Sending photo's by e-mail

COVKID

When sending photo's and you reduce the pixel size,does this reduce the quality received.If the person at the other end intends to print,is it best to send the original size. I know it takes longer, is it better? Is there any way of increasing the small size back to the original once you have received it.
Thanks

isofa

Once you resize a bitmap image down, you cannot upscale it back without loosing detail.

Say you have a 3000 x 2000 pixel image from a digital camera, (the resolution it is set to is irrelevant, it could be 72dpi, 200dpi, 300dpi, doesn't matter because it is still 3000 x 2000 pixels.)

If you resize this image down to say 1000 x 667 pixels, the image is now 2/3s smaller than it was before.

If you send this to someone and then they upsize it back to 3000 x 2000 it will be heavily pixelated because effectively the software is tripling the pixels in the smaller image.

darich

isofa wrote: »

If you resize this image down to say 1000 x 667 pixels, the image is now 2/3s smaller than it was before.

It's way smaller than only 1/3 the original size.
3000x2000 = 6mp.
1000x667 = 0.67mp.
it's about 1/10 the original image - I realize it's only an example but the new size of the image is really only suitable for a webpage or viewing on a monitor since decent images will be printed at around 300dpi.
EDIT:
Use jpegs to send via email - they're smaller but still retain good quality.
Using photoshop is good for reducing image size but microsoft paint does an ok job although not as good as photoshop - ms paint is free with windows - photoshop costs hundreds of pounds.
As isofa says - once an image is reduced it cannot be enlarged back to the original size without significant quality loss.

espresso

Irfanview will easily re-size your images either by pixels, in inches or in cm. If you have 8 or 10 mega pixel images although some quality would be lost, you could re-size them down to say 3 or 4 mega pixel and they should still produce acceptable prints.

isofa

A large JPEG will still produce a large file, say off a pro DSLR with 10-12 Megapixels, but it all depends on the quality and level you are working at, and how many you are sending via email, how quick your connection is etc. I personally never use JPEGs until the last stage as they loose too much quality, (I shoot in RAW normally, and work in TIFF).

If you really know what you are doing, and want the ultimate in efficient file sizes, find out what size the recipient wants to print the image, and assume for sake of argument the output resolution will be 300dpi.

Say they want to print the picture at 6 x 4 inches which is roughly 150 x 100 mm. At 300 dpi this would be exactly 1772 x 1181 pixels

So therefore resize your image to this size. If you image ratio makes it larger in one dimension than the other, resize it uniformly in the smallest dimension and crop off the excess section, never resize without constraining proportions, otherwise you'll distort the image.

Also always keep your original high-res file in case you want to do something else with it later!

Use Photoshop if you are a professional, or have the money, Photoshop elements if you are on a budget (look for the Image Size command), Irfanview is an excellent free recommendation, as is the GIMP.

COVKID

Thank you both. I realize now i am getting confused between pixels and d.p.i.
The more dpi the better the picture i presume and this is governed by the camera. I use Picasa which appears to be jpeg.I can see it appears to be more complicated than i thought and i need to get a good book.On Picasa my pictures are 2048x1536, when e/mailed 480pixels.Do i need to send them at the original size to get the best print 6x4 or does'nt it matter .
Thanks

isofa

Your 2048x1536 image would print at nearly 5x7" (actually it'd be 17.34 x 13cm) at 300dpi and if you were printing this on a good inkjet or at a high-street shop such as Jessops, it'd be excellent quality.

Pixels make up the image, a 2048x1536 pixel image will always have 2048x1536 pixels in it regardless of whether it is set to print at: 72dpi, 150dpi, 300dpi, 1200dpi, etc (unless you deliberated resize it, technically known as "resampling"). However as the resolution increases, the output size decreases.

Increasing the dpi (i.e. the resolution), but retaining the same amount pixels in the image will make it print smaller, but at a higher resolution. So in the example above, if you were to print it at 400dpi rather than 300dpi it print at 13 x 9.75cm.

This is quite a large topic, but in essence, dpi (dots per inch) in this case determines the output size based on the pixels.

COVKID

Thank you all again especially isofa,you have answered my question.I need to send some special photo's to my son in Australia and he will get them printed at a photography shop.I will send them at the large size so he can get some good 5x7 photo's.As i said before,quite an involved but interesting subject.

darich

isofa wrote: »

Say they want to print the picture at 6 x 4 inches which is roughly 150 x 100 mm. At 300 dpi this would be exactly 1772 x 1181 pixels

If the image is to be 6 x 4 inches at 300dpi (dots per inch) then millimetres are not relevant or required.
The size is 1800 x 1200 - admittedly there would be no discernable difference in quality but it's worth pointing out how the numbers are calculated.


It's also worth remembering that larger images eg 18x12, 24x16 or anything around that size and larger will be viewed from further away. In those cases the dpi can be reduced to 240 or even 200 for the larger sizes eg 30x20.

Zahc

As far as resizing is concerned, I'm a big fan of this stand alone, free, program;

http://bluefive.pair.com/pixresizer.htm


Zahc

COVKID

Thank you darich and Zahc, i will look into your comments.