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Photoshop and Changing Resolution ?
I am wondering if changing resolution from the camera default of say 180 to 200 or more would degrade the picture quality for printing ? .

If so, is there a way to do this ? I am trying to fit the requirement for Alamy of 45 megapixels from 6 megapixels camera ??? Is that possible ? advisable to do ? .

Thanks heaps in advance.

Be a torch bearer ...S3 IS..

Comments (15)

Peacewarrior wrote:.

I am wondering if changing resolution from the camera default of say180 to 200 or more would degrade the picture quality for printing ? .

If so, is there a way to do this ? I am trying to fit the requirementfor Alamy of 45 megapixels from 6 megapixels camera ??? Is thatpossible ? advisable to do ? .

I am not sure if the 45mp requirement that you mentioned is really true. Not much digital camera can produce this resolution in one capture....

I visited the Alamy website, it seems that their requirement is 48Mbytes uncompressed image. If you are using 24-bit RGB, this should translate to 48/3=16 megapixels..

If you try to enlarge a 6 megapixels image to 16 megapixels image, the extra pixels are obtain by interpolation. This most likely will not pass their quality control. They said they will reject images for "interpolation artifacts"..

The website that I visited is this, not sure if this is the one you mentioned:http://www.alamy.com/stock-photography-guide.asp..

Comment #1

Skylark_khur wrote:.

Peacewarrior wrote:.

I am wondering if changing resolution from the camera default of say180 to 200 or more would degrade the picture quality for printing ? .

If so, is there a way to do this ? I am trying to fit the requirementfor Alamy of 45 megapixels from 6 megapixels camera ??? Is thatpossible ? advisable to do ? .

I am not sure if the 45mp requirement that you mentioned is reallytrue. Not much digital camera can produce this resolution in onecapture....

I visited the Alamy website, it seems that their requirement is48Mbytes uncompressed image. If you are using 24-bit RGB, thisshould translate to 48/3=16 megapixels..

If you try to enlarge a 6 megapixels image to 16 megapixels image,the extra pixels are obtain by interpolation. This most likely willnot pass their quality control. They said they will reject imagesfor "interpolation artifacts"..

The website that I visited is this, not sure if this is the one youmentioned:http://www.alamy.com/stock-photography-guide.asp.

Be a torch bearer ...S3 IS.

Thanks for that. It seems I may not be able to submit to them at this stage. I have to wait till I get my 450D then ..

I just remember from another post. Thanks for the link...

Comment #2

I am wondering why the DPI is set at 120 or less when the picture is shot with 6 megapixels resolution ? .

Is it a set up in PS 7 or the camera actually ? A bit confused..

What do you recommend ? .

Thanks.

Be a torch bearer ...S3 IS..

Comment #3

Peacewarrior wrote:.

I am wondering why the DPI is set at 120 or less when the picture isshot with 6 megapixels resolution ? .

Is it a set up in PS 7 or the camera actually ? A bit confused..

Sometimes some softwares misread the EXIF data. There are usually a thumbnail embedded in a JPEG. The resolution of this thumbnail are usually set to somewhere within the monitor dpi. For example, for my 8MP photos, the thumbnail is 72dpi but the printing is set to 480dpi..

I guess the 120dpi should be the thumbnail dpi. Most monitor nowadays are from 100~120dpi. Older low resolution monitors is about 72dpi..

Anyway, photo is usually printed at 300dpi and above. Some manufacturer will tell you that you can print at much larger size at about 150dpi but these are usually for viewing from further distance, not for something to view handheld...

Comment #4

Thanks for the response..

I wonder if you then adjust the image size using bicubic to 300 dpi ??? It would somehow adjust the dimension of pixels..

What I am wondering is this ? how do you save your jpeg files or tiff in that matter ? Since PS 7 does not show a reasonable DPI, do you manually adjusting it ? .

Thanks in advance ....

Skylark_khur wrote:.

Peacewarrior wrote:.

I am wondering why the DPI is set at 120 or less when the picture isshot with 6 megapixels resolution ? .

Is it a set up in PS 7 or the camera actually ? A bit confused..

Sometimes some softwares misread the EXIF data. There are usually athumbnail embedded in a JPEG. The resolution of this thumbnail areusually set to somewhere within the monitor dpi. For example, for my8MP photos, the thumbnail is 72dpi but the printing is set to 480dpi..

I guess the 120dpi should be the thumbnail dpi. Most monitornowadays are from 100~120dpi. Older low resolution monitors is about72dpi..

Anyway, photo is usually printed at 300dpi and above. Somemanufacturer will tell you that you can print at much larger size atabout 150dpi but these are usually for viewing from further distance,not for something to view handheld..

Be a torch bearer ...S3 IS..

Comment #5

Peacewarrior wrote:.

Thanks for the response..

I wonder if you then adjust the image size using bicubic to 300 dpi??? It would somehow adjust the dimension of pixels..

What I am wondering is this ? how do you save your jpeg files or tiffin that matter ? Since PS 7 does not show a reasonable DPI, do youmanually adjusting it ? .

No, you shouldn't change the dpi in the image setting if it read wrongly. By doing so it will enlarge the photo by interpolation (bicubic is one kind of interpolation algorithm). You get bigger file size without really getting more details..

It doesn't actually matter if the setting shows 120dpi as this setting only tell the DEFAULT printing resolution, you still can print at any other size and resolution. For easy calculation, if I assume 6megapixels is 3000x2000 and you print your photo at 6"x4", the printing resolution will be 3000/6=500dpi > more than enough. If you print at 10"x8", you need to crop your image to 2500x2000 and the printing resolution will be 250dpi > still barely acceptable as photo..

I don't know if there is a way to adjust the default DPI without changing all other things in PS 7. But the default dpi shouldn't bother you as it only tell you the default printing size > and we seldom print at this printing size...

Comment #6

Peacewarrior wrote:.

Thanks for the response..

I wonder if you then adjust the image size using bicubic to 300 dpi??? It would somehow adjust the dimension of pixels..

What I am wondering is this ? how do you save your jpeg files or tiffin that matter ? Since PS 7 does not show a reasonable DPI, do youmanually adjusting it ? .

Thanks in advance ....

I'm not sure what you are asking. Do you know that your camera captures an image of X pixels? If you print from PS you select dpi you would like to print. If you choose 300 dpi in PS the image will be smaller than if you specify 150 dpi PS. DPI is an output issue..

I recommend you print the same scene at 150, 200 250 and 300 to see if what you like from your printer. You can do this and keep the inches the same..

I use 150 dpi with inkjets and 300 with laser printers. Unless my Canon printer software uprezzes on it's own, I print @ 150 dpi. 150 is sufficient for most images..

REd..

Comment #7

&all; they want is minimum 48MB, which roughly translates to 11 x 8.5 printed page (n 300 dpi)..

But, dont be confused with dpis. It doesnt matter..

If your camera is S3, youll need to open your original file and do your usual pp first (dont sharpen). If you need to save the file during your work, always save it as psd or tiff (in case of tiff, you could set compression to lossless LZV, to keep the file size smaller). Once youre done, save the final (see above for the format), in case you wish to go back..

Now, open the Image Size. DESELECT Resample Image and set the Resolution to 72 pixels/inch..

SELECT Resample Image and type 3400 in With (top of the window). Click OK and youre done. Check the Doc in the bottom Info status filed of the image window. It should say 49.6M/49.6M. This is it. Just save the file as jpeg, compression 10 (I believe PS 7 can only save as 10  the best image quality) or 12 in case of the newer versions..

Send the file to them..

Hope this helps,Alex..

Equipment list is in the profile..

Http://www.pbase.com/alekko.

Image control:Zoom outZoom 100%Zoom inExpand AllOpen in new window..

Comment #8

Peacewarrior wrote:.

I am wondering if changing resolution from the camera default of say180 to 200 or more would degrade the picture quality for printing ? .

If so, is there a way to do this ? I am trying to fit the requirementfor Alamy of 45 megapixels from 6 megapixels camera ??? Is thatpossible ? advisable to do ? .

First, dpi is completely meaningless in the absence of a print size. If there's a dpi requirement, there must be a print size to make it meaningful. For example, 300 dpi at 8" x 10" would be 2400 x 3000 pixels or 7.2 megapixels. The image straight out of the camera is a fixed resolution, x pixels wide by y pixels high. dpi doesn't matter until it's printed..

Second, I wonder if the requirement is a 45 megabyte image rather than 45 megapixels?.

Mark..

Comment #9

Mark B. wrote:.

Second, I wonder if the requirement is a 45 megabyte image ratherthan 45 megapixels?.

It is uncompressed image size (48 Mbyte)..

Alex..

Equipment list is in the profile..

Http://www.pbase.com/alekko.

Image control:Zoom outZoom 100%Zoom inExpand AllOpen in new window..

Comment #10

Thanks very much to all and especially Alekko who gives the precise steps for me to follow..

I would have to try and do it and see if they would accept, otherwise all these thousand pictures would go to istock .

I wonder why do you change the resolution to 72 pixels per inch then resample again ???.

Thanks heaps again ... everybody .

Alekko wrote:.

&all; they want is minimum 48MB, which roughly translates to 11 x 8.5printed page (n 300 dpi)..

But, dont be confused with dpis. It doesnt matter..

If your camera is S3, youll need to open your original file and doyour usual pp first (dont sharpen). If you need to save the fileduring your work, always save it as psd or tiff (in case of tiff, youcould set compression to lossless LZV, to keep the file sizesmaller). Once youre done, save the final (see above for theformat), in case you wish to go back..

Now, open the Image Size. DESELECT Resample Image and set theResolution to 72 pixels/inch..

SELECT Resample Image and type 3400 in With (top of thewindow). Click OK and youre done. Check the Doc in the bottom Infostatus filed of the image window. It should say 49.6M/49.6M. This isit. Just save the file as jpeg, compression 10 (I believe PS 7 canonly save as 10  the best image quality) or 12 in case of the newerversions..

Send the file to them..

Hope this helps,Alex..

Equipment list is in the profile..

Http://www.pbase.com/alekko.

Image control:Zoom outZoom 100%Zoom inExpand AllOpen in new window.

Be a torch bearer ...S3 IS..

Comment #11

Peacewarrior wrote:.

I wonder why do you change the resolution to 72 pixels per inch thenresample again ???.

Theres no again ..

You wont actually change the resolution in the first step. All you do is to set it to 72 dpi, but you can leave it at any other. It really doesnt matter. All that matters is the number of pixels and thats what you need to increase..

When I purchase images from iStock or similar for my company, I get all kind of different dpis. I personally like to have 72 as default. Then I chose which dpi I need, depending if its the professional print project (set to 300 dpi and CMYK), in-house print (150-300, CMYK or sRGB) or just web (72, sRGB)..

Remind me not to use that company. I dont want to purchase up sampled images. I can do that myself, if needed. That way *I* have control over that process and quality..

Cheers,Alex...

Comment #12

Peacewarrior wrote:.

I wonder why do you change the resolution to 72 pixels per inch thenresample again ???.

No, what Alekko meant is changing the DPI without resampling. Hence, you will maintain the number of megapixels > this means the printing size will be smaller if you set to larger DPI and vice versa..

Basically the idea is like this, you have only 6 megapixels of information. You can't really get 16 megapixels of information from this 6 megapixels without estimation through interpolation. If you forcefully enlarge it by interpolation and resampling, you will see the interpolation effects which usually come out as blurry pixels..

With 6 megapixels (3000x2000), you can print 6"x4" album photos at maximum 500dpi (pretty good quality). If you would like to print at 150dpi, you can get a 20"x16.67" output, which most likely you will hang as wall photo > perfectly ok since no one will climb up and peep the pixels..

You can downsample the image for printing although. Let say you want to print 6"x4" at 300 dpi = 1800x1200 megapixels. You just need to resize your photo from 3000x2000 to 1800x1200..

The final point is that Alamy is requesting for a certain megabytes of photo which will translate directly into a certain megapixels. It doesn't matter what DPI is the photo printing. It only want to ensure the photo has some megapixels of information..

I find that the requirement set by Alamy is not very clear... They only said 48Mbytes minimum and this can translate to different megapixels..

If you are using TIFF base on 24-bit RGB, each pixels is 3 bytes > 48Mbytes means 16 megapixels..

If you are using TIFF base on 32-bit CMYK, each pixels is 4 bytes > 48Mbytes means 12 megapixels...

Comment #13

I wonder which would give the better solution ? .

Changing the DPI like to 300 or manually changing the pixel dimensions ? .

Do they matter ? .

Thanks.

Skylark_khur wrote:.

Peacewarrior wrote:.

I wonder why do you change the resolution to 72 pixels per inch thenresample again ???.

No, what Alekko meant is changing the DPI without resampling. Hence,you will maintain the number of megapixels > this means theprinting size will be smaller if you set to larger DPI and vice versa..

Basically the idea is like this, you have only 6 megapixels ofinformation. You can't really get 16 megapixels of information fromthis 6 megapixels without estimation through interpolation. If youforcefully enlarge it by interpolation and resampling, you will seethe interpolation effects which usually come out as blurry pixels..

With 6 megapixels (3000x2000), you can print 6"x4" album photos atmaximum 500dpi (pretty good quality). If you would like to print at150dpi, you can get a 20"x16.67" output, which most likely you willhang as wall photo > perfectly ok since no one will climb up andpeep the pixels..

You can downsample the image for printing although. Let say you wantto print 6"x4" at 300 dpi = 1800x1200 megapixels. You just need toresize your photo from 3000x2000 to 1800x1200..

The final point is that Alamy is requesting for a certain megabytesof photo which will translate directly into a certain megapixels. Itdoesn't matter what DPI is the photo printing. It only want toensure the photo has some megapixels of information..

I find that the requirement set by Alamy is not very clear... Theyonly said 48Mbytes minimum and this can translate to differentmegapixels..

If you are using TIFF base on 24-bit RGB, each pixels is 3 bytes >48Mbytes means 16 megapixels..

If you are using TIFF base on 32-bit CMYK, each pixels is 4 bytes> 48Mbytes means 12 megapixels..

Be a torch bearer ...S3 IS..

Comment #14

Peacewarrior wrote:.

I wonder which would give the better solution ? .

Changing the DPI like to 300 or manually changing the pixel dimensions ? .

Do they matter ? .

It doesn't matter whether you change the DPI or pixel dimensions as Photoshop will use the similar technique of resampling. But it is easier using dimensions than DPI..

For example, you would like to print 6"x4" at 300 dpi, you know exactly that you need 1800x1200 megapixels. It doesn't matter whether Photoshop read the EXIF data correctly or wrongly..

But there is one thing that you should take note when changing the dimension > you must maintain the aspect ratio..

For example, the original is 3000x2000 (3:2), and the resize is 1800x1200 (3:2) > same ratio.

Most P&S take picture at 4:3, for example 3600x2700, so when print 6"x4" (3:2), you need to crop it to 3600x2400 (3:2) first, then only resize to 1800x1200 (3:2). You lost a bit pixels from top and bottom..

For downsampling printing, as long as your printer is good, you don't really need to resize. For example, if you are asking the printer to print 6"x4" at 300dpi (1800x1200 mp) but you give a 3000x2000mp source image, the printing software will automatically resample your image to 1800x1200 for output..

For upsampling printing, it would be better to use software like Photoshop to do the interpolation instead of depending on printer software. For example, if you would like to print 12"x8" at 300 dpi (3600x2400mp), but your source image is only 3000x2000mp, you can use Photoshop to stretch the size to 3600x2400mp with some interpolation and print it...

Comment #15

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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