Road Train !!!!!!!!!!

by Russell McMahon

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I got the Canon EF-S 15-85mm IS USM this week after a lot of deliberation as an upgrade to my 18-55mm IS kit lens for my Canon 550D, and did some trial shots using it and found the images to be on the softer side, especially on the wide end even at f/8. I even tried manual focusing using the LCD screen to check whether there was a focusing issue, and toggling IS to see whether it made any difference.

My expectation from a lens upgrade were:

  1. Better image quality than the kit lens in terms of colours and sharpness, especially after having read that this was one of the best EF-S lenses in league with the Canon 17-55mm f/2.8 IS USM (this review with the sharpness comparison was one of the guiding factors for the potential)
  2. Faster & accurate focusing - the USM focus seems to be quite fast, but I have not yet had a chance to try the Servo mode which would throw better light on this
  3. Longer & wider - the 15mm end is definitely a lot wider than the 18mm of the kit lens, but the lens is also very soft at this end. The 85mm is also significantly longer and covers the ideal portrait range.

At the moment, the lens seems to be no better than the kit lens in terms of image quality sharpness. The wide end seems to be especially soft even when stopped down (reviews seemed to indicate that the mid range is the weak spot of this lens). The longer end seems decent, though not a great jump over the kit lens. So, effectively, points 2 & 3 seem to be served, but point 1 is a question mark.

I was wondering whether this is due to some defect in the lens or is this the expected output. I understand that zoom lenses in particular can have weaknesses at some focal lengths in their coverage, and also that there can be some quality issues, or just that my copy of the body and lens don't go well together. So, I would like to ascertain which case it is in order to make my decision.

Below are some 100% crops from the wide and telephoto end from the centre of the frame at f/8. I have also uploaded a series of shots at different focal lengths on flickr for details. Note that the images were shot using the Neutral picture style as high quality JPGs.

15mm 100% centre crop 15mm crop

85mm 100% centre crop 85mm crop

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possible duplicate of How can I test a new lens to make sure it is operating correctly? –  dpollitt Jun 23 '12 at 19:03
1  
Can you clarify what factors you are looking at in assessing "image quality"? Is sharpness your main concern? By the reviews, this should be a modest increase in that area over the kit lens, especially in the corners, but that's not really the main point of this lens. It's about a more versatile zoom range and image stabilization at a decent price. You shouldn't expect it to blow the kit lens out of the water in any area. –  mattdm Jun 26 '12 at 12:41
    
Well, I'm not sure if how well this is going to be answered short of having a different copy of the lens in the exact same picture. –  rfusca Jun 26 '12 at 14:29
    
Quite a lot of CA on the edges there, you may wish to shoot in RAW and use the DPP software to correct for lens specifics to remove that. Can make even the kit lens seem quite good –  Dreamager Jun 26 '12 at 14:30
2  
Considering these are 100% crops, I'd say, they are okay and acceptable. On a side note, don't view your images at 100%. –  fahad.hasan Jun 28 '12 at 10:51

3 Answers 3

up vote 4 down vote accepted

Ok, i went to pixel-peeper.com and did a search for your lens, here are some photos that you can use to compare to your own:

http://www.pixel-peeper.com/adv/?lens=13192&camera=1451&perpage=30&focal_min=none&focal_max=none&aperture_min=none&aperture_max=none&iso_min=none&iso_max=none&exp_min=none&exp_max=none&res=1

All these were taken with a 550D as you can see they are not really that sharp, I personally don't think your lens is that far off quality wise.

Now, here are some examples on a 7D:

http://www.pixel-peeper.com/adv/?lens=13192&camera=1335&perpage=30&focal_min=none&focal_max=none&aperture_min=none&aperture_max=none&iso_min=none&iso_max=none&exp_min=none&exp_max=none&res=1

As you see, there's not a big difference, the 550D has better quality maybe; I think your lens is just fine.

I hope this helps.

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1  
Thanks for the image samples, and the source. –  ab.aditya Jun 26 '12 at 17:01
    
Accepting this answer as it addresses my specific lens –  ab.aditya Jul 2 '12 at 8:34

I think there are a few things coming together to make your picture look a little soft. And while the 100% crop you showed isn't tack-sharp, I don't think a top-of-the-line lens at the same focal length would really perform much better if put to the same test (more accurately: if you compared the pictures from the two lenses side-by-side, you'd be able to tell which picture was taken with the more expensive lens. But if you looked at the expensive lens' picture in isolation, you'd probably still say that it was not sharp enough).

  • First of all, you're really far away. You're so far away that (in the 15mm example photo) people are only about 50 pixels high, and the letters on the sign are only about 15 pixels high. 15 pixels isn't a lot of room to make sharp letters anyway, but if you want sharp letters you'd need enough detail to be able to see the expression on the pedestrians' faces. In the 85mm example, where the letters on the sign are much sharper, I can almost make out the expression on the face of the person walking underneath it. When you zoom out to 15mm, you're trading sharpness (resolution) at any one point for a wider view of the scene.

  • It looks like there's a lot of moisture in the air. That means some haze, and since you're so far away from the subject, that means you're going to lose some sharpness.

  • There isn't a lot of contrast in the sign itself. You have good exposure for the photograph as a whole, but by looking at just the sharpness of the sign, you're getting a little misled because the sign is a little muted:

enter image description here

  • You used the Neutral picture style. That means your camera didn't do any sharpening at all. You should try sharpening the picture a little bit, and see if it looks better.

  • You're being really picky! (I am, too, when I look at my pictures. There's nothing wrong with that. But you have to know when to let it go.) When I expand the original (15mm) picture to fill my 15-inch widescreen-ish laptop screen, it looks nice and sharp across the entire picture. That's roughly the same size as an 8x12" print. Zooming in to get a 100% crop means zooming in about 4x. That would be a gigantic 32x48" (80x120cm) print! Unless you really need to print or view your pictures BIG, don't worry about how they look at 100%: you'd have to get your nose right up to the picture and really concentrate in order to see those defects.

So, how to improve your pictures:

  • Get closer! "Fill the frame" is common advice for a reason. Either get closer (preferably) or zoom way in (not as good as getting closer, since you'll be shooting through more atmosphere). If you still need the really wide view, you can try to take several pictures and combine them to get your panorama.

  • Sharpen your photos with post-processing. Either yourself, using software on your computer, or have your camera do it with a different picture style. Don't expect miracles, but it should look a little better.

enter image description here

  • Look at the picture as a whole, instead of zooming in to 100% to examine details. If you're heavily cropping your photos, you're probably using the wrong focal length. Get closer or zoom in more (or get a longer lens).

  • Remember to expose correctly. That means expose your test subject correctly. If your test subject is just a very small part of the overall frame, make sure that little bit is exposed correctly, and don't worry about the rest of the picture. This is different from when you're shooting in the field and you want the entire photo to have a correct, consistent exposure.

  • Choose subjects that play to the strengths of your lens. If straight lines and sharp angles (like letters on a sign) look a little fuzzy, take pictures of things that don't have straight lines and sharp angles. Nature photographs won't have straight lines in them, so if you're planning on using this lens to shoot waterfalls then be sure to use waterfalls for your test shots.

And one more thing: you said, I had read a lot about the sharpness of the lens on the wide end in the reviews, and it seemed odd to me that the longer end was sharper for me, but that's not what you were testing with your sample pictures. By standing in one spot and zooming in and out, you were testing the change in field of view as you zoomed your lens. If you really want to compare sharpness at 15mm to sharpness at 85mm, you need to make sure that your test subject is the same size on the sensor at each focal length. So:

  • take a quick look at this answer, then try to do the same thing with your lens. A car might make a good example: get up close to it, and "fill the frame" with the car at 15mm. Then zoom out to 30mm, and walk backwards until the car is the same size in your viewfinder, and take the next picture. Keep zooming out and walking backwards until you get your 85mm picture with the car the same size in the viewfinder as in the 15mm picture. Now it's okay to compare sharpness at different focal lengths, since each object in the frame (like a side-view mirror, or a handle, or a headlight) should be about the same size in pixels.
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Thanks for your analysis and tips. I will definitely keep it in mind when shooting. I used the Neutral style to see the default sharpness level, and have noticed some improvement when using the landscape\portrait styles. I agree that viewing at 100% is not the best thing to do - it was just that the trees in the background looked quite muddy. In addition, I had read a lot about the sharpness of the lens on the wide end in the reviews, and it seemed odd to me that the longer end was sharper for me. –  ab.aditya Jun 28 '12 at 11:57
    
Your point about haze might also be important in this case, as the monsoon rains have set in and the humidity levels are pretty high. –  ab.aditya Jun 28 '12 at 11:58
    
Awarding the bounty for the effort taken and feedback provided. –  ab.aditya Jul 2 '12 at 8:37

This is a general purpose zoom lens, not from the L-series which are well known for their sharpness quality. Even so the 15-85mm IS USM has a price tag aroung $700, it isn't the sharpest around.

Also bear in mind, each optical lens has its own, unique optical properties. A lens used for benchmarking, as stated previously, may not match yours. It can, and does happen, that you get faulty lens. In that case you should contact the vendor to seek a replacement.

I also found this comment from another buyer of this lens:

I purchased this lens along with a T2i body from B&H; expecting an upgrade in image quality from the EF-S 18-55mm. However, I needed to return one lens due to a very soft corner on the images. The replacement lens has uniform soft corners, so I can't say it was an improvement. Also, I'm encountering strong (almost neon looking) chromatic aberration at wide angles. Vignetting is slight due to the T2i correction setting. Overall, the images are soft (both lenses) and this is quite disappointing due to the price of the lens. The matching Canon ET-78E hood can cast a large shadow when using the built-in flash. Other owners seem to have success with the lens, but this has not been my experience. Lastly, Canon support stated that the EF-S 15-85mm is a "kit" lens and one should not expect sharp image quality. I could not believe that such a comment was made to a customer.

Some people might be lucky to get a good quality lens, other not as such. Once again, don't expect this kind of lens to be of the same class as the L-series.

My feeling on your lens, is that the picture quality/sharpness looks in par of the lens design.

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