upsampling an image in photoshop

Sorry for being so thick but I would like to know the best way to

upsample an image in photoshop to get the best quality image

possible. I realize I can't upsample without some quality loss but

I would like to do the best I can.

My images load at pix dimension of 1200x1600.

image size is 22.22 inches by 16.667 inches and resolution is 72.

If I change size to 10 x 7.5 in., my resolution changes to 160.

how can I get a higher resolution or better quality image using just

photoshop. If I change my size to 11x14 what would be the maximum

resolution I could stretch my image to.

Also, is there another recomended program to do this without

breaking the bank. eg genuine fractals.

I appreciate any help

jerry

Hi Jerry. Photoshop's bicubic interpolation is about all you'll have to use unless you buy Genuine Fractals - which purports to do a better job. I've never used it so I can't comment personally. You don't have a whole lot of pixels to stretch there, but you can give it a shot. Open the image and select the image re-size screen. With the Resample Image box UN-checked, key in the lowest acceptable dpi you can live with. (This may take trial and error - I've heard that, as a rule of thumb, you don't want to go beneath 240 dpi; but that's not etched in granite - digital camera files supposedly interpolate better than film scans) Let's say you try 200 dpi. Now, CHECK the Resample Image box, and under Document Size, put in the dimensions you'd like for your print. Photoshop will then re-size it up for you. Whether you get pleasing results or not may depend on the image itself. If it's very sharp to begin with, you may be pleasantly surprised. There's an interesting article that might be of help in the April edition of Shutterbug Magazine called "A step By Step Guide For Big Prints From 35mm Film". I know you're not using film, but the technique that author Cris Daniels applies uses Corel Painter to smooth out the "jaggies" that often result from up-sampling should be useful for digital camera files too. Also keep in mind that a print that big won't be viewed too close-up. So it might look a little thin at arm's length, but at a viewing distance of 2 feet or so, it might be perfectly fine! I don't think there's a hard and fast rule to tell you what maximum resolution you can stretch your image to; you'll need to judge for yourself and it can vary greatly. Best wishes! ...Beau

I agree with Beau that Photoshop has all the tools you need to resize your image, but I want to suggest an alternative method of achieving it. Instead of performing your operation in one step, break it into a series of smaller steps. This method, called "Stair Interpolation", has been shown to permit increases in image size with less image degradation. In some tests, it produces better results than using a third-party solution.

 

Here's how to go about it:

 

Step #1 � Change printing resolution without changing actual pixels.

 

With your image open, go to Image|Image Size. Make sure that �Constrain Proportions" is checked and that �Resample Image� utilizes Bicubic interpolation. Ignore the Pixel Dimensions panel entirely. For Document Size, enter a Width of 100, and change the measurement box from inches (or whatever) to �Percent�. On the next line, leave Height unchanged. �Constrain Proportions� will automatically calculate this--very important if you are going to save this as an action. Enter your desired printing resolution: e.g., 240, 300, 360, etc.--and click OK. What you have done is to change your print resolution settings without actually affecting the pixels within the image. (This can be recorded as an action if you are going to do it frequently.)

 

Step #2 � Perform a Stair Interpolation.

 

Perform exactly the same steps as above, but instead of 100% under width, enter 110%. Press Okay. What you have done is to increase your image size by 10%. (This can be recorded as an action if you are going to do it frequently.)

 

Step #3 � Check the new dimensions of your image. If you need to resize, repeat Step #2. Do this as many times as you need to get ALMOST to your final desired output. (If you commonly resize images by a given number of stairs, you can copy the action you made under #2 the required number of times, producing one action that takes all the stairs in progression.)

 

Step #4 � When almost at your final desired dimension, either perform one last resize or do your final reinterpolation through the crop tool, setting the final desired dimensions in the dialogue box. Be careful to leave your resolution where you set it in step #1. Either way, you can make this part of the master action you created in Step #3.

 

The resulting image takes a bit more time than resizing in one massive operation, but I think you'll find the results worth it.

 

Good luck!

If you're images are coming from a digital camera (and with dimensions of

1200 x 1600, I assume they are) and you're trying to print at 11 x 14 inches, I'd

suggest you first try printing at a lower resolution rather than upsampling your

images. Especially if you're shooting in RAW or TIFF mode.

 

A digital camera with a decent lens is going to give you a higher quality digital

image than a scanned slide/neg at the same resolution -- no noise, grain, etc.

You might be surprised at how good a 108 ppi/dpi printed image can look.

great suggestions everyone / O am really thnakful and excited about trying these techniques.

jerry

<I>Hi Jerry. Photoshop's bicubic interpolation is about all you'll have to use unless you buy Genuine Fractals - which purports to do a better job.</I><P>There are two better interpolation schemes than the horribly overpriced genuine Fractals plug in.<P>

1.) Stair Interpolation 2.0 from <A HREF = http://www.fredmiranda.com/SI/index.html> http://www.fredmiranda.com/SI/index.html</A>. This is a Photoshop "Action" comprised on something like either 5% or 10% increment increases in size at the same resolution your file starts in plus a couple of other Photoshop image tweaks to smooth out the transition in file sizes or a better looking final image than genuine Fractals will produce. The cost is less than $20.00 for the action <P>The other interpolation tool that produces fine results is S-Spline from <A HREF = http://www.calumetphotographic.com> www.calumetphotographic.com</A> <P>As far as the maximum level of resolution at a given output size can be in Photoshop, i think that it is more important to consider what the destination is: inkjet/glicee print? Durst Lambda or Lightjet print or transparency? Worldwide web viewing? Magazine, brochure or book lithographic reproduction? Each kind of reproduction will have it's own needs and specifications.

ellis, the article at the fred miranda site you recommended is fantastic. It compares photoshop bicubic with Genuine fractals with his step interpolation program as well as S-pline . very convincing and at 15$ a real bargain . I will buy it today.

I've tried SAR Image Processor ( www.general-cathexis.com ) and compared it to the Stair Interpolation method, bicubic, Lanczos, etc. and prefer SAR using the Jensen-Xin Li hybrid method, which does a good job of edge enhancement while avoiding the patterning in smoother areas and jagginess in edges I see with the others. (See examples by clicking on "Edge Preserving Image Enlargement (Jensend Hybrids)".)

 

It only upsizes in powers of 2 - for in between, I upsize to larger, then downsize in Photoshop using bicubic. I've used it for printing wonderful 11x14's and am about to try my first 16x20 from a 2048x1536 original.

 

SAR is free to download and use, and only $20 for documentation to try parameters other than default. Try it and see what you think.

I just tried SAR as recommended in the previous post. Based on results of upsampling one (so far) tif image from 24 meg to 96 meg, I would say it is extremely good. It does require a lot of MIPS and RAM.

I have just finished writing a photoshop filter plugin that resizes images with a good algorithm. It's a filter plugin so you will resize you image directly into photoshop (or many other programs): no need to save to a file or similar.

I am looking for beta testers, so if you are intersted please send me an e-mail and I will be glad to send you a copy of the plugin.

 

Best regards

 

Fulvio Senore