LCD Screen Zoom.

The official specs from Pentax state:-
Type: TFT color LCD monitor, brightness adjustable, Color adjustable, Wide angle view
Size: 2.7 inch
Dots: approx. 230,000 dots

In the same spec sheet you will also notice that the sensor is defined in Pixels which is approx 15.07 Megapixels (only approx 14.6MP are effective).

Theses spec sheets can be checked at any official Pentax site. using the word 'dots' is not a typo, it's an industry standard phrase to make things sound better! Check the specs for some of the C & N models and you will find 3" VGA screens with approx 920,000 dots.

VGA = 640 x 480 Pixels, which is 307,200 pixels
307,200 Pixels x 3 = 921,600 dots, which they call approx 920,000 dots.

So whilst you are right in suggesting that LCD's are normally specced in pixels, when it comes to that magic of marketing '76,800' pixels does not sound as impressive as 'approx 230,000 dots' same as 307,200 pixels does not sound as good as 'approx 920,000 dots'.

We went through similar marketing speak with monitors (24" but only 22" visible) and we do with hard drives too (the size of a GB is conveniently rounded down).

This confusion is not helped either by the fact that Pentax just will not put the resolution of the LCD itself in their spec sheets (it's not something to boast about in comparison), but they do put every resolution the sensor is capable of because at the time of release, it was a market leader, so they boasted about it.

The sooner they make the marketing clearer, the less confusing it will be for the end user.

This is interesting as I've never used the camera screen to check focus. I use the viewfinder to see if it has snapped into focus at the correct point.

I use the screen as a quick check for closed eyes on portraits and maybe to see if the composition is right.

I've never found camera screens good enough to check sharpness. 230,000 dots (often incorrectly stated as pixels) isn't really enough. There are some 900,000+ dot screens now that offer some promise.

I hear what you say, Unlocker. However, that does not explain how I can see the correct 554x416 pixels image at 6.7x zoom if my screen is only 320x240 pixels .

The whole exercise was about finding a zoom factor where pixel meets pixel, to avoid interpolation one way or another. Anyway, that's where any LCD screen shows the sharpest image.

Hard drives are different, because all memory sizes are based on the binary rather than the decimal system (1 kilobyte = 1024 bytes).

Ok... I'm going to throw a REAL spanner in the works here

First of all, I found out how to get an edited JPG back onto the camera so it will display it! Woohooo!
1. Go here: http://www.panasonic.com/business/projectors/ss_software.asp
2. Download "JPEG Converter [exe]" and install
3. This little tool saves a DCF compliant JPG to the folder of choice

I renamed the JPG files back to "IMGPxxxx.JPG" and saved to the SD card and the K20D displays them just fine



Now, I took a full res JPG shot of a boring scene, took it into Photoshop and put a black-white-black-white single pixel stripe. I did this horizontally and vertically. Ran it through the DCF converter and displayed on the K20D.

What I get is this:
1. x11 shows promise of 1:1, but vertical lines show a checkerboard pattern (presumably because of the arrangement of pixels in the LCD)
2. x14 is the first zoom to show an accurate 1:1. BUT there is the possibility of some aliasing on the horizontal stripe only. Odd!
3. x16 is really fuzzed up with aliasing issues
4. x19 shows some fuzzing
5. x23 and above clearly and reliably shows the single pixel lines... but it's difficult at these zooms to separate ISO noise from real detail.


My conclusion (at least from this test) - use x11 or x14!

I'm happy to email the 10Mb JPG file if anyone wants to test it out... or you can follow the same procedure as me and see what you come up with!

EDIT: added extra observation about x11.

Matt

Matt, please send me the jpg so I can have a go and check it.
Whats the best way for you to send me please? do let me know

Hi Amin,
You can download it from here:
http://www.photon.me.uk/pu/K20D_FullZoomTest_IMGP4001.JPG
Be warned - it's 10Mb!

Hopefully you can download it and rename it to just "IMGPxxxx.JPG" and stuff in an appropriate directory on your card (usually DCIM, but may be date related depending on your custom settings on the K20D)

Let me know what you find out!
Matt

Wish I could explain your example, but wouldn't know where to start unfortunately, all I do know is that by trying to find the 1:1 pixel level, you do have to know what pixels you have to start with, which because of the marketing confusion just isn't clear.

My Hard Drive analogy again is a marketing one, we know the binary sizes, but we are sold the decimal sizes, therefore again getting less than we would expect!