Do I resize, or just compress to a smaller size?

Hi guys. Unbelievably, I am still unsure of how to get the size of files down for putting on the internet, or moving jpegs around my network to different computers for family to have a copy.

I see for instance, in Pain shop pro, and also in Photoshop, I can resize say, I tiff, from like 300x 400 (whatever normal lines are for my 5D2) downward to say, 1200 by 800 or whatever, and this makes my size go down, but am I actually then changing my megapixel size of the photo, and is this a bad thing? I would like to actually have the megapixels my camera is capable on, (21). So when I change image size, is this what I am doing?

Then when I got to save my photo in Jpeg, i also notice I can chance compression (or quality in DPP) size when I am saving in to jpeg format, so what exactly is this doing, does it differ compared to image resizing, and which should I do for converting to Jpeg?> And what should I do and what format if I want to have a pic snet out to print, say over the internet to a place to have a print done? Should I send a Tiff, (Which are frickin massive), or is the Jpeg fine as long as I don't have it compressed down too much?

Thanks for the help in advance

To resize for internet use, for example this site, you need to reduce the actual pixel dimensions so that the maximum length of any side is not more than 1024 pixels, other sites have their own specific requirements. Obviously you need to keep the ratio of the dimensions the same as before or the image will look pretty odd.

When you click "save for web" you will be presented with a dialogue that apart from guiding you through the process will show you the actual MP size of the reduced image. Thats the second part of many site requirements, the images being posted must not be more than a certain number of MP.

Yes, that will reduce the storage size of the image if you save it. I tend to only save my images as TIFF files at full size because I never know what use I will make of them in future. So once I've posted an image and know its OK, I delete the jpeg.

I appreiate the answer, but you really didn't answer my question. When I post here I just link to my Fliker page, so I can post much bigger files to my fliker.

So i want to know for printing as well, how do i get my files down to manageable jpeg size, not because of what a web site requires, but what's the best way, period.

So am I to presume that I should, say, in Paint shop pro, which i use a lot, hit menu, image, resize, and resize to get my file size smaller, then use less jpeg compression when saving as jpeg, or should I NOT resize and just use the jpeg compression and compres to like 75 percent or something.

So directly
Which is preferable, using all jpeg compression to get size down, leaving my actual image size at the resolution of my camera?

Or, resizing my image while I am editing it and lowering resolution, and then having to use less jpeg compression since my files will already be much smaller already when i save as jpeg?

Thanks much

Printing, on one hand, has different requirements than web posting, emailing, sharing, etc., on the other. That is because printing needs a lot of pixels - 300 hundred of them for every inch of paper or even 360 for an Epson printer - while electronic display only needs around 100 per inch - so a 700 pixels high image will cover a large proportion of most screens.

So let's talk about prints: the easiest thing and often the best thing is to give the printer all the pixels you have and let him worry about resizing to 300 ppi. It is likely he will do a good job. However, if you are sending a lot of images for a lot of small prints, like 4x6 or 5x7, and you are on a slow upload connection, instead of leaving it to him you may want do the downsizing (and final sharpening) yourself - to 1200x1800 pixels for 4x6 inches or 1500x2100 for 5x7.

As for jpg compression, a little won't hurt and is a good space saver, but a lot of compression will cause artifacts. Every application is different, but as a rule of thumb I'd say not to go below 80% of the highest quality setting.

Resizing and compressing your files should be entirely dependant on what you want to do with them. To maintain maximum quality, you shouldn't do either. For e-mailing you may need to do one or both, depending on what the maximum file size is that your mail provider will accept. As has already been said above, for posting on the internet your image will need to meet the requirements of the web site with regard to pixel dimensions and file size. For printing, how much you can resize and maintain good quality in the print will depend on what size your final print is going to be.

From all of that hopefully you will see it is difficult to give you a definitive answer until you ask a specific question.

guitarjeff,

Hope we have shown you that a "one size fits all" approach is not going to work. I suggest you save as high a qualtity image as possible, at whatever size the camera can do, then for web use reduce as required and change to jpeg at the same time. When printing theres no need to change anything unless you have internet issues.

Lowner wrote in post #15376025
guitarjeff,

Hope we have shown you that a "one size fits all" approach is not going to work. I suggest you save as high a qualtity image as possible, at whatever size the camera can do, then for web use reduce as required and change to jpeg at the same time. When printing theres no need to change anything unless you have internet issues.

Thanks Richard. I guess I will practice what most here preach, "always save the raw files" Time to just get more hard drive space. I need to get used to saving copies for different situations. One for web, and one larger jpeg for possible prints, and the raw in case I need to do something in the future to the pic.

Only question I feel like that wasn't answered to my understanding is which offers higher quality when lowering size of image, IN A VACUUM, nothing to do with a web site or anything else, lowering size with jpg compression or resizing the image before even using jpg compression?

guitarjeff wrote in post #15377027
Thanks Richard. I guess I will practice what most here preach, "always save the raw files" Time to just get more hard drive space. I need to get used to saving copies for different situations. One for web, and one larger jpeg for possible prints, and the raw in case I need to do something in the future to the pic.

Only question I feel like that wasn't answered to my understanding is which offers higher quality when lowering size of image, IN A VACUUM, nothing to do with a web site or anything else, lowering size with jpg compression or resizing the image before even using jpg compression?

That question can't be answered in a vacuum, because which method to use will depend on what the end use is. You should resize the image when using on a web page, but you should usually* use higher compression settings (and not resize) if you're sending to a printer who won't accept files over a certain size.

When printing, use all the resolution you can, and compress as little as you can. When saving for use in social media, there's no reason to have such a large size. Context is everything, so there's no "in a vacuum" answer.

*in this context, "usually" means "always, unless your pixel count is far higher than your printer needs." That's only the case in certain circumstances, though, which you probably won't be experiencing.

It will also depend on how much you reduce an image by when resizing or how much compression you use when reducing the file size that way.

guitarjeff wrote in post #15377027
Thanks Richard. I guess I will practice what most here preach, "always save the raw files" Time to just get more hard drive space. I need to get used to saving copies for different situations. One for web, and one larger jpeg for possible prints, and the raw in case I need to do something in the future to the pic.

Only question I feel like that wasn't answered to my understanding is which offers higher quality when lowering size of image, IN A VACUUM, nothing to do with a web site or anything else, lowering size with jpg compression or resizing the image before even using jpg compression?

The point that I think you might be missing here is that you keep the RAW file, and if you need to do any pixel editing the TIFF/PSD file with all the layers etc in your archive and only produce output files when you need them, once you have used it delete it. That way your output file will always be exactly what you need FOR THAT PARTICULAR USE! As others have said there is ALWAYS going to be a context in which you are going to be using the output file, hence the produce, use, delete work flow.

For example this morning I sent four files off to a lab to have 16"×12" prints made. As they had formatting on them (a border) I generated them from the LR print module using the labs specified colour profile for the printer and with the correct number of pixels (4800×3600) and using 80% quality setting. this gave me approx 3.5Mb JPEG files which is the recommended quality/size trade off for printing. Once I get the prints back I will delete those files as I will not need them again. In fact I am only keeping them now in case there is a problem, so that I have copies of the actual files that I sent to the lab. It is the first time I have used this lab (DSCL in Manchester). If I want to make more prints at another time I will just generate the files again, it's only a couple of minutes work, and if anything has changed, such as colour profiles, that would be taken care of in the process.

Alan

At the risk of repeating anything that has already been said...

For printing:

In my experience most printers I have spoken to want 300dpi saved at jpg quality 10 (out of 12 maximum). Their position is that saving at quality 10 will significantly downsize the KB/MB size of the file - usually by over 50% - while not making any noticable reduction in quality in the print.

If you are printing at 10in x 8in then you only need an image of 3000 x 2400 - a full res 5Dmk2 image (5616 x 3744) is overkill.

For on screen viewing :

I usually share images at around 1800 px jpg 8/12 and again find that the quality reduction is negligable.

For emailing just remember that some email providers still limit the maximum size of attachments so as not to clog up their systems so emailing lots of large KB images can be problematic.

For web use :

I generally supply images at 1024px long edge at no higher than 200Kb.

BigAl007 wrote in post #15377211
It is the first time I have used this lab (DSCL in Manchester). If I want to make more prints at another time I will just generate the files again, it's only a couple of minutes work, and if anything has changed, such as colour profiles, that would be taken care of in the process.

I just want to give you some confidence in DSCL.

I have used them recently for a large mixed order with prints at 6x4, 9x6, 12x8, 18x12 and 30x20 poster and the results were fantastic. The order was fulfilled 100% in the time they said with zero errors in over 200 individual images.

How they do it at the price they charge defies belief.

I think this has been said in different ways--as I've scanned the responses, I haven't seen any incorrect advice. The best way to reduce file size is always dependent on what you intend to do with the reduced file. Reducing file size is always a matter of throwing away image detail. you can do that by compression, by reducing the size of the image, or by reducing pixel resolution.

As mentioned, moderate compression is often the best and easiest thing to do. It's extremely rare that I need to set Photoshop jpeg compression to anything higher than 10. This seems to be a logarithmic thing--going from 12 to 10 cuts the file size nearly in half with almost no difference in image quality. That depends somewhat on the amount of actual detail in the image, but I don't think twice about taking that step with all my files, whether to be printed or for the web. That's usually all that's necessary--I'll normally not resort to anything else to reduce file size for an image to be printed.

If more reduction is necessary, I'll experiment with more compression. But be careful that you're compressing your final image--not one that you intend to continue to edit and re-compress.

If you feel you can or should reduce the ppi, you need to keep an eye on your ppi requirements for the intended use. Nothing looks worse than pixellation. If you're printing, you want to keep the ppi at 300 or perhaps higher (don't know if 360 for Epson printers is a myth for practical purposes or not). If it's for the web, then you want to keep the ppi to 100 (once it was 72, but these days newer monitors are up to 100 ppi).

If you know your image will be used small, then you can cut the dimensions accordingly.

RDKirk wrote in post #15377386
...... (don't know if 360 for Epson printers is a myth for practical purposes or not).........

It's not a myth, Epsons do use 360ppi.

Lowner wrote in post #15377393
It's not a myth, Epsons do use 360ppi.

I know they use it. What may be a myth is whether it makes a difference to give them a 300 ppi or a 360 ppi file.