampling, I don't do it. Adding pixels gives poorer IQ - ixelated images only generally happens when upsizing small images by a large amount.

Obviously this depends on exactly what you are doing with your images but as a general rule Resizing WILL provide better IQ. You don't need 300ppi to print large images.
Click to expand...

But if you don't resample, your pictures will be low resolution and I don't imagine you will get the higher image size required for picture libraries either.
 
Somelier said:
If you're using Photoshop, then the recommendation is Bicubic Sharper for reducing and Bicubic Smoother for enlarging. I've tried Genuine Fractals, but to be honest, couldn't see any difference over Photoshop.
Click to expand...

I don't think I have these two options. (Using Photoshop 6.) It's just called bicubic.
 
The OP made it pretty clear he was talking about upsizing for image library submissions, which usually means 50mb and a considerable upsizing depending on what camera he's using.

Photoshop tutorial HERE
 
Itti said:
But if you don't resample, your pictures will be low resolution and I don't imagine you will get the higher image size required for picture libraries either.
Click to expand...

That is not necessarily true. What are you resizing from and to? If you already have a 10Mp image and you need to print larger, lower the ppi value. For printing large images you do not need to achieve 300ppi images - I print my A3+ images at 180ppi and you cannot tell the difference from an image resampled to 300ppi - why make your file so much bigger for no perceived benefit? I print some large images at 150ppi and again - almost no difference - hard to say which is better.

I appreciate if an image library requires a specific size that you will need to resample but for general use you should avoid resampling.
 
CT said:
The OP made it pretty clear he was talking about upsizing for image library submissions, which usually means 50mb and a considerable upsizing depending on what camera he's using.

Photoshop tutorial HERE
Click to expand...

CT - you're right :) I forgot the thread heading once I read the original posts! So yes if you need to resample for an image library yes.

But generally I'd advise against resampling - unless you have to. Even for printng you don't require 300ppi. You will see no difference even for small prints by printing at 240ppi and for larger images down to 150ppi - and lower!

You say that resampling provides better quality and that was the issue I saw..... i don't see how this would generally be the case and is quite a sweeping statement.
 
CT said:
The OP made it pretty clear he was talking about upsizing for image library submissions, which usually means 50mb and a considerable upsizing depending on what camera he's using.

Photoshop tutorial HERE
Click to expand...

Itti is my real name and I am a woman :razz:
 
EOS_JD said:
That is not necessarily true. What are you resizing from and to? If you already have a 10Mp image and you need to print larger, lower the ppi value. For printing large images you do not need to achieve 300ppi images - I print my A3+ images at 180ppi and you cannot tell the difference from an image resampled to 300ppi - why make your file so much bigger for no perceived benefit? I print some large images at 150ppi and again - almost no difference - hard to say which is better.
Click to expand...

From about 48MB to 50MB. (uncompressed size)

EOS_JD said:
I appreciate if an image library requires a specific size that you will need to resample but for general use you should avoid resampling.
Click to expand...

I wasn't talking about general use though was I? :thinking:
 
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