LCD Screen Zoom.

On the K20d when we zoom in to check if we are in focus, at what zoom level is equal to 100% on a computer screen any idea's please.

And if this has been asked before I'm sorry but could not find it in the search.

That is something I have been tinkering about as well, Tel, and I have done some calculations:

Knowing that the LCD has 230000 pixels, and assuming the screen has a 2:3 ratio, the resolution should be about 392 x 588 pixels.

For my K200D, which has a maximum resolution of 2592 x 3872 pixels, I should have a 1:1 presentation at 6.6 times zoom (magnification). That should be the best size for evaluation of sharpness, imo.

I did read that 11x on the K20D was 1:1, but looking at Terry's calcs I'm now unsure...
Matt

Interesting, and while on this topic any idea what the old *ist DL2 would be as we can't go 6.6 as I can tell.

Thanks,

It will also depend on whether the magnification is describing a linear (ie magnification on one side) or an area... that would make a big difference.
I'm really curious now... and will have to work out a way of calculating it reliably...
Matt

Curiosity is a wonderful thing, Matt

After doing another test, I found that the LCD screen ratio is 1.333 rather than 1.5 as assumed above. This gives approximately 416 x 554 pixels for a total of 230000 pixels. (Would appreciate if anybody could confirm this).

The images in my K200D at 2592 x 3872 pixels would then display 1:1 at about 6.2 x zoom. For the K20D at 3120 x 4672 a 1:1 display should occur at 7.5 x zoom. The closest I can get is 5.7 or 6.7.

Wouldn't it be nice if Pentax had provided a 1:1 stop in the zoom range?

The magnification you need is x16, this is the exact magnification you need to look at for 100% of the image.

I'm not sure why it goes upto x32, its pretty pointless to me.

From where do you have that information, if I may ask?

From experience and common practice.
If you take an image that you know to be perfectly sharp you will find the magnification limit jus' by simply lookin'. Beyond x16 and at x19 the image is fuzzy and unsharp.
It was x16 on my other cameras also. Its not rocket science.

But that wasn't the question asked which was "how far do you have to zoom in to get 1 pixel on the preview screen = 1 pixel in the image". The maths suggests that somewhere in the region of 6 to 7 times depending on sensor resolution.

Curiosity plays again . I just had to make a couple of test shots:

This is the full picture at 3872x2592, downsized to 800 pixels:
[IMG]http://i233.photobucket.com/albums/ee91/terje-l/IMGP4887_edited-1.jpg[/IMG]

From the original I reduced (cut) canvas size to 554x416:
[IMG]http://i233.photobucket.com/albums/ee91/terje-l/554x416.jpg[/IMG]

So this should be a 1:1 pixel-by-pixel image. And it corresponds very close to what I see on my LCD screen at 6.7x zoom.

I believe that proves my theory that this is the closest you get a pixel-by-pixel preview on the LCD. (For what it's worth )

You are correct, Kris, paulyrichard answered a totally different question.

No problems with sharpness on that photo Terry...

What also needs to be taken into account is the resolution and size of the PC screen. You could have a small 10" screen, or as a friend uses, a 42" widescreen. You can still get very 800x600 LCDs up to 3500(ish)x2160 ...

Everyone will have a different result.

We're talking about the screen on the back of the camera. The question was: what zoom factor do you need to use on the camera to get a 1 pixel = 1 pixel image. The size of the laptop screen is thus irrelevant, although of course the model of camera is (e.g. the K10D v. the K20D).

Best wishes, Kris.

So do we know what the answer is for the K10D?