I've just hit upon something rather cool and somewhat unexpected. Some of you will recall a column of mine from a year or so back called "JPEG...Seriously?" Well, I've found a reason for photographing JPEGs with my Olympus Pen E-P1. I can use them to get much, much better results at ISO 6400 than I could pull out of a RAW file using every trick I know.
(As usual, you can click on any of these illustrations to see them larger.)
Fig. 1. Olympus Pen RAW photographs at ISO 6400 are not lovely things. The full frame is on top, with a 100% magnification crop below. Observe the serious chroma noise, especially the horizontal and vertical stripes. © 2010 by Ctein.
As I wrote at the beginning of the year in "What Tests Don't Tell You," the E-P1 has some serious plaid chroma noise problems above ISO 800. It's great up to there, and then quality just falls off a cliff. ISO 1600 is marginal by my standards, everything above that is crap due to the chroma noise. Figure 1 shows a particularly egregious example of ISO 6400 quality in RAW mode; there's no way that I've found to make this RAW into a palatable photograph.
Now, take a look at the same photograph saved as JPEG in the camera (figure 2) . It's not perfect; there's some large low-frequency blotchiness, but that's the kind of stuff I could dodge or burn away. The chroma quality is not utterly sucking. It's usually not even this bad in most of the ISO 6400 photographs; this is just about the worst example I could come up with.
Fig. 2. The same photograph as in figure 1, but saved as a JPEG in camera. Excellent reduction of the chroma noise, but overall the picture is soft and veiled, and the highlights and shadows are blocked up. © 2010 by Ctein.
I'm truly amazed what the internal data massaging in the camera can do. If I had to, I could live with this as an okay snapshot. I don't much like that overall veiled quality, plus it's rather a shame losing several stops of highlight and shadow detail, most evident in the illuminated and dark stained glass windows and the trees).
So I said to myself, wait a minute...the Olympus can record in RAW+JPEG mode; what if I do that and then mix the two photographs in Photoshop? Start with the JPEG as the base layer, convert the RAW to a grayscale image (which almost completely eliminates the plaid problem), paste it in as a second layer over the JPEG, and set the blend mode to Luminosity (figure 3). I wind up with a photograph that has the clean chroma of the JPEG but retains most of the fine detail structure and tonal range of the RAW file. It's also a lot grainier.
So, I further said to myself, what if I use my most flexible noise reduction plug-in (Imagenomic NoiseWare) to get rid of majority of the grain in the RAW layer, but not so much that I'm seriously compromising fine detail? Which leads me to Figure 4. Hey, it works! It's grainy, but the grain is even and tight. It's a nice compromise mix of the best characteristics of both source photographs.
Fig. 4. This is not half bad! Chroma noise is much better controlled than in the RAW photograph, but it preserves most of the RAW's detail and tonal range. It also has an acceptable compromise between grain and fine detail. © 2010 by Ctein.
It prints out as a fairly decent 8x10 (Mike's seen prints and Oren and Carl have seen full-size JPEGs, so they can confirm this). Nothing I would call professional quality by my standards, but more than pretty enough. It would be even better if I did a little bit of dodging and burning in on the remaining blotches; I didn't because I'm trying to show what the file really looks like. But, it wouldn't take me long to clean it up a lot more.
Best of all is that I can turn at least 90% of this merging process into a Photoshop automation. Possibly all of it; I haven't experimented with enough photographs yet. Even by hand it's very fast, but an automation would save me a whole bunch of repetitive mouse clicks.
Here are some of the better ISO 6400 results I've gotten out of this new trick (figures 5–7). Is it perfection? Of course not. But seeing as I'd previously decided this camera wasn't any good above ISO 800 I'm a mighty happy camper.
Fig. 6. The merged RAW+JPEG photo combines most of the exposure range of the RAW file and most of the noise reduction of the JPEG. Compare the 100% sections at the bottom, RAW on left, RAW+JPEG on right. © 2010 by Ctein.
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Original contents copyright 2010 by Michael C. Johnston and/or the bylined author. All Rights Reserved.
"First, Olympus has access to much more proprietary information about the sensor and its specific hardware implementation than even, say, DxO does.
"Second, as Andrew Molitor says, the in-camera software (firmware) can be tuned to deal not only with a specific chip design/implementation, but a specific sample of a chip. This is really important because consumer devices, unlike scientific devices, have rather heterogeneous pixels.
"(Scientific devices are usually "grade 0," i.e., zero defects beyond a rather stringent specification. Moreover, scientific devices are generally CCDs, which are usually both more linear in response, and more homogeneous pixel-to-pixel than CMOS sensors. Because grade 0 devices are generally the cream of the crop, selected from much larger runs of devices, they also command very a very steep price premium. Your garden-variety D90 or E-PL1 is not going to contain a grade 0 sensor!)
"The sample-specific dark current calibration done at the factory accounts for variation not only between pixels, but between rows of pixels. On many cameras, this calibration is re-doable through the menus, useful since cosmic ray hits generate new hot and cold pixels over time.
"This sample-specific calibration information is potentially really important when making a zeroed image to start with, prior to application of conventional NR algorithms. This information is not stored in a RAW file, and thus is not available to any of the third-party RAW developers, fundamentally compromising their performance no matter how good they are (unless the dark subtraction is done upstream of the RAW file, which many forum idiots elsewhere deride as not kosher, but which is in fact a great idea, for reasons that now should be obvious)."