Ronniebootwest Posted January 7, 2005 Report Share Posted January 7, 2005 In my early days of using PTE I learned that the optimum size of an image was 1024 x 768 with a resolution of 72. It was also recommended by most experts to save the image as a jpeg file with a compression setting of 6. All of this was obviously to keep the size of the file to a minimum because, in those days, PTE would often crash if the file sizes were to large.Recently, I have been experimenting with larger file sizes and less compression when saving my images in Photoshop. The resulting .exe files all seem to run without a hitch so my question is this, What is the recommended file size/resolution/compression recommended now?Ron West Quote Link to comment Share on other sites More sharing options...
Ian Posted January 7, 2005 Report Share Posted January 7, 2005 Hi RonYour points are mostly true, except for the bit about "72 dpi" - this setting is not relevent for projected or screen images as the output device will run at a fixed pixel dimension. Most digital projectors in general and club use are currently XGA resolution - ie 1024x768 pixels. That's why it is still advantageous to have your show images at this dimension as they will fill the screen on a 1:1 basis.Anything larger than this size, and the video card will have to "hide" the pixels present in the image that it won't be able to display. Most of my sequences I have made at 1024 pixel width, however some of the newer ones I've made at 2048 width. When the video card has to decide which pixels to discard to fit on to a 1024 display, it is a fairly easy calculation to hide every alternate pixel, and the projected results are very good. If you choose a size that is not easily divisible, then you are un danger of getting "jaggy" edges where an uneven number of pixels get hidden.The reason I've made some at 2048 width is that these shows will still look sharp (possibly sharper) as and when hardware improves and 2048 pixel projectors become generally available.The other thing to remember is that if your sequence is to be played back on a variety of equipment, it is still worth considering that some hardware may struggle to keep pace with larger files, especially if played back from a CD Rom.I'm doing a show/seminar at the Waves AV Group in Bath on 22nd Jan, and at Cheltenham CC on 3rd March so if you're in the area come along and say hello!Ian Quote Link to comment Share on other sites More sharing options...
ContaxMan Posted January 7, 2005 Report Share Posted January 7, 2005 The idea is to have the image pixel dimensions the same as the visible area of your monitor - this is where the 1024 x 768 figures come from. The 72 figure is completely irrelevant, representing the approximate screen resolution of Mac monitors. When you use Photoshop to resize images, just enter the pixel dimensions you want and ignore the resolution figure.For a detailed discussion of the "72 myth" see:Resolution explainedIf the article doesn't convince you, nothing will!As for compression, I use "Save for web" and choose the amount to use "by eye". Generally this gives a jpeg of around 250 k, leading to a show which run fine on my ancient laptop. My guess is that it is the music rather than the images that cause "glitches" - perhaps Oleg might enlighten us? Quote Link to comment Share on other sites More sharing options...
Gérard de Lux Posted January 7, 2005 Report Share Posted January 7, 2005 Thank you, Roger, for having pointed the way to my explanations I regret that these pages are the only one in English on my website.I fully agree to what Ian said, it is very wise and important ! I would just like to add that it is very important that whatever the size of the image is, it should be divisible by 16 ! This is the safest way to ensure that the image quality isn't reduced when the graphic card has to downsize a big image as Ian explained.Cheers Quote Link to comment Share on other sites More sharing options...
Ronniebootwest Posted January 8, 2005 Author Report Share Posted January 8, 2005 Why should it be divisable by 16? I am curious! Please explain.Ron Quote Link to comment Share on other sites More sharing options...
bjc Posted January 8, 2005 Report Share Posted January 8, 2005 ContaxMan – I’ve just had a quick look at the ‘link’ you posted. Very informative ~ thank you ~ but sadly wrong on several counts. And likely to cause increased confusion in those uncertain of the facts. Of primary concern was his (?) use of the term ‘dpi’ when expressing the physical size of an image on paper. Very misleading.PPI ~ refers to the physical size on an image on paper, and to nothing else. Therefore, with an image set to 100 PPI, each 100 pixels of an image will span 1 inch of paper. 1000 pixels @ 100 PixelsPerInch = 10 inches etc.DPI ~ refers to the number of DOTS of ink (Per Inch) that an inkjet printer lays down onto paper in order to reproduce the image.The two are not inter-related in any way.If a 1000 pixel wide image was set to 100 PPI then (as mentioned above) it would be reproduced 10 inches wide on paper. With the inkjet printer set to 720 DPI the image would be still 10 inches wide on paper ~ likewise at 360 DPI and/or 1440 DPI ~ all that would change would be the number of ink dots laid down by the printer to render the image. The size an image appears on a monitor screen (website, email or slideshow) relates in real terms to neither PPI nor DPI, but to the physical span of a set number of pixels across the particular monitor screen in question. For example ~ your monitor screen set to 1024x768 will not necessarily display the exact same physical screen width as my monitor screen set to 1024x768 ~ therefore an identical image viewed on our two monitor screens would not necessarily be seen at exactly the same physical dimensions ~ the only constant would be the ‘percentage’ of screen-width spanned.bjc Quote Link to comment Share on other sites More sharing options...
ContaxMan Posted January 9, 2005 Report Share Posted January 9, 2005 "PPI ~ refers to the physical size on an image on paper, and to nothing else. Therefore, with an image set to 100 PPI, each 100 pixels of an image will span 1 inch of paper. 1000 pixels @ 100 PixelsPerInch = 10 inches etc.DPI ~ refers to the number of DOTS of ink (Per Inch) that an inkjet printer lays down onto paper in order to reproduce the image.The two are not inter-related in any way."Yes - I appreciate this. I suspect that this is partly due to the translation (the original is in French - as I can't speak this very well, I can't check it)."The size an image appears on a monitor screen (website, email or slideshow) relates in real terms to neither PPI nor DPI, but to the physical span of a set number of pixels across the particular monitor screen in question. For example ~ your monitor screen set to 1024x768 will not necessarily display the exact same physical screen width as my monitor screen set to 1024x768 ~ therefore an identical image viewed on our two monitor screens would not necessarily be seen at exactly the same physical dimensions ~ the only constant would be the ‘percentage’ of screen-width spanned."Exactly - that's the point I was trying to make. Quote Link to comment Share on other sites More sharing options...
Gérard de Lux Posted January 11, 2005 Report Share Posted January 11, 2005 Hello bjc,I don't really understand your objections because there's no reference to ppi on my page and I fully agree that dpi is only relevant to printing (this is the point I make systematically since 3 or 4 years), unless there has been a translation bias (my original is French as pointed out); this is why the only relevant unit when taking about image size on screen should be pixel (like 1024x768 for example).Anyway, here is another interesting link say no to 72 dpi ont he same question ant this one is original English; from the same website, there is also this series, and theoretically we say exactly the same thing unless, again, some translation problems.CheersGérard Quote Link to comment Share on other sites More sharing options...
bjc Posted January 11, 2005 Report Share Posted January 11, 2005 Hi Gérard,, Please don’t offence at my comments re: your page ~ no offence was intended,,, honestly. Nor was I ‘objecting’ to the content ~ quite the contrary ~ it is, as I mentioned, very informative.However, it is my considered opinion that PPI :-(the unit of measurement that describes the ‘physical’ dimensions of an image when printed ON PAPER)and DPI :-(the number of ink-dots placed on the paper – per inch – by the inkjet printer to reproduce the image)should not be mixed up ~ as this can lead to even more confusion in the minds of those who have not yet fully understood the two conflicting parameters. On your page you mention :------------------------------------------------------------------------------------Take an image measuring 2240 x 1680 pixels (what you would get from a 4MP digital camera); if you print it at 300 dpi, you will get a picture 7.5 inches (19 cm) wide by 5.6 inches (14.2 cm) high; if you print it at 100 dpi, it will come out at 22.4 inches (57 cm) by 16.8 inches (42.7 cm). By replacing ‘DPI’ with ‘PPI’ this would make sense.An image can be printed out with the printer set to 360dpi ~ 720dpi or 1440dpi – yet the physical dimensions of the image will not change. As it is the PPI rating of the image that determines it’s physical size on paper ~ not the DPI settings of the printer.I will admit that the confusion between PPI and DPI is wide spread ~ even my humble Epson Flatbed scanner offers scanning resolutions measured in DPI !? Which, of course, is totally bizarre when you consider that the resultant images it produces are scaled in PPI !?My input was made purely in an attempt to draw a clear dividing line between PPI and DPI ~ Pixels-Per-Inch and Dots-of-Ink-Per-Inch ~ once those two concepts are understood then I think the confusion over the issue quickly disappears.I hope you agree. bjc. Quote Link to comment Share on other sites More sharing options...
Maureen Posted January 12, 2005 Report Share Posted January 12, 2005 This must be one of the most popular discussions on this Forum !Has cropped up so many times - earliest was Dec 2002 on this current Forum and even many times on the previous one.Think all the web links explain it very clearly. Hope Ron isn't feeling too confused ! Love your Status Quo pics bjc ! How about a "Quo" sequence ? BW Maureen Quote Link to comment Share on other sites More sharing options...
Ronniebootwest Posted January 12, 2005 Author Report Share Posted January 12, 2005 Hello Maureen and all you other contributors to this thread.No, I am no longer confused because the subject matter has been so totally covered with some excellent explanations. We all have to learn and that is the beauty of this forum; so many members who are happy to share their knowledge with us. Many thanks to all of you.Ron Quote Link to comment Share on other sites More sharing options...
Barry Beckham Posted February 10, 2005 Report Share Posted February 10, 2005 bjcAre you confusing all these good people with DPI and PPI? Now what did you say again?I don't do technicalBarry Quote Link to comment Share on other sites More sharing options...
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