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Chromatic aberration and the DMC-FZ18

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Real chromatic aberration -- Panasonic DMC-FZ5 and some optical stuff - by Tony Karp
Real chromatic aberration -- Panasonic DMC-FZ5 and some optical stuff
Virtual: Something that you think you have, but you don't.

Transparent: Something that you don't know you have, but you do.

Virtually transparent: Something...


My most recent post was about the Raw vs JPEG debate, detailing how the Panasonic DMC-FZ18's in-camera JPEG processing automatically fixes lens distortion. To demonstrate this, I posted a small example comparing the results in JPEG and Raw.

In a comment to the post, someone pointed out something that I hadn't noticed. The Raw version had some color fringing. It was absent in the JPEG version. Later that day, someone posted a picture from a DMC-FZ18 on one of the online forums, complaining about terrible color fringing they were getting from this camera, and sure enough, the picture was an extreme case of this problem. The poster then said that they hadn't seen this problem when shooting in JPEG format on this camera.

So I went back over the pictures I'd shot with my DMC-FZ18, about 2500 over the last month or so. Let's see... Tree branches against a bright sky? No fringing. My red barn with the white trim? No fringing. Other high-contrast subjects? No fringing.

With my Sony DSC-H2 and especially with my short-lived DSC-H9, color fringing was very common. But on my DMC-FZ18 pictures, all shot in JPEG, not a trace. Very interesting. Something else you were getting for free.

It appears that the in-camera JPEG processing in the Panasonic DMC-FZ18 is transparently cleaning up a lot of the common problems that plague digital cameras. Lens distortion is fixed. Color fringing is fixed. And I'll bet there are a number of lesser problems all being taken care of as well. And since these things are fixed transparently, people who shoot in JPEG format will never even know they existed. The people who shoot Raw, on the other hand, are in for some nasty surprises.

Now let's step back and take a closer look at Raw processing. According to the proponents of Raw shooting, their processing will give the user more choices and produce a superior image when compared to JPEG format.

A Raw format file contains, as the name implies, the raw data directly from the camera's sensor. If there are any problems with the behavior of the sensor, the lens, or how they work together, it's now up to you to fix them.

Although Raw shooters find all sorts of faults with in-camera processing, there's much to recommend it, especially the in-camera processing of the DMC-FZ18.

In designing the camera's processing, a lot of factors will be considered. For instance, suppose that testing in the design lab reveals that the lens has barrel distortion at its widest angle, which tapers off as the lens is zoomed. Or it's found that the lens-sensor combination produces color fringing that varies with exposure, focal length, and image contrast. Since all of this information is available at the time the picture is taken, it's easy to correct them in the camera.

What you'll be doing with Raw processing is trying to correct these faults, which will vary from picture to picture, by painstakingly tweaking your Raw processing software. In some cases, you may have to use several programs to fix all of the faults.

And the reward for all of this extra effort? The holy grail that you will eventually produce a better image than you could get straight from the camera. And up until now, that's been pretty much true, but the DMC-FZ18 changes the equation in the favor of JPEG.

Here's one example: I shoot lots of panoramas. I'll pop off anywhere from four to twenty shots and later stitch them together to produce something very long or very tall. All I have to do is drag my JPEGs into the panorama program and away we go. If the panorama doesn't work out, I can discard it with little time wasted.

What if I'm shooting Raw? First I have to locate the Raw files that will make up the panorama. Then I have to "develop" them while fixing the faults described above. Since I shoot most of my panoramas with the camera's lens at the widest angle, barrel distortion is a factor. Panorama programs don't like stitching pictures with barrel distortion, so this will have to be fixed. (The JPEGs from the FZ18 have produced some of the smoothest panoramas I've ever made.) Then the other faults must be adjusted and then the individual images tweaked, then saved in a form the panorama program can use. If there were ten JPEGs, the Raw equivalent will be at least thirty files. Okay, now let's stitch them together. Hmm...This one didn't work out. Too bad, and a lot of time wasted.

I've tried Raw processing on the three cameras I own that offer it, and each time came away puzzled, especially when trying Raw with the DMC-FZ18. I couldn't find any real benefit that justified the effort. Many of the promised benefits of Raw are theoretical and many may be holdovers from earlier cameras where Raw was necessary. With the DMC-FZ18, I was unable to produce a result from Raw that was strikingly better than what I could get from JPEG, certainly not worth the extra effort or the added complexity.

As I've said before, the Panasonic DMC-FZ18 may have shifted the Raw vs JPEG debate in favor of JPEG. The camera produces large JPEG files (very good), lets you turn off some of the in-camera processing (very good), and transparently fixes lens distortion, color fringing, and who knows what else (very, very good). The JPEG files that I'm getting from the DMC0-FZ18 are sharp, clear, with accurate color and exposure, easily tuned up in even the simplest of photo-editing programs.

So why, if all of this is true, does Panasonic offer Raw processing on the DMC-FZ18? I think the answer is that it's a marketing rather than a technical decision. There are a lot of people who will turn their noses up at a camera that doesn't offer Raw format. So marketing gave the customers what it thought they wanted. But the engineers at Panasonic went one step further. In providing superior JPEG quality, they gave the customers what they really needed.
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