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(E-Mail Removed) wrote:
> I owned the camera over a year now, but have just learned to use it
> recently (after reading the instruction manual)
> I have some questions which I hope someone can provide answers in
> "layman terms".
> What is exactly the extended zoom feature in Lumix FZ18? Is this
> still considered as "optical" zoom. I assume that this is not "digital
> zoom" (because FZ18 still have 4x digital zoom on top of the 18x
> optical.
> It appears that this option has something to do with reducing the
> resolution for the sake of getting more optical zoom feature. Could
> someone explain in simple terms? How this affect the picture quality,
> in particular if I usually only print photos to max 5"x7" sizes. Most
> of the time it will be postcard size of 3.5"x5".
> The manual said that the FZ 18 has a 18x optical zoom feature
> (equivalent to 18mm to 504 mm). This is however based on picture size
> equivalent to 8 MP (for 4:3 ratio). However, if I select the
> resolution to only 5MP, I can zoom in to 23x. If I choose resolution
> 3MP, I can zoom into 28.7x.
> 8 MP is equivalent to 3264x2448 pixels, 5 MP is 2560x1920 pixels, and
> 3MP is 2048x1536 pixels (for aspect ratio 4:3).
> What do you need to print 5"x7" size photo, 8"x10" and 11"x17"? Is
> 3MP good enough for 8"x10" photo? 5"x7"? I know that my computer is
> only set to 1024x768 resolution.
> If this is the case, I can just set my camera to 3MP and enjoy a 28.7x
> zoom ( from 28 mm to 804mm)! I am still assuming this is NOT digital
> zoom.
> Could someone comment on this? Thanks

In extended zoom, the camera is using the lens at it's maximum focal
length, with no digital magnification/zoom. So in theory it is still
"optical" zoom with no reduction in resolution of the subject.

The files that the camera saves in extended 5MP, 3MP, etc are exactly
the same image that it would save if set to 8MP-standard, however, it
will have been cropped in-camera to show only the centre. That is why
the image you view looks more magnified, when infact it's just the
central region of an 8MP image. Ultimately, you would be better off
saving at 8MP and cropping it in a photo editor for the desired detail.

When cropping the image you can look at it's final pixel dimensions and
judge what size to print it at. There is not really any point in
printing photos at more than 300 dpi, unless you view them with a
magnifying glass. (I submit scientific images for publication, and the
journals ask for 500 dpi. Scientists do use magnifying glasses to view
them.) Divide the image dimensions of your photo by 300 to see how many
inches it will reasonably print at.
For example, the 3MP images at 2048x1536 should be fine for 6.8"x5.12" etc.

I don't use my fz18 in extended mode, I prefer to crop the original 8MP
images. It can be handy if you are using the device as a telescope
though , but not as a camera.
Hope that helps.
DavidM