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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. 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, when coupled with a 'perfect' lens, will deliver resolution equal to its Nyquist limit. Therefore, even though it may be effectively unattainable with normal equipment 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 a (more) level playing field we convert the latter using Adobe Camera Raw. Because Adobe Camera Raw applies different levels of sharpening to different cameras (this confirmed) we use the following workflow for these conversions:

  • Load RAW file into Adobe Camera RAW (Auto mode disabled)
  • Set Sharpness to 0 (all other settings default)
  • Open file to Photoshop
  • Apply a Unsharp mask tuned to the camera, usually 100%, Radius 0.6, Threshold 0
  • Save as a TIFF (for cropping) and as a JPEG quality 11 for download
JPEG (4000 x 3000) 3.3MB RAW (4000 x 3000) 2.9MB

Vertical resolution

JPEG
RAW

Horizontal resolution

JPEG RAW

The Canon Powershot G15 does well in our resolution tests, resolving all nine lines accurately up to around 2250 LPH in the camera's JPEG mode. Converting your RAW files gives you some additional detail, resolving the chart up to around 2400 LPH with some 'false detail' beyond that. This is getting pretty close to the Nyquist limit, which is equal to the G15's vertical output pixel count - i.e. 3000 pixels/LPH.

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Comments

Total comments: 3
karlowac
By karlowac (3 weeks ago)

I got myself one of these 3 months ago at a store sale. They were making room for G16 so the price was lowered to less than EUR300 (a bargain, compared to G16's EUR430). I had thrashed my old Canon P&S just two days prior so I was in the market for an inexpensive replacement (read EUR100 to EUR200 tops).
All I can say is: I payed a little bit more but got more than I ever expected.
It is an incredible little camera, I fell in love with it.
It is compact but beats my Canon 500D in some areas.
With quality lighting in place I can barely tell the IQ difference between those two physically totally different cameras.
I can't imagine anyone ending up disappointed with this little gem.

0 upvotes
Matte Steven
By Matte Steven (5 months ago)

Have to say, G15 is a classic DC in last years.

0 upvotes
Gary R.
By Gary R. (10 months ago)

It's an interesting list of "cons" here. I've had cameras with articulating screens, and found I really didn't use them all that often, so really don't consider it much of an issue either way. "No automated panorama mode", again, is a plus to me. The stitch-assist features are very useful for producing high resolution panoramas with user control if things don't stitch perfectly the first time (where the 'auto' ones fail so often, I feel they belong on camera phones and low end point and shoots, not on enthusiast models...I really hate having only that automated option, forcing me to use manual settings, on my LX7).

I will often set my max. auto ISO to 1600 anyway, so that "con" really isn't much of one, and the HDR issue is of no concern for me.

So all in all, this is a very impressive list of 'cons'. If these are the worst faults of the camera, it sounds like Canon has done a very good job.

0 upvotes
Total comments: 3