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07/26/2002 09:27:38 PM · #1 |
I read the thread that KD Johnson started on this subject and also the suggested Agfa link and I'm still confused (I would have posted this at that thread but sometimes I'm having trouble finding stuff in these forums).
To keep it simple, let's not talk for now about print but only about a 640x480 submission for dpc.
I have an image 1280px x 960px (highest res. on my Mavica) and I resize that to 640x480. In that case I'm not really resizing but resampling because I squeeze the 1280 px into 640 px and the 960 into 480 and Photoshop is making some calculations which pixels to alter. Correct? (On the Image size dialog Photoshop says I'm resampling).
Now, with that same 1280px x 960px I use the crop tool that I have specified to 640px and 480px and I select the rectangle of the specified size on my image. In that case, I'm resizing. Correct? If the image were on hard print, it would be like cutting off the extra pixels with a pair of scissors and the pixels that I selected in the 640x480 rectangle have not changed in any way. Correct?
Besides the opportunity for giving yourself room to crop out unwanted elements that you get from shooting the img in a bigger resolution, do you get a better end result from resampling to 640x480 as opposed to starting out with 640 x 480? In other words, is an 1280x960 img resized to 640 x 480 sharper than the same img that you shot at 640px x 480px to begin with? |
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07/26/2002 09:42:16 PM · #2 |
Originally posted by Journey:
I read the thread that KD Johnson started on this subject and also the suggested Agfa link and I''m still confused (I would have posted this at that thread but sometimes I''m having trouble finding stuff in these forums).
To keep it simple, let''s not talk for now about print but only about a 640x480 submission for dpc.
I have an image 1280px x 960px (highest res. on my Mavica) and I resize that to 640x480. In that case I''m not really resizing but resampling because I squeeze the 1280 px into 640 px and the 960 into 480 and Photoshop is making some calculations which pixels to alter. Correct? (On the Image size dialog Photoshop says I''m resampling).
Yes, and since you are resampling to exactly half the number of pixels you should get a pretty accurate result.
Now, with that same 1280px x 960px I use the crop tool that I have specified to 640px and 480px and I select the rectangle of the specified size on my image. In that case, I''m resizing. Correct? If the image were on hard print, it would be like cutting off the extra pixels with a pair of scissors and the pixels that I selected in the 640x480 rectangle have not changed in any way. Correct?
Not necessarily. You are probably re-sampling anyway, unless you drag the crop marquee to exactly include 640x480. If you drag the crop marquee over (say) 960x720 pixels, you will both "throw away" those outside the marquee, and re-sample those within it by a factor of 1.5. To just crop you must DESELECT the "fixed size" option on he crop tool, set your preferences to show pixels as the measurement units, and then drag the crop marquee while checking the dimensions in the INFO window until you have the correct size.
To ONLY resize you have to use the Image Size command, uncheck the resample box, and then change either dimension or the resolution (dpi) and the other values will change accordingly.[/i]
Besides the opportunity for giving yourself room to crop out unwanted elements that you get from shooting the img in a bigger resolution, do you get a better end result from resampling to 640x480 as opposed to starting out with 640 x 480? In other words, is an 1280x960 img resized to 640 x 480 sharper than the same img that you shot at 640px x 480px to begin with?
I always shoot the largest size and then crop/resample in one operation (DO use the "Fixed size" crop option). If you shoot at 640x480 you are essentially letting the camera do the resampling internally; I''d rather see what happens to it (in Photoshop). Also, if you never capture those extra pixels, you will never have the option of printing a larger size.
--Paul
* This message has been edited by the author on 7/26/2002 9:45:04 PM. |
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07/26/2002 10:10:16 PM · #3 |
Originally posted by GeneralE:
To ONLY resize you have to use the Image Size command, uncheck the resample box, and then change either dimension or the resolution (dpi) and the other values will change accordingly.
That''s exactly what''s confusing me!!! In the Image Size command when I uncheck Resampling there''s nothing I can do but change the document size in inches, percent. When I change the dimensions of the Document Size to 8.8888 and 6.6666 inches, it automatically changes the resolution from 72 to 144. ???? That''s resizing?]
Yes, I shoot in the highest size I can to have room to play with.
* This message has been edited by the author on 7/26/2002 10:12:10 PM. |
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07/26/2002 10:12:10 PM · #4 |
In not sure if I'm doing it right. First I do shoot at a high res.(1600x1200 or higher).
Then I take the image (in photoshop)and crop it until it is the look I desire.
Then I go to save for the web. I go to the image size and change the #s to 640x480. If the image is still to large a file(it usually is) so I lower the quality until it is 150 or less.
Am I doing it right or wrong? |
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07/26/2002 10:18:25 PM · #5 |
Hi Terry. No, I "think" you''re resampling. I thought I was resizing when I was really resampling. You better read the General''s response carefully because the answer is in it.
BTW, General, I did figure out that when you spec the crop tool to 640x480 you are not necessarily just resizing because it depends on the rectangle you select. Thanks, THANKS for the info window tidbit because that''s the key to resizing!!! You know, I use that info window more and more for more and more stuff.
This really was an area of confusion to me and I believe to others as well.
* This message has been edited by the author on 7/26/2002 10:18:37 PM. |
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07/26/2002 10:27:22 PM · #6 |
O K , you have managed to confuse me further. Whether I''m sesizing or resampling (I''ll have to go look those up) am I doing the right thing to keep my photo at the best quality for upload? It looks good - I actually just submitted my photo (it feels so good to have that done), and from what I could see, the quality looks good(better than my last one).
Maybe General will come back and answer this one?
(But in slow clear understandable language)
* This message has been edited by the author on 7/26/2002 10:28:07 PM. |
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07/26/2002 10:28:08 PM · #7 |
Originally posted by TerryGee:
In not sure if I'm doing it right. First I do shoot at a high res.(1600x1200 or higher).
Then I take the image (in photoshop)and crop it until it is the look I desire.
Then I go to save for the web. I go to the image size and change the #s to 640x480. If the image is still to large a file(it usually is) so I lower the quality until it is 150 or less.
Am I doing it right or wrong?
If the "fixed size" option is UNCHECKED when you first crop, you are doing it OK, just in two steps instead of one. A 640x480 image in 24-bit RGB mode is 900k (try saving in TIFF mode). You can use compression to lower the number of bytes on disk, but the file is then uncompressed when viewed or printed. That's one reason it may take longer to print a small JPEG than it does to print a larger TIFF version of the same image. Incidentally, native Photoshop format (.PSD) includes proprietary compression, which is why they may seem to be odd sizes (in bytes) compared to the TIFF file. |
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07/26/2002 10:35:20 PM · #8 |
RESAMPLE: The number of pixels changes. The "physical dimensions" will change, but the resolution (dpi or ppi) does not.
RESIZE: The number of pixels remains the same, but the physical dimensions and resolution both change.
It is possible to do both at the same time in the image size dialog. I will prepare some examples off-line and post them in a day or two... |
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07/26/2002 10:51:34 PM · #9 |
Originally posted by TerryGee:
In not sure if I'm doing it right. First I do shoot at a high res.(1600x1200 or higher).
Then I take the image (in photoshop)and crop it until it is the look I desire.
Then I go to save for the web. I go to the image size and change the #s to 640x480. If the image is still to large a file(it usually is) so I lower the quality until it is 150 or less.
Am I doing it right or wrong?
Terry, apologies for confusing you further. If the General says you're doing it right, you must be doing it right! And I'm just dead wrong. BUT, when I read your message and you say that you "crop it until it is the look I desire" and then you change lateron the #s to 640x480, doesn't that imply that some resampling is happening somewhere in this 2 step process???? Perhaps I'm just having a huge mental block on this one. Will need to wait for the examples that GeneralE is kindly offering. Thank you, Paul, for your kindness.
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07/26/2002 10:55:15 PM · #10 |
I am pretty sure that if you first make it 640x480 and then crop it, would would further reduce the quality.
( Watch, I'm probably wrong ) |
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07/26/2002 10:59:14 PM · #11 |
| GeneralE is the God of commercial graphics. Trust him, He's one of the best. |
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07/26/2002 11:03:53 PM · #12 |
Originally posted by TerryGee:
I am pretty sure that if you first make it 640x480 and then crop it, would would further reduce the quality.
( Watch, I'm probably wrong )
No, no, that's not what I meant. Perhaps I'm just confusing myself and everybody else wasting their time reading my posts out of semantics. Never mind me :)
I think I'm going to pull some weeds out of the garden to do something productive today for a change :)
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