This may be covered somewhere, but I have had trouble finding it.

I'm interested in knowing what the different quality settings control and when they take effect.

Specifically, what is the difference between the "image quality" and "full image quality" parameters. The "thumb quality parameter" seems self-explanatory.

Also, when does this compression take place? Upload time? Caching time? If it takes place at caching time, then I assume that changing the parameters requires the images to be re-cached before you see the change. But if it happens at upload time, is there a way to see any parameter adjustments made without re-uploading all the images?

Similarly, when does sharpening occur? Is it standard to sharpen images BEFORE upload to decrease processor time?

If this is covered clearly somewhere, that would great - just point me there.

In general, I am very impressed with the product. So far the largest disappointment has been the lack of clear instructions.

Thanks in advance!

all image processing is done when the cache is created or when you are displaying full sized images with watermarks.

image quality refers to the image in the cache. Full image quality refers to the image displayed full size (see above)

When you understand all this maybe you should volunteer to write the manual.

well... the humor is appreciated. and i will gladly help out at some point.

so, since it seems difficult to get full explanations and your response is still confusing to me, i'm going to make some statements (partly guesses, partly common sense, and partly based on your response). can you tell me if the following statements are correct:

1. The system creates several versions of each photo (since i am ignorant about how these are named, i'll call them: thumbnail, gallery-size, and full-size).

2. Image processing (compression, sharpening) for the thumbnail and gallery-size versions are performed when the cache is created. the quality of these images is controlled by the "thumb quality" and "image quality" parameters. The higher the number, the higher the quality, but also the larger the file size. Good defaults are 75 and 85, respectively.

3. If you change these parameters, you'll have to reload the cache to see the changes. [Haven't looked into how to do this, but I'm sure it's relatively simple.]

4. Image processing for the full-size version is done [not-sure-when]. This is controlled by the "full size quality" parameter.
[I don't understand if this is also created ahead of time or on the fly when requested. Also don't understand if the timing of the processing is dependent on whether there is a watermark involved or not.]

5. If you change the "full size quality" parameter, you'll have to [fill-in-the-blank] to see the results.

So... hopefully these are easy to answer. If I'm getting on the right track, I'd be glad to write something up since it seems like many novices would/will have similar questions and these types of explanations would really benefit the community. I apologize if these questions seem annoying to the veterans, but it really would be great for the novices out there if these issues were more clear.

[i]1. The system creates several versions of each photo (since i am ignorant about how these are named, i'll call them: thumbnail, gallery-size, and full-size).[/i]
Zenphoto creates only two image types, the thumbnail and the gallery size image that we call "sized image". The full size image is the image you upload. That is basically only altered if you turn on watermarking (I am not used to the actual details).

[i]2. Image processing (compression, sharpening) for the thumbnail and gallery-size versions are performed when the cache is created. the quality of these images is controlled by the "thumb quality" and "image quality" parameters. The higher the number, the higher the quality, but also the larger the file size. Good defaults are 75 and 85, respectively.[/i]
Correct. The cache is created if you view the image the first time in your gallery, then the image is processed to the size set in the options. Or alternativly you can precache, but that is actually not needed since it is done on the fly once.

[i]3. If you change these parameters, you'll have to reload the cache to see the changes. [Haven't looked into how to do this, but I'm sure it's relatively simple.][/i]
We have buttons for clearing the cache. Actually you don'T have to reload the cache. The images with the new settings are then newly made and then used.

[i]4. Image processing for the full-size version is done [not-sure-when]. This is controlled by the "full size quality" parameter.
[I don't understand if this is also created ahead of time or on the fly when requested. Also don't understand if the timing of the processing is dependent on whether there is a watermark involved or not.][/i]
Basically everything with zenphoto is done the lazy way, meaning when it is needed. See 2.

[i]5. If you change the "full size quality" parameter, you'll have to [fill-in-the-blank] to see the results.[/i]
See 2.

Best is just to try it..:-)

thanks for the answers! a few clarifications (before i can write it down for others):

re #2 above: is it correct that as soon as ONE user looks at an image and caches it, that image is cached in the system for ALL users (obviously, not cached in a new user's browser, but in the ZenPhoto system)?

re #3 above: ok. but if you *change* the quality settings then you would have to clear and reload the cache to see the effect of those changes on existing images, correct?

re #4 above: so... the "full image quality" parameter ONLY matters if a watermark is being added, correct? otherwise, it just used the image as uploaded. if this is true, it certainly makes sense to NOT upload huge images.

re: "Best is just to try it" - yes, i understand that is the viewpoint of some folks (programmer types especially). but here is my argument against that: does it make more sense for 10,000 new ZenPhoto users to figure something out by trial and error, or for somebody to just explain it well in the first place so that at least 9,900 of them don't have any problems. i'm not trying to be sassy, but rather just improve the community on a parameter that seems a bit... well... weak at the moment (no offense meant - the product rocks, no question about it).

re #2: Correct. The processed image is then to be found within the cache folder.

re #3: If you don't change the size setting, yes. You can clear the cache completly on the overview page or on each album edit page. (Or of course manually via ftp).

re #4: I would think so (actually I am not familiar with those parts of code). It never makes sense to upload huge images because probably our server could get problems for that. Please see our user guide for that.

re #5: [i](programmer types especially)[/i] Funny that you say that, I actually come from design not coding...:-)
Well, the community is not really weak, just the really active part maybe a little smaller than on other projects. We are also a small team which of course has its advantages.

If you really want to write a sort of manual that would be welcome.

thanks! very helpful.

for the record, i didn't mean that the community itself is weak! i just meant that the documentation of zenphoto seems to be lagging behind some of the other aspects.