As with most things, there is good and bad with TFT screens. Perhaps I can repay a little of the wonderful free advice I've had from Andy and Kevin and others here about digiscoping (something I know nothing about) with a short primer on screens - something I have some expertise in. (I've been in the computer game for most of my working life, one way and another.)
On the good side:
- Space saving
- Lack of glare
- Zero flicker
- Zero radiation
- Clarity (sometimes - see below)
On the bad side:
- Cost
- One fixed-pitch resolution
- Slow refresh rate
- Poor off-axis performance
- Mediochre performance in bright light
- Horrendous repair costs
- Huge variation in quality between makes and models.
Not all of these things apply to all screens, of course, and there is a
huge variation between different makes and models. TFT screens can be wonderful but I can't stress strongly enough that this applies
only if you have the right screen (which will no be cheap), and your usage is well-suited to TFT - some people only do things that TFT screens are good at, other people want to do things that, in general, TFT screens are
not good at.
Some rules of thumb to bear in mind:
- TFT screens have a fixed screen resolution which cannot be adjusted. For example, the one on my front desk at the office runs 1024 x 768. It cannot run a higher resolution under any circumstances, and although it can do lower resolutions in theory, in practice these are done by software interpolation and there is simply no way to preserve things like the shape of a font or a colour photograph when your screen is taking the signal intended to light three pixels and turning it into 1.864 pixels. At any resolution bar the design resolution TFT screens look dreadful.
- If you play games much, especally shoot-em-ups, TFT is too slow to give you decent frame rates. If you already have a Gforce 4Ti and you lie awake dreaming about a top-end Radeon or a Gforce FX5900, then you don't want a TFT. (If you don't know what those things are, then this doesn't apply - you are not a serious gamer.)
- If you have children who want to play games and edutainment things that run in any resolution other than the native resolution of your intended TFT screen (or if you want to play Thomas the Tank Engine!) then TFT is not for you.
- Does anyone in your family wear reading glasses? Before you decide on TFT or CRT, make sure that they can get comfortable with it. Some people who wear glasses can't find a seating position that lets them look at the screen and at the paperwork on their desk without putting the glasses on and off all the time, and this makes the computer unusable for them. TFTs and CRTs are different in this respect, so check first. (Or be prepared to spend the next three years sleeping in the dog's kennel.)
- A good TFT screen is simply brilliant at its design resolution. Sharp, clear, restful on the eye. With a good TFT, there is no middle ground: the display is near-perfect at native res, poor to very poor at lower res, and there is no display at all at higher than design res.
- The latest generation of 450:1 TFTs are superb. I have not seen the Illyama (not sure if we get them here in Oz) but I have sold several of the 17" Mitsubishi 450:1s and I was very tempted to take one home - the only thing that stopped me is that I really want a 21 and they don't make a 450:1 21" TFT yet. (Oh, and the small matter of having my eye on a Swarovki scope and new camera, and not wanting to take out a second mortgage!)
- If you don't play games much, most of your work is text and picture based, and you are happy to be always stuck in the design resolution of your TFT monitor (1280 x 1024 or whatever), then you should consider one.
- TFT screens are almost impossible to repair. Once the warranty has run out, if it goes wrong, it is reasonable to expect that you will have to simply buy a new one.
- CRT screens vary in quality a good deal, but even the cheap no-name ones are quite good.
- TFT screens vary in quality by a huge amount. Cheap no-name ones are often terrible!
- Remember Tannin's Law: If it looks good, it is good. Let your own eye be the guide. Buying a monitor is like falling in love: if you are asking yourself if you really like it or not, you don't really like it. Don't say to yourself "I really like feature X and .. hmmm ... yeah, I think feature Y is OK". It is quite easy to talk yourself into thinking that a general vagueness of picture is "just a matter of getting used to it". It's not. If it doesn't look wonderful, walk away. You will never get used to it.
- Don't make the mistake of comparing a 17 inch TFT with a 17" CRT. Compare like with like in dollar terms. (Err ... pound terms ... whatever.) For about the same money, you can buy a good quality 17" TFT or a top-of-the-line 21 inch CRT. For the same price as a quality 15 inch TFT you can buy a premium-quality 19 inch CRT.
- Sell with graphics, buy with text. Any monitor, even that dreadful old 14 inch thing in your back shed, looks great when you load one of Andy's pictures and zoom it up to full screen. One of the best ways to sell really poor-quality monitors is to put a screenshow of nice, bright colour pictures on it. Most people will think how nice the pictures are and never see the flaws in the monitor till they take it home.
- If you want to see how good a monitor really is, put up a screen of plain, black on white text, the smaller the font the better. (An easy way to get a screen full of small text on most computers is just to maximise a folder with lots of files in it up to full screen - the Windows folder is usually suitable.)
- Look at the fine print. Get really close to the screen - six inches or so, and look at one individual letter. Is it sharp? Is it crisp? Can you resolve the individual dots that make up the letter? Now do the same thing on a cheaper screen. A cheap screen will give you blurry, fuzzy dots, or no dots at all, just a vague area of darkness. Sure, you want to see letters, not dots, but the ability of the screen to show you the individual dots when you are right up close is directly proportional to its ability to show you a crisp, sharp picture when you are sitting at a normal distance from the screen.
- If it doesn't have a three year warranty from a company you trust, walk away.
- CRT screens are bulky and ugly, but they still give by far the best colour balance for professional graphics work. Their ultimate resolution is highter, and they are much more flexible. You also get a much bigger screen for the same money.
- CRT and TFT measurements are made in different ways. Both are measured on the diagonal, but a CRT is the same as a TV: the manufacturer measures the picture tube and rounds it to the nearest inch: a 16.6" tube and a 17.4" tube are both regarded as 17s. You can't measure it yourself without pulling the monitor apart. The actual picture area varies: in most modern CRTs it's about one inch less than the nominal size, so a typical 17 gives you just under 16 inches worth of picture. However, this varies considerably: it is technically challenging to get the edges of the display close to the outside of the tube without distorton and echo effects, so cheaper monitors of any given size tend to give you more bezel and less picture. TFTs are completely different: they don't have a picture tube, so you simply measure the viewable area: a 15.1" TFT gives you 15.1 inches of picture.
- There are two different ways of making a CRT: shadow mask and aperture grille (well known under Sony's Trinitron trade name). Partisans of one camp or the other often claim that method X is superior, which is nonsense. Either method can be used to produce a superb monitor, or a cheap and nasty one. In general, the smaller the dot pitch the better, but this can be measured in so many different ways that it's usually better to ignore it. Be sure not to compare horizontal figures with diagonal ones! Aperture grill monitors use stripes, not dots, so for them dot pitch is meaningless. In any case, the quality of the engineering is much more important. Trust your eyes, not the spec sheet.
- There are two different styles of CRT screen, with names guaranteed to confuse you: perfectly flat which is indeed has perfectly flat glass at the front, and flat, square which has curved glass! (Both retain the traditional bulky picture tube - compare with TFT screens which are only an inch or two thick and are "flat" in both senses.) In general, neither type of CRT is superior, it's a matter of individual taste. It is difficult to make truly flat CRT as bright and precise as a slightly curved one, but on the other hand slightly curved ones always distort straight lines, and tend to have more trouble with glare and reflections. Chose whichever you prefer.
- Picture quality depends on three things: the screen is only one those three things. The second is the cable - yes, the quality of the cable really does make a difference, and it ain't just in theory - at high resolutions (1280 or 1600 and higher) you can see it at a glance. Most monitors come with a cable good enough for that particular monitor, but it's something to be aware of, particularly if you are thinking about using an extension cable or a switch box.
- The third of the three things that determine picture quality is the RAMDAC. This is the chip on the video card that converts the numbers into voltages that the monitor can display. Cheap RAMDACs don't do a very good job of it. At lower resolutions (640 x 480, 800 x 600) it won't matter much, but at 1280 & 1600 and above, it becomes critical, especially with CRT montors, which run at much higher refresh rates. As a general rule, all-in-one computers where the motherboard has the video included (not on a seperate, upgradable card) have lower-quality RAMDACs. Stand-alone video card RAMDACs vary too, mostly with the particular manufacturer. The raw power of the card is not a good guide to the quality of the RAMDAC. With that said, the average RAMDAC is much better today than it was two or three years ago.
- 1280 res & 85Hz is the dividing line: any CRT monitor or video card that can't do 1280 x at 85Hz or more and do it without going vague or fuzzy is - no matter what it says on the price tag - a cheap one. With a CRT, you need to run it at 85Hz or more to get rid of the flicker. (TFT's run at about 60Hz and because they use a completely different technology, flicker is not an issue with them.)
- When you buy a monitor, if you are choosing it yourself (as opposed to buying a specific model because someone you trust says they are good), ask to see it at the resolution and refresh rate you intend to use. Don't neglect this step! If the sales person doesn't know how to do that for you, turn around and start walking till you find a shop where they know something about computers.
- There are three nice things to look for in a TFT monitor: (i) great price, (ii) great picture quality, (iii) good warranty. You can whichever you want of those three things - but only two at any one time!
What do I run myself? I've owned several TFTs and love them, but right now I have CRTs on three of my four most-used machines. I'll probably replace the best one (a 21 inch Mitsubishi CRT) fairly soon and play hand-me-down. I'm torn between the excellent new Mitsubishi 22 inch CRT and the (possibly even better) 17 inch 450:1 TFT from the same maker. Maybe I'll wait till they do a 19 inch 450:1 TFT.
Summary: "cheap" TFTs are dreadful, good ones are wonderful, but they are not for everyone.
