DP1 Shootout Pt. 4a - High ISO Performance in Low, Incandescent Light

The technology behind the Foveon sensor at the heart of the DP1 has been well covered elsewhere. One interesting aspect of the three-layered Foveon design is that the quality of color representation in low light is partially dependent on the spectrum of light available. For example, low light provided by natural light (i.e., sunlight through a window) will typically produce better colors than will a similar level of light coming from an incandescent source. I decided to do this first high ISO comparison as a sort of "worst case" demonstration. Here I will show crops from the Sigma DP1, Fujifilm F31, Canon 5D with 28mm f/2.8, and Olympus E-420 with 14-42mm f/3.5-5.6 lens. The photo compared was taken in low light, indoors, with an incandescent light source.

The competitors:

The Sigma was shot at f/5.6, Fuji at f/4, Canon at f/11, and Olympus at f/5.6. Shutter speeds were manually determined to match exposures. For detailed EXIF information, please consult the files available for download at the end of this post. A sturdy tripod was used in all cases. The subject distance was altered for the F31 shot in order to keep the field of view consistent.

An important thing to note is that the crops are grouped by ISO, which may not be relevant to actual practice. For example, the Fuji F31 has a one stop advantage in maximal lens speed compared with the DP1 (f/2.8 vs f/4). Therefore, one might compare the ISO 800 F31 crops with the ISO 1600 equivalent (ISO 800 pushed one stop) DP1 crops. Likewise, the Canon lens has a one stop advantage over the DP1; thus one might want to compared the ISO 400 DP1 crop to an ISO 200 5D crop. However, using the Canon lens at f/2.8 will result in a more shallow DOF than will using the DP1 at f/4. Therefore one might choose to shoot the Canon at f/6.3-7.1 for acceptable DOF in a situation where f/4 would do with the DP1. In such a case, the more relevant comparison would be DP1 ISO 400 to Canon ISO 1000 or 1250. I will simply present the crops according to ISO and leave it to you to decide which ones should be compared.

All images were resized using Photoshop Bicubic Sharper to match the diagonal pixel dimension of the native DP1 files. Therefore, the DP1 crops are at 100% of the original, and the 5D/E-420/F31 crops have been downsized as needed. All were shot RAW and processed using the settings specified in the introduction. The exception was the Fuji, which does not offer RAW. Although I custom white balanced all cameras at the time of use, all required further adjustment during RAW conversion to get a closer white balance match. I also applied a 25% cooling filter in Photoshop.

Here is the overall test scene with the specific regions examined identified in the yellow boxes:

ISO 400 Crop 1:

ISO 400 Crop 2:

ISO 400 Crop 3:

ISO 400 Crop 4:

ISO 800 Crop 1:

ISO 800 Crop 2:

ISO 800 Crop 3:

ISO 800 Crop 4:

ISO 1600 Crop 1:

ISO 1600 Crop 2:

ISO 1600 Crop 3:

ISO 1600 Crop 4:

I think these crops speak for themselves. With this quantity and spectrum of lighting, the DP1 high ISO color fidelity is poor. Boosting saturation in SPP (not shown) can help restore some punch, but it does not restore color accuracy. Nor does the use of custom WB use at the time of the shot help in any way that I could discern. On the positive side, high ISO DP1 files are clean, so black and white conversions can produce high quality results. The degree to which they are noise free raises the question as to whether SPP is applying some mandatory noise reduction. I look forward to trying 3rd party RAW processing applications as they become available and hope to read some analysis of the RAW files by those with expertise in that area.

What about the little Fuji? I think it can stand proud after this comparison. Sure there's some mandatory noise reduction going on with the F31, and yes it shows the least usable detail in this group. In my opinion, the good color fidelity of the F31 translates to better overall image quality than the Sigma DP1 for color, high ISO, small prints in this type of lighting. Especially so considering the one stop advantage of the Fuji lens (f/2.8 vs f/4), i.e. comparing F31 ISO 400 vs DP1 ISO 800 or F31 ISO 800 vs DP1 ISO 1600 (equivalent).

I realize that this comparison gives a somewhat different impression than the preliminary one I shared in the discussion area. Comments and suggestions are, as always, appreciated.

Special thanks to Serhan for lending me the Fuji F31 used in this test. In Part 4b of the shootout, I'll show the results from a similar comparison conducted in mixed low light.

Posted by Amin


Anonymous said... April 25, 2008 at 10:47 PM  

It looks as if the noise reduction method employed by the Sigma is different from other manufacturers in that they keep the sharpness but wash out the colors.

Kind of like using bright soft white lighting on old people on TV to make their wrinkles disappear.

Anonymous said... April 26, 2008 at 6:48 AM  

What about low ISO color shift for such conditions?

amin said... April 26, 2008 at 8:14 AM  

anonymous #1 - Yes, it does look that way. Maybe there's not much luminance noise to begin, but they end up doing a lot of color NR??

anonymous #2 - I'll post an example for you, hopefully later today.

Thanks you both for your comments.

ΒΑΣΙΛΗΣ ΓΙΑΝΝΑΚΟΠΟΥΛΟΣ said... April 26, 2008 at 7:21 PM  

Hi, I did a similar comparison over at http://vasyan.blogspot.com/2008/03/iso.html, between the e-510 and the F31fd. Its in Greek but pictures speak for themselves... Anyway, I reached a similar conclusion as regards the performance of the little Fuji. Not too shabby eh?

amin said... April 27, 2008 at 12:45 PM  

Vasilis, thanks for looking and sharing your comparison. Yes, the Fuji continues to impress. Regards, Amin

Amin said... May 13, 2008 at 9:08 PM  
This comment has been removed by the author.
Amin said... May 13, 2008 at 9:12 PM  

"What about low ISO color shift for such conditions?"

There is still quite a bit of desaturation and some shift as well at ISO 100 in such conditions. Click here for an example.

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