DPI etc

[Russethouse]

 I've always believed that the dpi for any photo intended for print (magazine) should be 300 minimum however using Irfanview the dpi given in 'Re size/Re sample' of quite a few pics is 72 with brackets that say (auto calc for cm/inches)

However if I use http://tiporama.com/tools/pixels_inches.html and fill in the Image width, Image height in Pixels and change resolution of the output device to  300 I get a measurement which leads me to believe that the image will reproduce Ok up to a size of 2.85 x 4 inches

Am I missing something ? I can be extremely stupid about this sort of thing...... [8-)] [8-)]

[Théière]

From memory websites only use 72dpi so if they are larger it just produces slower loading times. On my website I not only used 72dpi but also reduced the quality setting to 80% which made the pics load much faster without any real discernible reduction in quality.

Chez Nous for example need quite large photo sizes (forget exactly) but it is quite large and then they reduce them at their end for publishing.

No help with your first point but may explain the 72. [:)]

[Will]

[quote user="Russethouse"]

 I've always believed that the dpi for any photo intended for print (magazine) should be 300 minimum...

[/quote]

Absolutely correct. The bit that is often missed off that dimension is 300 dpi "at printed size".

Therefore if your image is to be reproduced at, say, 6in x 4in, you need a resolution of at least 1800 pixels x 1200 pixels in order to achieve the correct dpi. 

If your image is measured at 72 dpi, which is perfectly common, then you need to check the pixel size. As long as it's a minimum of 1800 x 1200 it will reproduce in print perfectly OK. For your 2.85 x 4 example, you need resolution of at least 855 x 1200.

I wish that PR companies who send images for printing would realise that simple rule. You can't just grab something off the web and resample it to 300dpi; a 640 x 480 image is only good for printing (landscape format) at a maximum width of 2.13 inches - i.e. less than single column width in a typical magazine. Conversely, you don't necessarily need multi-megapixel photographic equipment to produce print-quality images. I find that a 6MP camera with a top-quality lens (like my Nikon D70S) gives far better results for anything smaller than a full-page front cover shot than a compact with double the resolution.

[Russethouse]

 Thanks Will, so it looks as if that website  will be useful ? There are several of us working on the  Club mag and I'd like to send the link to them so they get an idea whether the images they are using will be Ok and at what size max ( 2.85 x 4 is a pretty good size for us - our membership is mainly 50 years + and sometimes + + ! and they hate postage stamp size pics ) Its mainly items rather than scenery....