Changing resolution in Photoshop without recompressing img?

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Changing resolution in Photoshop without recompressing img?

Postby gpsmikey » Wed Dec 22, 2010 9:46 pm

OK, I have run into some interesting side effects of my cropping in Photoshop CS5. I had set the crop ratio for the crop tool to 1100 by 800 inches (I was thinking pixels or something) since I was only interested in the ratio (I thought). Turns out there are a couple of side effects - #1 is that with a image that is 1100 inches wide, at normal camera image resolutions, that ends up setting the resolution of the image to about 3 pixels/inch. That screws up things when you try to add text to the image. If I go into Image -> Image Size and set the resolution to 300 ppi for example (with the "resample" UNCHECKED so it doesn't change the number of pixels), when I save the image again (with no other changes), the file size has changed. Not a lot, but it has changed by 5 or 10 kb telling me that Photoshop is re-compressing the image again. Anybody know how to change that "resolution" setting in a jpg file without having it recompressed again?????

I *hate* being "helped" :evil:


mikey
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mikey (PSP6, Photoshop CS6, Vegas Pro 14, Acid 7, BluffTitler, Nikon D300s, D810)
Lots of PIC and Arduino microprocessor stuff too !!

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Re: Changing resolution in Photoshop without recompressing img?

Postby gpsmikey » Wed Dec 22, 2010 11:03 pm

As a follow-up, I have found some additional information that may be of use to folks - it seems with CS5, Photoshop has abandoned the JFIF tag for resolution and is using the EXIF resolution tags. What this means is that older apps like Corel that people are importing their images into suddenly starting with CS5 don't know what the resolution of the image is (here is a link that discusses that issue)
http://forums.adobe.com/thread/651179?d ... hread=true

The nice thing about standards is that there are so many to choose from ... :twisted:

mikey
You can't have too many gadgets or too much disk space !!
mikey (PSP6, Photoshop CS6, Vegas Pro 14, Acid 7, BluffTitler, Nikon D300s, D810)
Lots of PIC and Arduino microprocessor stuff too !!

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Re: Changing resolution in Photoshop without recompressing img?

Postby gpsmikey » Thu Dec 23, 2010 8:52 am

OK, for others that run into this issue, I (with the help of another person :D ) found a work-around that solves the problem. The correct solution is to manage to have the resolution setting correct in the first place, but if that is screwed up, the work around that is actually a good setting anyway ... is to go into your prefs in Photoshop (clt-k) and under the "Units and Rulers" change the setting for type to "pixels" instead of "points" - text will now be created based on the pixel size of the image instead of the resolution settings. While this does not completely solve the problem (Photoshop wants to limit you to 42 pixels max on the type), it makes it a workable solution - best solution is still to get the resolution setting correct in the first place. See below:

Image

The downside of this is Photoshop (at least in CS5) apparently has a limit on the size text you can have in pixels - see this screenshot from when I have it set to pixels and try to set the text size to 120 pixels ... best solution ??
GET THE RESOLUTION SET RIGHT TO START WITH!!

Image

Hope this helps someone else :D
You can't have too many gadgets or too much disk space !!
mikey (PSP6, Photoshop CS6, Vegas Pro 14, Acid 7, BluffTitler, Nikon D300s, D810)
Lots of PIC and Arduino microprocessor stuff too !!

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Re: Changing resolution in Photoshop without recompressing img?

Postby juicedownload » Thu Dec 23, 2010 4:19 pm

Mikey,

I've noticed when I have multiple layers and I resize one of the layer images to a smaller size, then when I later decide to make it large again the quality suffers for that layer image. Is this related to what you mentioned?

Tim

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Re: Changing resolution in Photoshop without recompressing img?

Postby gpsmikey » Thu Dec 23, 2010 5:39 pm

Hi Tim - no, that is a different issue. When you resize a layer down, it is resampled and you lose pixel information (unless you have converted it into a smart object which protects it from that). This is a case of the image data itself (number of pixels total) remains the same, but the "resolution" number gets changed which can affect how printing software handles the image as well as a number of other things that seem to pop up :shock: In my case, the pixels are not being resampled, only the scale factor for printing was changed (with some unfortunate consequences for me).

mikey
You can't have too many gadgets or too much disk space !!
mikey (PSP6, Photoshop CS6, Vegas Pro 14, Acid 7, BluffTitler, Nikon D300s, D810)
Lots of PIC and Arduino microprocessor stuff too !!

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Re: Changing resolution in Photoshop without recompressing img?

Postby juicedownload » Thu Dec 23, 2010 6:03 pm

Ah, thanks for the reply Mikey. I guess I will try making smart objects when needed.



Tim

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Re: Changing resolution in Photoshop without recompressing img?

Postby gpsmikey » Thu Dec 23, 2010 7:53 pm

Yeah, the "loss" does not actually happen until you actually "accept" the transform with a regular layer. With a smart object, it retains it's information - you can shrink it down to a small square, accept it, then resize it up huge and all the original info is still there (at least that is my understanding from watching Deke on Lynda.com :D -- I have not played with them much myself).

mikey
You can't have too many gadgets or too much disk space !!
mikey (PSP6, Photoshop CS6, Vegas Pro 14, Acid 7, BluffTitler, Nikon D300s, D810)
Lots of PIC and Arduino microprocessor stuff too !!

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