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Thread ID: 47899	2004-08-08 10:57:00	Irfanview - photos appearing grainy	caffy (2665)	Press F1

Post ID	Timestamp	Content	User
259619	2004-08-09 06:01:00	My Irfanview Caffy, works fine without any problems you have. Strange for such a good program. Maybe as others have suggested, it is an older version, or corrupted. Possibly an uninstall, get the latest version and install that may help. > > Shrink the dimensions of the pic, and leave the > resolution static, or even increase if you want to do > what you say There seems to be some confusion here with advice given to Caffy. The dimensions of the image is the resolution. e.g. 2048 x 1536 pixels = 3.1megapixels, Shrinking these dimensions will reduce the resolution & the file size. Differing amounts of JPG compression will also reduce the file size, and the quality if too compressed. It's all very confusing, as is DPI which is mostly significant when printing the images. This site explains it very well: www.microscope-microscope.org	Bazza (407)
259620	2004-08-09 07:13:00	What is the latest version of Irfanview? I currently have Irfanview 3.90, downloaded a few months. It is a good programme - I think I have changed something in there, I remember saving a photo in GIF format, plus lowered the DPI setting to maybe 50 (or lower). But since then, the DPI has been on 72, and I have been saving photos in JPEG format. Photos' still appear grainy... I've checked in Photoshop (with same settings - size, DPI etc) and the quality is much better. Do you think I should uninstall Irfanview and download again, etc, and see if it makes a difference?	caffy (2665)
259621	2004-08-09 07:17:00	> What is the latest version of Irfanview? I currently > have Irfanview 3 . 90, downloaded a few months . Meant to say: downloaded it a few months ago .	caffy (2665)
259622	2004-08-09 07:28:00	Latest version is 3.91 and a load of plug-ins as a separate download.	zqwerty (97)
259623	2004-08-09 08:37:00	caffy as Bazza has said, DPI has nothing to do with screen resolution and how viewable the image is. Although, primarily about scanning this site (www.scantips.com) also has some useful info on images, DPI, resolution and what it means to your video, screen, scanning and printing of images. Cheers Murray P	Murray P (44)
259624	2004-08-09 09:35:00	Caffy, will you help us to help you? To understand more, have you looked at the site I suggested, and the site Murray suggested? These will help you to have a better understanding of image files & resolutions. You later ask if you should get the latest version of Irfanview. Why not? Thats what others and I have already suggested.	Bazza (407)
259625	2004-08-09 11:45:00	thanks for those websites, I have read them and understand more about the DPI and resolutions . I still felt that the problem was somewhere in the default settings, but since I can't find that, I downloaded irfanview 3 . 91 and hey what do you know, the problem has gone! I can reduce the photo size, and the quality remains exactly the same . I am still not sure what went wrong before? I'd like to know, so I avoid this problem in the future . All I was doing was making the photo small, by halfing it, and then halfing it again (you know that option in Image Resize window?) . Wasn't touching the DPI or anything . Before it worked fine, but after saving a photo in GIF format, things were never the same again!! :( Anyway, if no one is able to help me about this, then don't worry - as the problem doesn't exist anymore . thanks for your help guys, caffy :)	caffy (2665)
259626	2004-08-09 12:46:00	Jpegs are better for photographs, particularly if you want to compress or reduce the file size for emailing or viewing them online. The images will definitely be reducing in quality as you reduce their size because the only way to make them smaller (in KB or MB terms) is to remove data from the file, but, unless you make them quiet small (in size) it will not show up on a monitor. That may be a different matter if you want to print them at a reasonable dimension or actually blow them up to say, full screen dimensions where the actual size in mm or inches of the image and DPI become important. Cheers Murray P	Murray P (44)
259627	2004-08-09 15:28:00	Hi Caffy, The problem with altering the size of pictures is that if you halve the length and height, you wind up with 1/4 of the number of pixels, if the original was 72 dpi, and so is the new file, then you have the pixel count at 25% of the original. This is not a great way to retain the original information, as when you expand the picture by what ever means, you will be very low on data to convey the original image. Assume the original was a 10" x 8" picture, at 72 dpi. You have 10 x 8 x 72 = 5760 pixels, each with whatever colour depth is applicable. 256 colours, 16 bit, 24 bit or whatever. This makes up your file, and as you can see, it can get quite large. If you halve your picture size, to 5" x 4", still at 72 dpi, you have 5 x 4 x 72 = 1440 pixels. This will look pretty much the same if you print them out at their nominal size. Unfortunately, if you try to restore the small image to it's original size, either on the screen or the printer, you are going to have insufficient data to restore the original appearance. Doubling the little picture's size effectively gives it a resolution of 36 dpi, it would be a rather unusual monitor or printer that didn't show that as "grainy". Vertical and horizontal lines will not appear too badly - our eyes seem able to adapt to that quite well. Diagonal lines, or colour changes will not look too good - especially if they are close to the horizontal or vertical. Some programs are very effective at "making up" the missing data, so the picture "Looks Good". If that is what you want, then no problem. However, any change from the original is distortion, and to those with "Golden Eyes", it is an abomination. Not having "Golden Eyes", I don't know whether that would be a curse or a blessing. I do find "restored" images of this kind particularly unconvincing on the sky shade graduations in particular. My problem. The jpeg (Joint Photographic Experts Group) came up with their file system to overcome this when storage and transmission was more of a problem than it is now, and it has evolved since then. It still results in data loss, but not as much as simple scaling does. It is a file resizing method optimised for photographs, and as such deserves it's popularity and almost universal acceptance for medium quality file moving/storing. It is not a good system for files that will require any further processing, it is just for transmitting finished images to printers, or via the web. If you want high quality graphics handling, you will find why graphics systems are priced right up there with gaming systems. One area requires speed, the other requires fidelity as the goal. Both require $$$$. If you need a coffee break, scan an A4 image at 2400 dpi and take your time with the coffee. It is a LOT of data. I was told by a fellow I respect that a medium quality 35mm photographic slide has in excess of 35 MB of information, so your mid-range (i.e. medium quality) digital camera is a bit short of being a threat to a film camera. Not just yet - but it will happen I imagine. Simple rule of thumb, store and manipulate your image at the highest uncompressed resolution you can afford in terms of file size, then reduce it appropriately to print or send. If you wish to search a bit on "jpeg" as a topic, you can find more than you would ever wish to know about it :D R2	R2x1 (4628)
259628	2004-08-10 12:13:00	Thankyou R2 for that explanation. I've been trying to understand your logic. Maybe you can help. AFAIK a digital image does not have dimensions in "inches" as you suggest in saying a 10" x 8" picture at 72 DPI = 5760 pixels. The dimension or resolution of an image is expressed as # of pixels across x down. There is no relationship to inches or DPI, until one prints the image. Then the DPI is determined by the # of linear pixels of the image, & the inch size you decide to print. Scanning a document is similar, in that the original has inch dimensions & the chosen DPI will determine the resulting pixel/resolution. Displaying images on the monitor is another thing. This is where people get confused with DPI. Images dont have DPI. The screen resolution you select for your monitor determines DPI, or more correctly the PPI, usually 72, which displays a typical image of 800 pixels wide to the width of the screen. Your advice to store images at the highest uncompressed resolution is spot on. Reducing file sizes for sending as you say is recommended, but not for printing. Good quality printing needs the best resolution least compressed image file. The printer software/driver will translate the DPI according to the inch size of the print you select. Thankyou R2 for you help & advice. Any comments welcome. Cheers.	Bazza (407)
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