What is the best file size when photographing?

[soupman]

I am using a Canon EOS Digital Rebel xT. If I am not going to enlarge a photo to poster size, should I use a smaller file size in my camera?

For instance, currently I have my camera set for "L" which is 3456 X 2304. This seems to translate to 32"X48" (according to the CS3 Bridge metafile). That sounds huge.

So, if I am only printing 8"X10" photographs, is it better to use "M" 2496 X 1664, or "S" 1728 X 1152?

The reason I ask is when I try to resize the large file to say 4"X6", the photo is distorted and the quality deteriorates.

(I'll ask about RAW later when I learn a little about CS3.)

Thanks

[RSStory]

The trick is that the print size you are talking about is at 72PPI. Here are 2 screen caps and all I did was change the PPI from 72 to 300.

[PhotosbyChuck]

In general, the larger you want to print the more pixels you want in the original.

Print Sizing
Common practice is to plan for a 300DPI print, but prints down to 150DPS are very good and lower is possible, depending on the detail in the photo.

A common guideline is:

Minimum Resolutions by Print Size

 4"x 6" = 1024 x 768 pixels 
 5"x 7" = 1280 x 960 pixels 
 8"x10" = 1600 x 1200 pixels 
10"x15" = 2048 x 1536

Please note the word minimum. More pixels is better and some photographs will not be acceptable at the minimum.

By the way, the DPI you set in PhotoShop or other software does not affect the size of the file in any way.

You should not see distortion if your ratios match the print ratio. Your sensor is 2x3 in terms of its ratio. (The longer side is 1.5 times as long as the shorter side). That's the same as a 4"x6" print. So, if you print 4x6, you'll not see distortion. (You could till see color shifts or quality loss, but that's not due to the resolution, but other factors).

If you are printing to a size that does not match your ratio, such as 8x10, you need to crop your image to the same ratio for best results. If you do not, the software will either:

1) Stretch one dimension to make the photo fit. This is the worst choice as it will distort one axis.

2) Arbitrarily crop some portion of the image to make it fit. Not so great either since it may crop important elements.

3) Leave a border on one or both sides. The best option in terms of quality, but not so great if you were planning on framing the photo. A white border may show thru the frame on 2 sides.

Screen Resolutions

Screens were about 72dpi many years ago. People still use this number and you'll see it all over the Internet, but it's rarely true these days. Take your own monitor measurement. How wide is your monitor in inches? What is the horizontal resolution? Divide the two.

My monitor is 20.25" wide at 1920 pixels. That's a resolution of ~95DPI.

(Remember to use the width, not the diagonal measure! My monitor is 24" diagonal, but that means nothing to DPI...it just lets the manufacturer use the largest possible measure to make it sound big!)

In general, with planning for the web, 72DPI is pretty good, but may not look the best on high res monitors. Trouble is, you don't know what your viewers will have and even if you did, you're stuck showing the all the same image anyway. So, most people still use 72DPI for web publishing.

I probably just rambled more than you wanted -- so let me summarize by saying that if you want to print 4x6 your "S" setting is fine. But do keep in mind that using that setting will limit your ability to crop it and still maintain acceptable print quality.

[r_fredrick_smith]

Originally Posted by soupman

I am using a Canon EOS Digital Rebel xT. If I am not going to enlarge a photo to poster size, should I use a smaller file size in my camera?

For instance, currently I have my camera set for "L" which is 3456 X 2304. This seems to translate to 32"X48" (according to the CS3 Bridge metafile). That sounds huge.

So, if I am only printing 8"X10" photographs, is it better to use "M" 2496 X 1664, or "S" 1728 X 1152?

The reason I ask is when I try to resize the large file to say 4"X6", the photo is distorted and the quality deteriorates.

(I'll ask about RAW later when I learn a little about CS3.)

Okay, you're getting answers, but I'm not sure they address the core question. to the first part - what size should you shoot in camera? You should always shoot at the largest size. Why? Well if you later decide you need more from the image (larger size, more post processing, etc), then you'll have the most the camera can deliver. If you shoot at a smaller resolution in camera, then you've already thrown away some of the data. That is one of the advantages of RAW, that you save ALL the data and then can make important decisions later when you are working with the image.

Second, there is no reason a file of ANY resolution should deteriorate as you shrink it to 4x6 unless you're doing something wrong in your Photo Editor.

If you use the Image Size tool in PS, there are any number of ways you can go wrong. You have to be sure that constrain proportions is checked for example or you'll mess up the photo. When reducing you have to choose the right resampling choice, etc. I never bother with this tool, because I use a different work flow. I use a little thing called WP Pro to reduce the size of my images for their target. I then use Save for Web to save them out. If you want to do it all in Photoshop, you can just use Save for Web and reduce the size there. Save for web also gets rid of all the clutter to reduce the file size to the smallest size it can for bandwidth issues.

Generally the DPI is okay right out of the camera (when saved at maximum size), so you would just leave it alone if printing. WP Pro leaves the DPI alone.

But the bottom line is to always shoot at the highest resolution the camera will allow.

Cheers,
rfs

[RSStory]

Great point from RFS. Why would you want to limit what you can do later. I know some people will shoot RAW + small jpg. They can then use the jpg, or if they need to doa larger print they can fall back on the RAW

[r_fredrick_smith]

Originally Posted by RSStory

Great point from RFS. Why would you want to limit what you can do later. I know some people will shoot RAW + small jpg. They can then use the jpg, or if they need to doa larger print they can fall back on the RAW

And they can even skip the "+ small jpg" if they want, since there is a small jpg (about 1500x1000) embedded in the RAW image file. Programs like BreezeBrowser can work directly with that image (I use them for quickie previews for people on a laptop).

Cheers,
rfs

[PhotosbyChuck]

Sometimes saying it differently is best, eh.

But if you mention RAW, you might have to mention sRAW...but the conclusion is the same. Shooting at the highest resolution is best as it will leave you with the most options later.

[r_fredrick_smith]

sRAW is about 40% smaller in filesize than RAW. But what do you give up in that 40% file reduction? I still don't know and as a result would not want to shoot sRAW. I always amazes me how vague the manufacturers can be on things like this. The bottom line is I want all the data for future use. How do I know now what my future use will be? Well I don't. I often have a guess -- but things can change. So I want the most data I can get so I can react to the changes. Since sRAW is still (in my mind) and unknown, I would never use it.
Cheers,
rfs

[soupman]

A lot of great information! I just purchased CS3 last weekend and now I am learning how to use it (on my own with a book and DVD).

I tried the Image Size and pretty much did what RSStory suggested (except it was defaulted to 72 dpi). The photo was originally 32" X 48". I resized it to 4" X 6" and the resulting photo was pixilated. After RSStory's note, I went back and resized it...except this time I went into Auto Resolution and set it for Best. It was defaulted to 133 lines/inch. When I executed this, the photo looks great.

I guess I will practice with it more. I was concerned that a larger file being shrunk to such a small file in comparison would cause pixilation, etc. (But intuitively it did not make sense that would be true. I felt that the more pixils the better.)

I really appreciate everyones' help!

Thanks

[PhotosbyChuck]

Ah, that makes sense as to why you're getting distortion. Let me explain a bit further...

An image has a pixel resolution, nothing more. If you have an image that is 3000 x 2000, that's exactly what it is. DPI is just a way to figure out how large such an image would be in a given medium. If you print this image at 300DPI, you'll get an image that's 10" x 6.67". If you view it on a 100DPI screen, it will be 30" x 20" (probably too large to see on any screen!

So, if PS is telling you that an image is a given size, it's just doing that same math for you. At 72DPI, your "L" setting image would indeed be huge. If you resize that image to 4" x 6" at 72 DPI, it will display exactly that large on a screen that's 72DPI. If however you print it (at 300DPI), it will be not much bigger than a postage stamp.

There's your problem. You're not printing a postage stamp -- you're trying to print a 4x6. But there's not enough information in the resized version to print a 4x6 at 300DPI, so the printer software blows the image back up and you see a tremendous loss of detail.

If you resize for prints, keep a 300DPI setting so you have good detail. If you resize for the screen, 72DPI is fine.