Just the face recognition of iPhoto on Mac OS X always made me envious eye on the competition. Accordingly, I was thrilled by the announcement that this with Picasa 3.5 photo also in administration from the Google home was feeding. You can now also use facial recognition offline 
There were facial recognition on the part of the Picasa Web Albums already since September 2008 , but who wants to unload all the images in Google's, recognize faces can be the only. In Namics.com there is also a little test to the Picasa Web Albums
Officially there is no Picasa 3.5 for Linux, so you have to make do by hand. Basically it is an installation in the home directory with a subsequent move to the system-wide / opt. A detailed guide to install Picasa 3.5 on Ubuntu can be found in OMG ubuntu.
Face detection and recognition
If you have specified in Picasa which folders to scan, they are processed and scanned for faces. First, these faces in the folder "unknown faces" are listed. This is a temporary folder that will disappear once you have assigned all marked as unknown faces or ignored. Here, the face detection is great, but sometimes even funny mistakes. Thus, for example, well recognized as a face. That faces on posters and paintings have been identified, however, is again a matter of opinion and more in the area of semantics classified. I found interesting was Picasa's ability to recognize faces over time again. I received a number a familiar face in infancy, in a different folder properly presented as a face infancy.
The unfamiliar faces can optionally be grouped into the same faces and then are quickly zuorndbar at a stroke of a person. This grouping works surprisingly well again. Overall, one can note also that the entire identification process takes place very fast. My several thousand images have been scanned in a few hours and thereby detected ~ 6000 faces.
As good as this group works so amazing is that actually familiar faces show up grouped as unknown. The re-identification can be so much to be desired. Picasa has problems, unfortunately, with twisted faces. From a certain angle they are no longer recognized. Purely logical point of view as no surprise, the inclusion of a rotation of the possible faces in a picture would also VER x times. Too bad it is nevertheless, that at least the stand on his head or a simple rotation by 90 degrees left or right has been incorporated in the recognition.
The surface
If you have completed the scanning process is generally followed by a mass post-processing. First, do the detected faces are assigned to other uninteresting and ignored. This is lacking in the consideration of a single image in a "All the faces ignore" button and you should ignore every single face. Especially with pictures from holidays, or even pictures of demos (;)) is an annoying issue.
I also noticed that while ignoring apparently is also a bug and ignored some faces appear again and again. At least in the overview. In the single image view they are then gone. On the setting when Folder Manager, so that the folder only to one or more scans, I could not, unfortunately, this error, as originally suspected, limit. And this error is above all in the series of faces and to have ignored an annoying problem. One starts at the first face, they must be considered in the frame to ignore rename or and goes with the cursor right to the next image, dip the pictures on which are found listed in the overview still unknown faces, again and again and you must comply always skip.
People mark hand
Picasa also offers the possibility to people in the image to highlight that it has not even recognized. For example, if the person with his back to the camera stand or as just mentioned, the face is turned. However, the end is here but also inconsistent and would be a revision and extension worth. The button to select a person immersed in principle as to where you would expect: In the single image view, right below the already marked faces. But this only if you take a look at specific album. If you are in unknown people album, then the knob is simply not available. Actually, to understand, as you while checking the detected faces so grade here is to highlight people and make it so sense at this time would also not found people to mark. Thus, one must first go through so the unknown faces and can mark in a second pass through the actual albums missing.
The subsequent selection of a person is properly resolved at first, but would tolerate a rework. It is obtained when clicking on the button a box in the photo, you can move to mark the person. However, the usually too big or too small, but rarely match and is therefore often not beat around the box in line with the size. Much defizile Clicking work.
Would be sent to give a simple as always changing cursor with which you will then simply the box around the person's face and after you release the mouse button, it would still great, the cursor would jump in the naming field. This would simply be losgetippt it and finished with Enter the designation.
After all, the cursor jumps to the current implementation, after the move and a simple click in the box in the name field. Not optimal, but usable.
Use of the name input field is also not consistent. You can jump in the person view with a double in the name field, you have to explicitly click in the album view in the name field. If you want to cancel the appointment, this is sometimes possible with ESC, which once again leaves an inconsistent impression.
In summary, Picasa should not pretend box in passenger mark, after marking, jumping into the name field, and select the name field in the album view allow double.
Moreover, it is very convenient that we can go back from an area with Zoom In ESC the complete photo and reach with another ESC, the album view. At this end you get used to fast and examined it again in other applications.
Once you are in the clustered unfamiliar faces, one can select a face with a tab in the Name field to jump below the image, type in the name and select Enter. When does a new person in the selection dialog with tab "New Person" mark and finish with Enter the entry. Designation as a mass by the well-thought sequence that is both mouse and keyboard users in no way 
Be careful in building a new person must be sure that the hook is turned off for the synchronization with the Web Albums, you do not want to give the profile photos of people at Google.
In contrast, the unknown faces overview without grouping is inconsistent: we have it from the point of no name input, but above the table. The jump is quite possible there with tab, so that the treatment goes well, even if the unnecessary bother changing view.
Something stupid is that you can jump out of unfamiliar faces overview by double-clicking a face to the photo in each album, this is the right person list is not possible. This lack of function is noted and sometimes the nerves a bit. In addition, the list also shows right deficits, as the auto-complete irregular in naming does not start when you enter a name and so is virtually impossible to use.
Desirable Features
Metadata
The pity is that the associated faces separately tagged in the albums people have, there are therefore no metadata about the faces in the image stored within the file, such as EXIF, IPTC and XMP. On the other hand, it would be the question of how to put the open as possible, so that others can use the program (in the future may Digikam). Was supposed to be quite open in their meaning according to Google's new motto. And the memory of 2 pixel coordinates and a name as a day would in my view a lot of sense.
Groups
In the current version of Picasa offers Unfortunately, no groups of people. Currently I have created ~ 350 people and this is a very confusing thing without groups. Something out this clear is the fact that the search may take place during the marking on the nickname that can be deposited as additional information for a person.
Face Zoom
There is no practical function in connection with the faces. This gives the possibility in the table, either the entire image or only the area to see, in which the face is detected. So a zoom function to the face. For the people albums in a short time an indispensable function to quickly find the image you want.
Negative Filter
Unfortunately, Picasa is missing a negative filtering. This has nothing to do specifically with the face recognition, but would immensely help all the faces to find the mark you want: a filter for images with no day / face. Currently, this makes it difficult to view only photos that have just selected any tags or no faces, mark, for example, tagging / People make up without the images already worked also be considered.
Desirable improvements
to be available to persons in zoomed images mark
If the can is marked by people already not optimal, so disturbing even noticed that you can tick in the zoom mode, no person. One must remember that is where the person was and then put in the 100% representation the appropriate box. Somewhat impractical.
Number of confirmatory images
Picasa will display a small orange icon next to the person, for which there are pictures to be confirmed. These entries in the lists of people come up, as is already the case if you use a calling people album and then scroll down (in this case the entry will open up and then scroll through the list below).
It would be a helpful to the information if you would get shown next to the orange question mark a number of how many faces are to be confirmed. Sometimes you may not be secure, and therefore open to a proposal without knowing the number so never know if there are new proposals.
Notice of the person proposed view
In person you can switch between all the albums and images to be confirmed. In principle, a clear function, it would be good if Picasa would remember if you want to see only the images to be confirmed, or at all. Currently you have to change in the people album again and again.
Faces automatically assign?
After a while I wondered whether Picasa should see the faces found not just automatically detect when a person has confirmed often enough. On the other hand, one can even display only the relevant faces and confirm all the "click and the false negative and then all confirm. The automatic sorting would probably involve more Korrigieraufwand and thus the less secure method.
Possible loss of face information in network drives
A gross error in Picasa I then stupidly also ran into. So we both can access the pictures, these are central to a file server. Now it is so that means time is crumbling, the network connection. If Picasa is running at the time, it has nothing to do better than the images to throw the jeweilligen drive from the database, it is necessary that a new scan. Unfortunately, I find the corresponding help entry grade in the Google did not help, but obviously some other problem and I hope it is fixed soon.
Conclusion
As you can see in some sections above, Picasa still suffers from many small children's diseases. These concern but fortunately only the surface. The face recognition works in themselves, in my opinion even better than I expected. If implemented, the proposals that I have mentioned in this article, I was very enthusiastic, so I see it but still positive, but notice that the marking of individuals is partly complicated than they should be.
