Canon 28-135 IS 3.5 - 5.6
vs.
Sigma DC 18-125 3.5 - 5.6

A review of 2 great walk-around lenses for the Canon 10d

Review by Blaise Fiedler - do not copy or reproduce.

Test Settings

The pictures were taken with natural light. The Canon 10d was mounted on a tripod with mirror lock-up. For the Canon I disabled the IS, as recommended when using the lens on a tripod.
Aperture priority and CLOUD white balance (I did not want the Auto WB to kick in). Fine JPG, neutral settings.
All pictures taken within minutes of each other.

I tested perceived resolution / sharpness in the center of the image and on the far left. I also checked both lenses for purple fringing issues in the bottom right corner. See the 3 sections marked in red.

After pasting the cut sections in a document I resampled the whole document (bicubic) to double its size (+144% length and width). The sample of crops was then saved as a JPG with a "10" compression setting (max).

So what you're seeing in the samples is a closeup of actual pixels.

 

Part 1 - Canon vs Sigma at 28mm

28mm is the widest setting of the Canon 28-135 IS lens. The Sigma, despite having a maximum aperture of f3.5 drops its aperture fast - at around 20mm you're already forced to shoot at f4.0.

Center sharpness

Both zooms performed very well at 28mm. The Sigma DC 18-125 outperformed the Canon at the more extreme apertures - wide open and closed. At Canon's sweet spot of f5.6 the Canon had an edge and at f8 were both lenses were virtually equal.

View Center comparison crops

Edge sharpness

It's a different story on the edges. Wide open (up to f4) both lenses perform nearly identically. At f5.6 there is a surprising decrease of quality of the Sigma (it did trigger unanswered questions such as "Was there camera shake on the Sigma f5.6 sample?"). Between f5.6 and f11 the Canon 28-135 IS outperforms the Sigma 18-125 and at the extreme f22 both lenses are back on par.

The Canon 28-135 IS zoom really excelled on the edges. Open at f5.6 (its sweet spot at 28mm) it outperformed the Sigma DC 18-125 at all apertures.

View edge comparison crops

Purple Fringing

An incredible performance of the Sigma DC 18-125! The image is beautifully clean from from any purple fringing. See for yourself: at f4 it barely has any purple trace on the high reflective surface. The Canon see its purple fringing diminish as the aperture is closed but even at f22 is not as clean as the Sigma at f4. Congrats Sigma!

In terms of corner sharpness (the same pictures were used as above), the results are the same as above edge sharpness test. Both lenses on par at f4 and f22 and the Canon is sharper at f5.6 through f11.

View Purple Fringing and Corner Sharpness tests

Summary of 28mm comparison review

  f/
Sigma DC 18-125
Canon 28-135 IS
Center Sharpness 4
+
  5.6
+
  8
=
=
  11+
+
Edge Sharpness 4
=
=
  5.6
+
  8
+
  11
+
  22
=
=
Purple Fringing  
+

 

Part 2 - Canon vs Sigma at 125 mm

I simply moved the tripod back for this test so to have approximately the same frame. I had to guess the 125mm mark on the Canon 28-135IS and actually I was shooting on the Canon at 122mm rather than 125mm. I do not think this impacts the test results.

Center sharpness

What went wrong? The results are strange. Take a minute to look at the results of each lens before comparing them. The Sigma actually performed much worse at f8 and f11 than wide open (f5.6) or close (f22). Is this a normal finding?

Based on these tests Canon beats the Sigma all the way and particularly in the middle apertures.

View 125mm Center comparison crops

Edge sharpness

I am of course basing my conclusions on the same image set as above. The difference on the edge is much less noticeable than in the preivous example. Canon neverthess outperforms the Sigma accross the aperture range my a slight margin.

View 125 mm edge comparison crops

Purple fringing

Purple? Rather green! Was it the result of the white balance selection? Anyway the purple fringing virtually absent on the Sigma DC 18-125 at 28mm suddenly appeared to a small extent in a green color. It eventually was reduced as the aperture was closed but still remained on the Sigma.

Canon-wise there was also visible green fringing when the lens was wide open at 122mm. It had almost disappeared by f22.

View 125mm purple fringing crop shots

Summary of 125mm comparison review

So what happened to the Sigma here? It seems the good performance it held against the Canon at 28mm did not hold true at 125mm. Very soft in the center (I will actually need to retest this), softer than the Canon on the edges and some moderate green fringing. At 125mm there is no competition - the Canon outperformed the Sigma.

Part 3 - Canon 35mm 2.0 vs Canon 28-135 IS vs Sigma DC 18-125 vs Canon S50

How great are these fast primes? Is the 10d really worth the bulk compared with the cheap S50?

The 3 lenses were tested on the same scene at 35mm with the Canon 10d. For hte fun I also benchmarked these results against a consumer digicam, the Canon S50. The S50 was set on the tripod at exactly the same spot as the other lenses and I zoomed until it filled the whole frame.

Here is the first result - taken at f/4 for all lenses (Remember all screenshots at double the normal size)

Part 4 - How useful is the Image Stabilization?

A real life hand-held testing of the Canon 28-135IS vs the Sigma DC18-125.

Coming soon but don't hold your breath (after all you've got IS!)

 

All material (c) Blaise Fiedler 2004. Do not copy or reproduce.