Introduction

I’m presenting images from three cameras: the Sigma SD14, the Canon Rebel XTi (aka Canon EOS 400D), and the Sigma SD9. Full size JPGs and raw files are available for each photo. The purpose of this web page is to provide images to help compare image quality, but not to provide a full review of the cameras. The primary difference between the cameras is the sensors they use. The Sigmas use a Foveon sensor, while the Canon uses a traditional Bayer sensor.

Conditions

I tried to provide a fair comparison by holding conditions as constant as possible. The cameras were set on full manual mode. Light levels were measured with a Sekonic L-308B light meter. Aperture, shutter speed, white balance, and ISO were set the same for all three cameras within each set of photos. The photos were taken with 50mm prime lenses, the Sigmas with the Sigma 50mm f/2.8 EX Macro and the Canon with the Canon EF 50mm f/1.8 II. The JPGs were developed using Iridient Raw Developer and Adobe Lightroom, as labeled below, on a monitor that is calibrated with ColorEyes software to a color temperature of D50 and L* gamma.

Unfortunately there were some issues which prevent a completely fair comparison. There was an extensive discussion on the shortcomings of this comparison at the DP Review Sigma forum. Unfortunately, I sold the Canon already so I can't retake the photos.

• The Sigma lens is their top-of-the-line model ($270 new) while the Canon lens is their bottom-of-the-line model ($75 new).
• I’m not providing a very wide range of photograps. Two of the four sets are of faces because I’m most interested in photos of people (and specifically the people shown below).
• The chip chart photos were underexposed by about a stop and a half.
• Several of the pictures were soft, either from focus or motion blur, so these photos don't allow you to compare resolution. More on this issue in the discussion section below.

Images

Face, Quartz Halogen Lighting

• Light Source: Lowel DP light with quartz halogen bulb bounced off white foamcore board.
• Camera white balance: Incandescent
• Aperture: 4.0
• Speed: 1/60 sec
• ISO: 200
• Developer for JPGs: Iridient Raw Developer
• Unfortunately the highlights were blown out. (The light was too close because I was trying to keep the ISO as low as possible.) Next time with a softbox.

Face, Sunlight

• Light Source: Sunlight through clouds coming through a window.
• Camera white balance: clouds
• Aperture: 2.8
• Speed: 1/60 sec
• ISO: 100
• Developer for JPGs: Iridient Raw Developer
• I put up an extra photo with the Canon just because I liked it.

Outdoor

• Light Source: Winter morning light
• Camera white balance: Sunlight
• Aperture: 4.0
• Speed: 1/320 sec for Sigmas, 1/250 sec for Canon (closest possible setting)
• ISO: 100
• Developer for JPGs: Adobe Lightroom

GretagMacbeth ColorChecker chip chart

• Light Source: tungsten
• Camera white balance: incandescent
• Aperture: 2.8
• Speed: 1/8 sec
• ISO: 100
• As noted above, all the photos were underexposed by about 1.5 stops. Two sets of JPGs are posted, one developed with Raw Developer and the other with Lightroom. Below the photographs are two more jpgs with more accurate representations of the chip chart colors for comparison. The one on the bottom right is from the authors of “Real World Color Management.”

Discussion

To my eye:

The Sigmas give a more pleasing image than the Canon. The colors appear richer and deeper. (The difference is not just saturation level; increasing the saturation level of the Canon images does not result in the same color quality as that of the Sigmas.)

The Sigma images appear to be more “present” and 3-dimensional. The Canon images tend to look flattened, while subjects in the Sigma images seem to actually be there. Some people talk about the “Foveon pop,” which is related to this. Mike Chaney, maker of Qimage uprezzing and printing software, has a good discussion on the reasons behind this.

The Sigma images capture more skin detail.

I didn’t see much difference between the SD14 and the Canon in the outdoor shot, especially looking at the green trim. I think this is because the Bayer sensor of the Canon has twice as many green photo-sites as red ones, so it should do a better job at capturing green than other colors. Since the Sigmas have an equal number of green, red, and blue photo-sites, they should do better with skin tones, where there is crucial information in the red channel.

I was surprised by how inaccurately all three cameras rendered the GretagMacbeth chip chart, although it might be my fault for underexposing the images. You can see the differences between the images from the cameras and from the scan (which is quite accurate to my eyes). I was not able to bring out the orange (chip on far left, second down) with Raw Developer, but I was able to get it by tweaking the orange saturation, hue, and luminance in Lightroom. Raw Developer would be stronger software with similar controls over individual colors. I was also surprised at the cameras’ poor representations of the “light skin” chip (second from left, top row).

Even though all of the face shots are soft, it looks to me like the three Canon photos of faces are less sharp than the Sigma images. Some possible reasons for the Canon images to be softer:

• More motion blur. It's a a lighter camera, with less inertia to resist my apparently shaky hands. I don't see blurriness in the outdoor shot, which had a faster shutter speed.
• Lower quality lens, but this is unlikely.
• By coincidence the kids happened to move out of the shallow focal plane for these images but not the others, but I don't think this is very likely.
• Problem with autofocus on the Canon I was using? ( I used autofocus on all of the images in the test.) The Canon autofocus was set to use the center point only and I focused on the subject's eye for each photo. Clearly the focus is too far back on the Canon incandescent shot of my son. It might be interesting to note that I got better photos from the SD14, which I'd had for only a week or two at the time of the test, than with the Canon, which I'd been using heavily for over half a year.

Those are my thoughts. I posted the RAW files so you can judge for yourself.

Although there were problems with the test, for me it was actually a success, overall. I took a fly on investing some money in switching from the Rebel XTi to the SD14 (after having the Rebel XTi for only half a year) based on photos I had gotten from the SD9 and photos from the SD14 I saw on the internet (especially Carl Rytterfalk's). After using the SD14 for a little while, I felt its higher image quality overcame the drawbacks of switching (cash outlay, worse low light capability which decreases photo opportunities for me, and slower in-camera write time which slows me down in reviewing images after shooting). I'm very pleased with the sharpness I usually get with the SD14 especially in skin details, the 3-D quality of the images which give the subject more "presence" to my eye, and the richer colors. Although the blurriness of the photos I posted make the comparison less than ideal, I think they still show the qualities that I like in the SD14.

My Story

I’ve been taking photos for almost 30 years, but I started getting serious about it (as a hobby) about 4 years ago, primarily to capture my children as they grow (and secondarily to improve my videography skills, which I do professionally). In 2004, I bought my first digital SLR, the Sigma SD9, because I liked the images I saw from it on PBase, especially those of Carl Rytterfalk. After a couple of years, I found myself taking many fewer pictures with it because I was frustrated with the SD9’s lack of low-light ability (it’s essentially an ISO 100 camera) and the slow workflow (I processed each photo through Sigma Photo Pro and Adobe Photoshop.) Due to this frustration, I bought the Canon Rebel XTi and Adobe Lightroom in early 2007. I loved getting photos in any light and the zippy workflow, but when I zoomed in on the images I was disappointed with the quality; at 100% zoom the images seemed less solid, with a shimmering quality and “shallower” colors compared with the SD9 images. In late 2007, I decided to take advantage of the relatively low price of the SD14 (I bought it for $850 compared with the initial $2500 MSRP) and to sell the Canon on eBay. I’ve been quite happy with the SD14 image quality and feel that it more than makes up for the deficits compared with the Canon, such as greater noise in low light (although the SD14 is a huge improvement over the SD9) and a much slower file write time from the buffer. Continuing to work with Lightroom has eliminated the slow workflow issue I had with the SD9.

If you’re interested ing seeing some of my photos, take a look at my favorite candids, portraits, and landscapes. If you’d like to see what the SD14 can really do, take a look at Carl Rytterfalk’s website and sample images on PBase. If you want to learn more about the SD14, check out Sigma’s website and the Sigma forum at DP Review.

If you have any questions or comments, please contact me at 2006@snarton.com.