Previous page Next page

Resolution Chart Comparison (JPEG and Raw)

Images on this page are of our standard resolution chart which provides for measurement of resolution up to 4000 LPH (Lines Per Picture Height). A value of 20 equates to 2000 lines per picture height. For each camera we use the relevant prime lens (the same one we use for all the other tests in a particular review). The chart is shot at a full range of apertures and the sharpest image selected. Studio light, cameras set to aperture priority (optimum aperture selected), image parameters default. Exposure compensation set to deliver approximately 80% luminance in the white areas.

What we want to show here is how well the camera is able to resolve the detail in our standard test chart compared to the theoretical maximum resolution of the sensor, which for the charts we shoot is easy to work out - it's simply the number of vertical pixels (the chart shows the number of single lines per picture height, the theoretical limit is 1 line per pixel). Beyond this limit (which when talking about line pairs is usually referred to as the Nyquist frequency) the sensor cannot faithfully record image detail and aliasing occurs.

This limit is rarely attained, because the majority of sensors are fitted with anti-aliasing filters. Anti-aliasing filters are designed to reduce unpleasant moiré effects, but in doing so, they also reduce resolution (the relative strength and quality of these filters varies from camera to camera). In theory though, a sensor without an AA filter - such as the Foveon X3 sensor in the SD1 - can deliver resolution equal to its Nyquist limit when coupled with a 'perfect' lens. Therefore, even though it may be near-unattainable in normal shooting situations, an understanding of a sensor's theoretical limit provides a useful benchmark for best possible performance. Nyquist is indicated in these crops with a red line.

On this page we're looking at both JPEG and Raw resolution. For the latter we've used Sigma Photo Pro for conversion with sharpening set to a minimum, followed by unsharp mask in Photoshop:

  • Load Raw file into Sigma Photo Pro
  • Set Sharpness to -2 (all other settings default)
  • Open file to Photoshop
  • Apply a Unsharp mask tuned to the camera, here 150%, Radius 0.3, Threshold 0
  • Save as a TIFF (for cropping) and as a JPEG quality 11 for download
JPEG (4704 x 3136) 5.73MB Raw (4704 x 3136) 3.67MB

Vertical resolution


Horizontal resolution


The crops above show that, freed from the blurring effect of an anti-aliasing filter, the SD1's Foveon X3 sensor resolves extremely highly in this test. It's capable of distinguishing the lines on our resolution chart right up to its Nyquist frequency, and continues to render line structure some way beyond. This 'false' detail is the flipside to the lack of an anti-aliasing filter, and while purists may object that it's not an accurate reflection of the scene, it does tend to help make real-world images look more detailed. Notably there's not even a hint of colour moiré, because the X3 sensor records full-colour information at every pixel location.

Compared to its APS-C competitors, the SD1 outresolves Bayer-sensor cameras with similar or slightly-higher output pixel counts such as the 16.3MP Pentax K-5 or 18MP Canon EOS 7D. But compared to the 24MP Sony Alpha SLT-A77, things are much closer, although as we'd expect the Bayer-sensor camera shows more colour artefacts.

Previous page Next page
I own it
I want it
I had it
Discuss in the forums


Total comments: 9

To update a three and a half year old review a little, as a recent convert to the Foveon sensor in this Sigma (albeit in the DP2 Merrill iteration) I can testify that the latest Sigma Raw processing software, Photopro 6.3, which is used for the SD1 Merrill as well ithe DP2, does not leave much to be desired, at least to a relative newcomer to Raw processing. And this running on Windows 7 on an ancient Core 2 Duo at 2.66Ghz with 4 Gb of memory. There may be frustrations for those who wish to devote more time to arcane debate than taking shots, but on the whole Photpro6.3 hits the spot. Hats off to Sigma....


Is this the 24-70 ART lens that you are using ? I have the 28-80 HF and 18-50DC's but the Chromatic Aberration is shocking with these and I cannot achieve a constant colour, without discoloration around the edges. I was thinking of buying an adapter and looking for a better lens, possibly a Nikon one.


Use a full frame lens like the 24-70 F2.8 EX DG HSM. You will get fantastic results. Use it properly - on a tripod at 100 ISO and F8. Have good light. Shoot raw. Convert to 48bit tiff. Edit with the appropriate skill. If the results don't blow you away, your doing something wrong.


I photograph textiles for a living and I have a love hate relationship with this camera. Some of the results are stunning, then at other times it is infuriating. The fact that I cannot Wifi the camera drives me mad,a friend is trying to solder up a device, so I can attach a ribbon cable to compact flash type 1 holder, then have a type 2 WIFI one mounted externally. I am envious of my colleague that works with a Nikon and uses her iPad to control and tether her camera, with an instant review of the post and final image .


If you shoot at 400ISO or less, use the best lenses, shoot raw and use the latest version of the much improved Sigma raw conversion software, you will be able to upsize your clean artifact free files to around 6700 pixels across giving you an equivilant resolution of a 30MP Bayer sensor. I do this all the time and the results are fantastic. Using a full frame lens on this sensor gives you images that are sharp to the corners and almost distortion free. The 24-70mm F2.8 HSM on this sensor enables image quality way beyond anything I ever shot on a 5D2 or 5D3 with L lenses.. When you get to know the tool and develop skill to use it well, the results will blow you away. Most people want it easier than that. You reap what you sew!

1 upvote

I purchased an SD1 for my business of photographing textiles in a studio situation and I feel totally deflated. The actual image quality is excellent, but the tethering capabilities are pathetic. I expected to be able to click from my PC to launch a shot, then instantly see what I had taken, before moving on to the next item, which sadly is not the case. Their software application known as Sigma Capture Pro should be reported to the trading standards council, as there is nothing 'Pro' about it as it is just a glorified remote shutter release program. Furthermore in order to have access to your images on a PC, you need to go into the menu function on the camera and disable the 'remote capture program' then select mass storage to view your images. Going through this process with every shot, may be good for you cardiovascular system, but for someone who relies on seamless throughput to make a living, this camera is junk.


Tethering capabilities? lol. You are more interested in showing off in front of clients than achieving great results. Re-align your priorities. You do realize that 90% of the time the images are used at 400 pixels wide on a web site - do you? you don't need to check each shot at 100% mag on a full size screen before you know you got it. Give us a break with your grandstanding.


I was looking at the photo comparison today, comparing the SD1 against the new Canon 5 D Mk III, the Nikon D800E, and the Pentax 645 D . . . at ISO 800 . . . and I just can not believe my eyes. Take a look at this:

The SD1 never ceases to amaze me.

Scott Greiff

Why won't the comparisons load?

Total comments: 9