A compressed Tiff or Img file of 1000x1000 plane white is only about 4 bytes because one byte gives the colour and the other bytes give the run or number of repetitions. Fax uses this Hoffman coding. It is lossless. You could zip an uncompressed TIFF image file with the same effect. Its all mathematics. With a lens there is a fundamental limit due to diffraction quite apart from the figure of the lens. A fast lens will have higher resolution than a small aperture. There is a lovely function sin(x)/x that gives a curve with a peak with ripples around it and all lenses has it, with bigger lenses this curve gets tighter. I recall also the "error function" and it is important in the resolution of telescope images. I once did some work trying to resolve the discs of stars. The solution was an array of telescopes first used in radio astronomy. Like other physics the construction took many years. To see small things you need very big things over a long integrating time... the search of ET radio communications is like that. People did not like the observational results... I received a 30 year non custodial sentenced under pills for my work instead of hanging me! It was based on Shannon's work but the judge lacked imagination and wars are fought over it. The present conflict around Islam is related also. Life has been very hairy just now even in Britain. They will probably come again on Tuesday. Science itself is under attack. Sorry.. but the little compact digital ... Photography is difficult here, even people who snap their children have been prosecuted and the thought police are a reality. They have pills for that too. They found that my weapon is a camera. I snapped an execution in a church... I was incarcerated and pilled for snapping a "flying saucer" near my home. And another local lady was held and pilled for reporting the funny little space aliens that ran into hr shop and stole things, I saw and photographed them and they were warm to touch... Other witnesses were executed by brain destruction on the spot and of course I "lost" the digital files. I avoid leaving my home now. But the thought police know my address with their pills and their knives. So photography can be dangerous. You have to know who your friends are and which shops to enter and answer the questions correctly. Dr Chris, London, UK. -----Original Message----- From: owner-photoforum@xxxxxxxxxxxxxxxxxx [mailto:owner-photoforum@xxxxxxxxxxxxxxxxxx] On Behalf Of karl shah-jenner Sent: 24 August 2014 06:23 To: List for Photo/Imaging Educators - Professionals - Students Subject: Re: Large print - quality issue Chris writes: > You cannot put in detail that is not there. It is empty magnifications you > get it in optics also. As you say Chris you cannot, but you certainly can make it *look* better when you increase it's size, and perception for pictorial pictures is pretty much everything. (However I will grumble if accuracy is the goal and can point out many flaws where added data can lead to misinterpretation of actual data) However, how you add this fictional material is pretty important go get the look right. Cameras use some complex and advanced algorithms to add this data - by way of illustration think of it like this.. you need to make an image bigger so you just duplicate the same data you already have and stick it between the existing pixels - this is the origin of that advice regarding photoshop - increasing the size in small increments adds it slowly - it's a very, very basic method and a fundamental flaw of Photoshop that it had (still has?) such rudimentary methods of upsizing images. By way of example see here for a page I put together a long time back http://members.iinet.net.au/~shahjen/ebayimages/sharpening.html If you look at the grey panels in my examples - the scroll bars - on the right of each image pane you'll see a checkerboard pattern instead of a smooth grey region - this is because upsizing is basically stupid. I used these screenshots in place of any other pictures because they're recognizable and it's clear as daylight what the upsizing is doing to the image As this* guy says though, some algorithms are designed to be more intelligent than that and will actually look at the data in the image, work out what is important, where patterns may exist, and from this they can predict what the missing data should be and armed with this, they'll do a good job of adding new stuff. Some algorithms are better at different tasks than others so it's worth not just using one for everything but instead experiment fo find the best one for the task. ( * http://web.archive.org/web/20060307093804/http://www.interpolatethis.com/int erp.html - his page is gone now - a shame. People need to understand that the internet is a bit more ephemeral than we've been led to believe. Authors grow tired or pass away so their internet writings are a bit like books .. it ain't like they'll be topping up their pages with new data all the time, and eventually it wont be accessible any more) Downsizing is another case where intelligent algorithm use should be used - do it wrong or use a stupid one and you end up with those dreaded jaggies.. there is NO reasson anyone should see jagged edges in a downsized image (even though you see it all the time!) - it's just that a resize function has been applied instead of resampling with an algorithm - and as you can easily imagine, taking unintelligent bites regularly out of a descending slope and you end up with a staircase - that's how it happens > If you want detail do not use jpeg. Other forms of compression are > available > like TIff and Gem. These are lossless. Jpeg can be lossless too. Jpeg has drawn a lot of criticism because of the way it gets used - it is NOT inherantly lossy, it's that the staple, lauded and revered image editing programs are lazy and resting on their laurels - Photoshop doesn't handle jpeg losslesly , that isn't the fault of the jpeg! Other image programs can. Yes, if you rotate a jpeg it looses data in Photoshop - not so the case in Irfanview if you use their lossless jpeg transformations - so that is a clear example. I'd also add that jpeg is actually a container for a bitmap, just as zip is a container for whatever you stick inside it. How crushed a jpeg can be is at th discretion of the user. What jpeg is really good at is intelligently eliminating redundant information for the purpose of storing the image in a smaller space. Picture a 6000x6000 pixel bitmap that is pure white. A bitmap, tif and others will store every single pixel. A jpeg will record the colour data of one pixel and a map of where they all are and store that instead - obviously the image file will be a lot smaller (the bitmap will be 105,469 Kb, the jpeg at maximum quality will be 202,Kb, and interestingly, an 80% jpeg will be the same size - a clear demonstration that there was no data loss whatsoever) a footnote to the matter of resizing and data interpolation - on the basic math of camera digital image capture, there is utterly no way the cameras can get the detail recorded in some images with optics and sensor alone.. some seriously intelligent interpolating is going on - the resolving power of the lens which everyone knows contributes to the resolving power of the image capture system should by it's self ensure that most images are more degraded than they actually are, but the sensor it's self is incapable of the capture we think it is because of the mathematical concept of a Nyquist limit. On a single plane, the resolving power cannot exceed 1/2 the sample rate meaning a 2000 pixel long image (of 1 pixel) cannot resolve more than 1000 pixels accurately .. but on a 2 plane system X, Y, you have roughly only 1/3 of the resolving capacity. Couple that now with the imprefections of a lens and your digital capture system and you'll see there's no way we can be getting the images we do unless some clever algorithms are adding data that is not visible to the system..