Pixes Per Inch / Impact on Printing

[quinn]

Relative "new guy" to Digital Photography so please go easy on me!

I have a Olympus 3020 3MP camera. The Optimal zoom is the standard 3x.

I took a large number of pictures in the "auto" mode. When I transferred the pics to my PC and viewed in Paintshop Pro they looked great. I was amazed at how much I could enlarge the pics on my PC and still see so much detail.

I started enlarging and cropping the pictures thinking that the way they showed up on my PC screen was how clear they would be when they printed. I was in for a rude awakening!

Even though I was only printing at a 4x6 size the pictures were very grainy. My assumption was that even though I had only printed to 4x6, the enlarging and subsequent cropping of the image on my PC made the image much larger than a 4x6.

I also thought the "grainy" problem might be the result of shooting at a lower quality setting. My Camera allows 4 different settings.

TIFF
HQ- JPEG
SHQ-JPEG
"X" (can't remember and don't have camera with me)

I was shooting at the SHQ level which is still a JPEG image but apparently a lower quality image then the HQ level. So this may have contributed to the problem as well

I then saw something in my Paintshop pro manual where it talked about pixels per inch and what worked well for the web vs. printing. It said 72 pixels per inch was fine for the web but printing was best a a range of 100-150.

Paintshop gives you an option to "resize" the image. One of the options is the pixes per inch. My images, as transferred from my media card, were at 72 pixels per inch. I used Paintshop to change the pixes per inch to a higher setting such as 100. This seemed to help alot with the grainy issue I was experiencing before.

However, this created huge images and in some cases caused Paintshop to crash or lock up. As a result, I figured this probably isn't the best way to adjust the pixels per inch. My next time out I tried the next higher seeting (the HQ mode). This creates 2048x1536 images. Last night I transferred them to my PC and the pixels per inch on these images is also showing as 72!

I enlarged these images little to none as I was afraid I would have a repeat of my earlier problem. I have not yet tried to print these but was wondering if I am going to still have the same issue sine the images are still 72 pixels per inch.

I am basically trying to find out the following:

1) Do images always get transferred at 72 pixels per inch regardless of the image size? If not, why would I still be getting 72 pixels per inch on the latest round of pictures I took when I used the next higest quality setting for the images (2nd only to the TIFF setting)?

2) Was the grainy issue on my first batch of images a result of the enlarging of the image (in some cases 50-60%) or using a lower image size when shooting.

While I am glad the images look good on my PC, I would like to be able to print out some of these images with worrying about the grainy issue.

3) How much can someone safely enlarge their images using image editing software?


Sorry about the length of this message. I was trying to be as detailed as possible

Thanks

[Newbie]

The first time, were you shooting in SHQ mode or in the 2nd least compressed JPEG mode ? Because SHQ more is less compressed than HQ mode, so it makes SHQ a better choice.

As for your question, it is a bit hard to answer since I do not know anything about how much u cropped and all, but the reason why your print did not looked as good as u wanted was probably because u cropped it too much or because you saved the image after a modification was made to it too many times. Because JPEG images are compressed images, each time you make a modification and save the image, the image is compressed again. Your SHQ image should be somewhere around 1.5mb size, check how big your file was before you printed it(if you still have it). Also, something which could have affected your shot is if you have used digital zoom and then cropped your shot.

Make sure you turn off digital zoom then take some pictures at SHQ, if you find one you would like to print, do it, you will see the image quality should be picture quality provided that you print 4x6 or 5x7... You can also probably crop the image 100%(I think this means removing half of it) and u should get some excellent result, tho a bit below picture quality... When viewed from 1' it should look like picture quality.

TIFF is good, but if you need to fit more photos, shoot in SHQ all the time, you can use digital zoom, but if you do keep in mind that it acts the same way as cropping does.

For my part, I do not own your camera, never even seen it to be honnest. But I know that 3mp cameras are able to print picture quality up to 5x7 and that their 8x10s will look excellent.

I own a 5mp camera and wanted to see how bad digital zoom was, also I wanted to see how bad a picture printed with less ppi would look like. So I used my digital zoom to the maximum which produced an image the equivalent of a 640x480 picture, the result was far from being as terrible as people mentionned and when printing, I admit it was possible to see pixelization when 6 inches from the picture at 2' it looks good. This was printed in 4x6 size.

[John_Reed]

Relative "new guy" to Digital Photography so please go easy on me!

I have a Olympus 3020 3MP camera. The Optimal zoom is the standard 3x.

I took a large number of pictures in the "auto" mode. When I transferred the pics to my PC and viewed in Paintshop Pro they looked great. I was amazed at how much I could enlarge the pics on my PC and still see so much detail.

I started enlarging and cropping the pictures thinking that the way they showed up on my PC screen was how clear they would be when they printed. I was in for a rude awakening!

Even though I was only printing at a 4x6 size the pictures were very grainy. My assumption was that even though I had only printed to 4x6, the enlarging and subsequent cropping of the image on my PC made the image much larger than a 4x6.

I also thought the "grainy" problem might be the result of shooting at a lower quality setting. My Camera allows 4 different settings.

TIFF
HQ- JPEG
SHQ-JPEG
"X" (can't remember and don't have camera with me)

I was shooting at the SHQ level which is still a JPEG image but apparently a lower quality image then the HQ level. So this may have contributed to the problem as well

I then saw something in my Paintshop pro manual where it talked about pixels per inch and what worked well for the web vs. printing. It said 72 pixels per inch was fine for the web but printing was best a a range of 100-150.

Paintshop gives you an option to "resize" the image. One of the options is the pixes per inch. My images, as transferred from my media card, were at 72 pixels per inch. I used Paintshop to change the pixes per inch to a higher setting such as 100. This seemed to help alot with the grainy issue I was experiencing before.

However, this created huge images and in some cases caused Paintshop to crash or lock up. As a result, I figured this probably isn't the best way to adjust the pixels per inch. My next time out I tried the next higher seeting (the HQ mode). This creates 2048x1536 images. Last night I transferred them to my PC and the pixels per inch on these images is also showing as 72!

I enlarged these images little to none as I was afraid I would have a repeat of my earlier problem. I have not yet tried to print these but was wondering if I am going to still have the same issue sine the images are still 72 pixels per inch.

I am basically trying to find out the following:

1) Do images always get transferred at 72 pixels per inch regardless of the image size? If not, why would I still be getting 72 pixels per inch on the latest round of pictures I took when I used the next higest quality setting for the images (2nd only to the TIFF setting)?

2) Was the grainy issue on my first batch of images a result of the enlarging of the image (in some cases 50-60%) or using a lower image size when shooting.

While I am glad the images look good on my PC, I would like to be able to print out some of these images with worrying about the grainy issue.

3) How much can someone safely enlarge their images using image editing software?


Sorry about the length of this message. I was trying to be as detailed as possible

Thanks

Your camera captures an image of, say, 2048 X 1536 pixels, and stores it as a compressed JPEG file onto your memory card, whatever that is. Now, when you download it, your computer software makes an arbitrary choice of how to display the image after decompression. A lot of programs select 72 dpi or pixels/inch, as that's the old norm for display resolution. So, if you download a 2048 X 1536 image, if you look at the dimensions on your screen, it'll show up as an image 28.44 inches wide, by 21.33 inches. That has nothing to do with print size. When you go to print, the number of image pixels determines how large you can print without "graininess." Usually, anything more than 150 pixels/inch will result in a smooth, sharp looking print. So for your images, that means you could print something 13.65 inches X 10.24 inches and get a good-looking print. Other more conservative types say you should go for 300 pixels/inch, which would take you down to 7X5 if you were to comply with that stricter requirement. Either way, you've got plenty of pixels for a 4X6 print, and you don't need to add pixels to do the trick. Generally, if you choose the print size in your editing program, the computer will make the calculation to give you exactly the distribution of pixels you need to create the size print you want. And don't confuse image pixels with "Printer dpi," either, since most printers print at 1400+ dpi. Those "dots" are what the printer squirts onto the paper as it proceeds through the print. For example, if you print at 150 pixels/inch with a printer printing at 1500 dots/inch, the printer will "fill" every pixel's space with about 10 of its own dots.

[quinn]

Newbie,

Thanks for your response to my message.

First off, you are correct that the 2nd time time I was shooting in the SHQ mode rather than HQ. (I got those mixed up in my first message)

The images I printed and had such bad results were the ones I shot in the HQ mode, which is more compressed. The strange thing is that the manual that comes with the camera indicates that the resolution (2048x1536) is the same for SHQ or HQ. However, it does indicate that SHQ is "low compression" vs. HQ which is "normal" compression.

I did do some extensive cropping on the inital pictures I took in order to better zoom in on the images that I took. I also went back and re-edited pictures a couple different times. So its possible that the 2 items you mentioned (extensive cropping and saving the images multiple times) impacted on the printing.

I went back and checked the size of some of the intial images I printed (after cropping and editing). These images were taken in the HQ mode and the size of the images were as low as 183KB in some cases and 650k in others.

I was a bit confused where you said I should be take to probably crop the image 100% and still get excellent results with a 4x6 picture (even if a bit below picture quality). Would you only consider extensive cropping beyond 100% ?

I haven't yet tried to print out the images I took in the SHQ mode. I got nervous when these were showing up on my computer with a pixels count of 72. However, based on what John Reed explained in his message below it doesn't appear this has nothing to do with print size but is simply the display resolution on my PC.

I am going to try and print out the SHQ images tomorrow. I avoid cropping these anymore than 30-50% so I am anxious to see how they come out.

Thanks again for your input.

Quinn

[quinn]

John--

Thanks very much for responding to my questions. Your response was very helpful, particularly as to why I was continuing to see 72 Ddi / pixels per inch when I uploaded images on my PC that were shot in different compression modes.

You indicated that its the number of "image pixels" that determine how large I cant print without "graininess". The image pixes is based on the image pixels of the camera I am using, correct? Therefore with a 3.2 MP camera I should have plenty of image pixels to print out an excellent 4x6 photo.

Based on the fact that this didn't occur I am assuming this is because of the image itself being too compressed based on the extensive cropping/zooming in of the image. This resulted in me printing images where the file size was between 183k and 680k. Therefore, even though a 3.2 MP camera should have plenty of image pixels to print out a 4x6 image, this didn't occur because of the higher JPEG compression level I used AND the extensive cropping. Is this correct?

What is your opinion as to the percentage of the image that can be cropped or zoomed in on before impacting the quality?

I suppose even though I specified I wanted to print a 4x6 picture, the compression was too great to ensure the necessary pixels were available to print a high quality image?

[jaykinghorn]

Your manual is correct in stating that both SHQ and HQ have the same number of pixels what differs is how much they are compressed. JPEGs try to make the file size small by averaging areas of continuous tone.

A standard rule of thumb is to create an imageat finished print size at 300ppi. You certainly can deviate from this rule, but it is a good starting point. To calculate how many pixels you need for a high quality print, simply multiply the print dimensions by the image resolution. For a 4x6 print you need 1200x1800 pixels. (4x300=1200;6x300=1800).

I hope this is helpful.

Jay Kinghorn
RGB Imaging

[quinn]

Jay--

Thanks for your response (and the formula!)

It sounds like based on your message that a high quality 4x6 photo should be sized at 1200 x 1600 (on average).

The size of my original file was 2048x1536.

1) Using this scale the measurement of my file is already below the standard (1536 vs. 1600) without ANY cropping at only a 4x6 size. Is the first number (2048) the more important indicator for printing and therefore I shouldn't be concerned that 1536 is below the 1600.

2) Assuming I am printing a 4x6 photo, does this mean I can crop the photo nearly 50% to 1200 (vs. the original size of 2048) and still achieve a high quality print? Of course this woulid continue to bring the second measurement (1536) down as well so I am not sure if this is correct.

3) It sounds like my problem isn't so much the size of my original files, particularly if they are 2048 x 1536, but rather the impact of the further editing I am doing with my Digital Imaging software (Paintshop Pro). Again, this is mostly zooming in /cropping of the original images. There is an option in Paintshop Prop that you can "view image size" or something like that. This brings up the dimensions of the photo.

Do you know if this is the dimensions of the actual file after any editing has occurred or simply the dimensions of the file as it is displayed on my computer screen (similar to how it it is showing 72 Pixels per inch but this refers to the image on the computer screen vs. the actual pixels of the image for printing purposes)

Bottom line, I am trying to determine if AFTER I have edited the photo further (resulting in further compression) if there is a way I can view the "new" size of the image for printing purposes.

I went back to some of my original images that were cropped and zoomed in extensively. Some of them are in "my pictures" on my PC. When I click on properties all I can see is the file size. For example, 431k. I am not sure how this would equate to the formular you provided earlier.

Thanks for your help!

[jaykinghorn]

Jay--

Thanks for your response (and the formula!)

It sounds like based on your message that a high quality 4x6 photo should be sized at 1200 x 1600 (on average).

The size of my original file was 2048x1536.

1) Using this scale the measurement of my file is already below the standard (1536 vs. 1600) without ANY cropping at only a 4x6 size. Is the first number (2048) the more important indicator for printing and therefore I shouldn't be concerned that 1536 is below the 1600.

The longest dimension needs to be 1800. You have plenty of pixels for a 4x6 and enough for a very good 5x7.

2) Assuming I am printing a 4x6 photo, does this mean I can crop the photo nearly 50% to 1200 (vs. the original size of 2048) and still achieve a high quality print? Of course this woulid continue to bring the second measurement (1536) down as well so I am not sure if this is correct.

The quality would still be acceptable. Much better though, to get closer to your subject, effectively cropping in camera.

3) It sounds like my problem isn't so much the size of my original files, particularly if they are 2048 x 1536, but rather the impact of the further editing I am doing with my Digital Imaging software (Paintshop Pro). Again, this is mostly zooming in /cropping of the original images. There is an option in Paintshop Prop that you can "view image size" or something like that. This brings up the dimensions of the photo.

I haven't worked in Paintshop Pro, so I really couldn't answer that question. Perhaps someone else from the list could.

Do you know if this is the dimensions of the actual file after any editing has occurred or simply the dimensions of the file as it is displayed on my computer screen (similar to how it it is showing 72 Pixels per inch but this refers to the image on the computer screen vs. the actual pixels of the image for printing purposes)

Bottom line, I am trying to determine if AFTER I have edited the photo further (resulting in further compression) if there is a way I can view the "new" size of the image for printing purposes.

I went back to some of my original images that were cropped and zoomed in extensively. Some of them are in "my pictures" on my PC. When I click on properties all I can see is the file size. For example, 431k. I am not sure how this would equate to the formular you provided earlier.

You basically have three elements at work. 1) The image size which is the number of pixels your image contains.(2048x1536) 2) The size of the file on your hard drive (431K). This doesn't tell you that much about the file unless you want to email it to a friend and are trying to keep the attachment size below 500K. 3) The JPEG compression, which is the amount of averaging your camera, or editing software, is doing to your image to make the file size small. Your best bet is to choose the JPEG option that gives you the least amount of compression (JPEG with the fewest number of images on your card). This will give you the best quality.

Thanks for your help!

You're welcome. I'm glad I could help.

Jay Kinghorn
RGB Imaging

[quinn]

Hello Jay,

Thanks once again for your feedback. However, there is 1 part of your response that I didn't quite understand.

I mentioned that according to your formula a high quality 4x6 photo should be sized at 1200 x 1600 but that the size of my original file was 2048 x 1536. I asked if this was a problem since the 2nd dimension (1536) was already below the 1600 threshold and I had not yet done any editing or cropping.

You replied that the "longest dimension" needs to be 1800 and therefore I had plenty of pixels for a 4x6 or 5x7.

I am not sure on what your referencing as being the "longest" dimension. Is this the first number (2048) or the second number (1536). I am assuming it is the first number since this is well over the 1800.

I am just a bit confused since according to your formula the dimensions for a 4x6 were ideally 1200 x 1600. Where did you come up with the 1800?

[jaykinghorn]

The longest dimension for a 4x6 print needs to be 1800 pixels long, not 1600. (300ppix6inches=1800 pixels) Your camera shoots 2048x1536. As long as the longest dimension (this depends whether the image is in portrait or landscape orientation) has more than 1800 pixels and the shorter dimension has more than 1200 pixels you'll be in good shape. Your file qualifies on both counts with a little room to spare. For a 5x7, you need 2100 pixels on the long dimension (300ppix7inches=2100 pixels). You're just shy of the 300ppi guideline, but the difference won't be noticable in a finished print. On the shorter dimension (300ppix5inches=1500pixels) you have a few pixels left over.

So, you should have no problem printing your images at 4x6 and 5x7.

Does that description help clarify things for you?

Jay