EOS Canon Rebel SL1 resolution of RAW+JPEG images

[Riki]

Dear readers,
I have an EOS Canon Rebel SL1. I shoot in RAW+JPEG (highest quality. However the resolution is only 240dpi. I need it to be 300 for good print quality. How could I do this? The manual wasn't helpful in this regard and the Canon forum only answers e-mails for US citizens. I would appreciate an answer.
Thank you,
Riki

 

[Ysarex]

Dear readers,
I have an EOS Canon Rebel SL1. I shoot in RAW+JPEG (highest quality. However the resolution is only 240dpi.

No, it is not.

I need it to be 300 for good print quality.

No, you do not.

How could I do this?

You can change the PPI value assigned to your files with the software you use for processing.

The manual wasn't helpful in this regard and the Canon forum only answers e-mails for US citizens. I would appreciate an answer.
Thank you,
Riki

The resolution of your camera is 5184 X 3456 pixels. JPEGs saved by your camera have a PPI value set by the camera processing software of 72 PPI. The raw (CR2) files saved by your camera have no assigned PPI value. The 240 figure you're finding is coming from some software application.

The files saved by your camera and your photo files in general do not have a DPI value. DPI is (D)ots (P)er (I)nch and applies to printing. The "D" in DPI is a dot of ink on paper. There is no ink in your computer files. Your photos may or may not have an assigned PPI value. PPI is (P)ixels (P)er (I)nch and it is NOT a measure of the resolution of a camera and/or image file. PPI is the resolution of you image over a specific size. Without the size specified the PPI value is meaningless.

So you're looking at your photo in some software application and seeing a PPI value of 240. That begs the question 240 PPI over what size? Here's Photoshop's Image size dialog:

That's the same image (both dialogs) from a Canon SL1 and note the resolution is 5184 X 3456. In the left side dialog the PPI resolution is 72 as assigned by Canon when the file was saved in the camera. Note the 72 X 48 inches document size. In the right side dialog the PPI value is 1000. Note the real resolution of the file remains unchanged and the document size is now 5.184 X 3.456 inches.

NOTE: The industry has hopelessly confused the two values DPI and PPI and we have no reason to expect it will ever get straightened out or clear in the minds of most users.
NOTE: The 300 DPI figure which in fact should be 300 PPI which would in fact require a printer DPI value of 2400 is old and no longer appropriate. We've changed the technology such that lower image PPI values now produce equivalent photo quality output to the old 300 PPI value we used to use for offset printing with film generated line screens. As such a value of 240 PPI is quite adequate for good print quality.

I posted the same photo side by side. The one on the left is 300 PPI while the one on the right is 5000 PPI. Does the one on the right have higher resolution than the one on the left?

Joe

 

[Riki]

Dear readers,
I have an EOS Canon Rebel SL1. I shoot in RAW+JPEG (highest quality. However the resolution is only 240dpi.

No, it is not.

I need it to be 300 for good print quality.

No, you do not.

How could I do this?

You can change the PPI value assigned to your files with the software you use for processing.

The manual wasn't helpful in this regard and the Canon forum only answers e-mails for US citizens. I would appreciate an answer.
Thank you,
Riki

The resolution of your camera is 5184 X 3456 pixels. JPEGs saved by your camera have a PPI value set by the camera processing software of 72 PPI. The raw (CR2) files saved by your camera have no assigned PPI value. The 240 figure you're finding is coming from some software application.

The files saved by your camera and your photo files in general do not have a DPI value. DPI is (D)ots (P)er (I)nch and applies to printing. The "D" in DPI is a dot of ink on paper. There is no ink in your computer files. Your photos may or may not have an assigned PPI value. PPI is (P)ixels (P)er (I)nch and it is NOT a measure of the resolution of a camera and/or image file. PPI is the resolution of you image over a specific size. Without the size specified the PPI value is meaningless.

So you're looking at your photo in some software application and seeing a PPI value of 240. That begs the question 240 PPI over what size? Here's Photoshop's Image size dialog:

View attachment 141776

That's the same image (both dialogs) from a Canon SL1 and note the resolution is 5184 X 3456. In the left side dialog the PPI resolution is 72 as assigned by Canon when the file was saved in the camera. Note the 72 X 48 inches document size. In the right side dialog the PPI value is 1000. Note the real resolution of the file remains unchanged and the document size is now 5.184 X 3.456 inches.

NOTE: The industry has hopelessly confused the two values DPI and PPI and we have no reason to expect it will ever get straightened out or clear in the minds of most users.
NOTE: The 300 DPI figure which in fact should be 300 PPI which would in fact require a printer DPI value of 2400 is old and no longer appropriate. We've changed the technology such that lower image PPI values now produce equivalent photo quality output to the old 300 PPI value we used to use for offset printing with film generated line screens. As such a value of 240 PPI is quite adequate for good print quality.

View attachment 141782 View attachment 141783

I posted the same photo side by side. The one on the left is 300 PPI while the one on the right is 5000 PPI. Does the one on the right have higher resolution than the one on the left?

Joe

 

[Riki]

Dear Joe,
Thank you very much for taking the time to reply to me. I really appreciate your help.

Here's how the whole DPI/PPI issue came up.

I process my photos in Photoshop and save them as PSDs. They are usually really large files. If I want to send them to Shutterstock, they have to be in JPEGs, and have to have a minimum size of 4MB.

When I convert my PSD files to JPEGs, some of them are less than 4MB.

So those images simply cannot be sent.

Does the 240 PPI resolution shown in Photoshop have anything to do with my JPEG size being less than 4MB?

Is there anything I can do to make my compressed files larger than 4MB? Such as having a heavier PSD file to start with?

And just out of curiousity, if I were to print out a 4MB file, how large would that image be?

Thanks again for your help,

Riki

 

[Ysarex]

Dear Joe,
Thank you very much for taking the time to reply to me. I really appreciate your help.

Here's how the whole DPI/PPI issue came up.

I process my photos in Photoshop and save them as PSDs.

Are you processing the CR2 files in Photoshop?

They are usually really large files. If I want to send them to Shutterstock, they have to be in JPEGs, and have to have a minimum size of 4MB.

When I convert my PSD files to JPEGs, some of them are less than 4MB.

Two factors only matter here: 1. The pixel X pixel resolution of the file and 2. The JPEG quality setting.

So those images simply cannot be sent.

Does the 240 PPI resolution shown in Photoshop have anything to do with my JPEG size being less than 4MB?

No. See comment directly above.

Is there anything I can do to make my compressed files larger than 4MB? Such as having a heavier PSD file to start with?

See comment directly above.

And just out of curiousity, if I were to print out a 4MB file, how large would that image be?

However big you printed it. You could print a 4MB file at 2 x 3 inches and at 2 x 3 feet and at 2 x 3 yards, etc. The imge size in MB does not determine print size.

Joe

Thanks again for your help,

Riki

 

[Riki]

Thanks.

I convert my CR2 files to DNG and process them in Photoshop.

When I start out, my file sizes are 5184x3456 pixels. I rarely crop because I usually get it right in camera. Some composites get a lot larger than that.

The JPEG setting I use is the largest possible one and the quality is also the highest.

Maybe I did not understand the nature of JPEG compression.

How much smaller does a PSD file get when it is converted into a JPEG?

Is there some kind of ratio which I can use to calculate how much smaller a PSD file will get if it is converted to JPEG?

If I could figure that out, it would save me a lot of trouble and I could simply find another use for the smaller files.

Thanks again,

Riki

 

[Ysarex]

Thanks.

I convert my CR2 files to DNG and process them in Photoshop.

Why convert to DNG?

When I start out, my file sizes are 5184x3456 pixels. I rarely crop because I usually get it right in camera. Some composites get a lot larger than that.

The JPEG setting I use is the largest possible one and the quality is also the highest.

So file size as an 8 bit PSD would be roughly 5184 X 3456 X 3 = 51.2 megabytes. If you save a PSD or TIFF file it will be in that range.

Maybe I did not understand the nature of JPEG compression.

How much smaller does a PSD file get when it is converted into a JPEG?

JPEG compression is content dependent. If the data is dense the compression rate is less. So for example a forest scene without sky would compress less than a landscape with an expanse of blue sky. At the highest quality setting Photoshop will compress the above 51.2 megabyte file by nearly 70% 51.2 X .3 = 15.3 megabytes with dense data. If the photo is a landscape with a blue sky and say some ocean the same JPEG compression may reach 80% 51.2 X .2 = 10.2 megabytes. Even 10.2 megabytes isn't close to 4 megabytes. So you're either cropping a lot more than you think, using a lower JPEG compression rate or something else is going on.

Joe

Is there some kind of ratio which I can use to calculate how much smaller a PSD file will get if it is converted to JPEG?

If I could figure that out, it would save me a lot of trouble and I could simply find another use for the smaller files.

Thanks again,

Riki

 

[Riki]

Thanks Joe.
I convert to DNG because a tutorial I used to help me get to work in with RAW files suggested doing that if their method of working with RAW did not work. I had some problems downloading the software.
The Adobe DNG converter works for me.
Thank you for breaking down my question and answering it clearly. Now I understand the math behind the sizes and also the nature of JPEG compression. The files I converted had images of flowers on a black background. The ones that were the smaller that 4MB had the least details. They had used filters to make them painterly, which eliminated quite a lot of the detail.
I will be posting question about monitor calibration on another thread shortly.
Once again, I appreciate your help.