Guidance - Resize or Crop

[ctsnowfighter]

Shooting at full resolution 6940 x 4640

Typically I crop to 9 x 7 Inches resulting in 580 pixels?

If I resize to 12 x 9 without resample it results in 580 pixels.

Which is best way to end up with 9 x 7 at highest quality when cropped for the subject?

I shoot a lot of wildfowl and even with cropped sensor and 400 mm it is not always close enough.

I end up with 

Thanks

cts

[D Fosse]

First of all, forget all about inches and ppi. It's irrelevant at this point and will just confuse the issue.

The image is just pixels. All the rest can be sorted later - if you need it. The image itself doesn't have a size, and it doesn't have a ppi value. It's just pixels.

So the question is - will you just crop the image as is, or are you aiming to upsample? If the latter, you have to be very clear on why you would want to do that. Upsampling never improves anything - on the contrary; quality will always suffer a bit. The question is how much. The only reason you ever want to upsample, is to avoid visible pixels.

If you just crop as is, anything above, say, 4000 pixels long side will still be a perfectly useable image for most practical purposes.

If you decide that you do need to upsample for whatever reason, you get the best result by doing this at the raw stage, using the AI-based "Super Resolution" in ACR/Lightroom. This doubles the linear pixel count. This is superior to any other upsampling method. It doesn't improve anything, but the quality degradation is less than any other method in Photoshop.

[ctsnowfighter]

Thank You, 

I would not need to Resize/resample before using Crop to "cut" to the bird in the center of the frame as example and retain quality.   I hope I understand correctly and do appreciate the guidance.  (resize/resample  or crop have the same effects upon the image ?  Therefore there is no need in doing both?)

I attempted to show the duck in the center of the photo that I would like to fill a 9 x 7 print size and yet retain the best image possible.  Hope this helps clarify my intentions.  

[D Fosse]

No, resize and crop are not the same thing. Again, you need to think in pixels. "Size" has no meaning here. You deal with that later.

First crop to the area you want, and then decide if there are enough pixels left to produce a decent image.

Now we can look at the ppi number, which is a measure of pixel density on paper. The ppi number defines the print size. It's a simple formula: pixels per inch. Setting a ppi number produces a certain print size, according to that formula. The higher the pixel density, the ppi number, the smaller the print, and vice versa.

Print requires a pixel density somewhere around 200 - 300 ppi, depending on circumstances. Higher than 300 is usually wasted.

You could do all these calculations yourself, but you don't need to. You can just input the numbers in Photoshop's Image Size dialog, and it calculates for you.

Just make sure "resample" is unchecked. If you check that box, the image is resampled using the ppi number as a guide. You normally don't want that.

If you do need to upsample, do it with "Super Resolution" in ACR or Lightroom. Again, it won't improve anything, but if you send out for print they may not accept it if the pixel dimensions are to small for the required print size.

[ctsnowfighter]

Thank You for the explanations and help.

PS is a challenge to me, never have had any training other than the web and books, all self taught. Began with CS3

CTS

[mglush]

Hi!

Here is a suggestion for creating the size and desired resolution for a file that I use on a regular basis. I first create a blank Photoshop document at the size (in inches) and resolution that I want to produce. Because I have to process multiple photos and crop them to the same size, I just open the photos and drag them into this file into layers. Then I can reposition them to focus on the area i want, and I have a photo that is the right size and resolution for what I need. I also use the Export feature "From Layers to Files" to do a batch process export.

Having a pre-set up file that I know will print correctly has been a real help.

Michelle