18-55mm and 55-250mm kit lens SWEET SPOTS

Started Aug 19, 2010 | Discussions thread
Mjollnir
Regular MemberPosts: 380
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Re: 18-55mm and 55-250mm kit lens SWEET SPOTS
In reply to Mlots, Aug 20, 2010

I have both these lenses and can tell you the sweep spot for the 18-55 IS is 35mm at f/5.6. It's also very sharp at 18mm at f/3.5, though there's fairly noticeable distortion depending on what you're shooting. If you shoot in RAW, this can be corrected very well in DPP.

But distortion correction softens the picture slightly (even in DPP), so if you want the absolute sharpest images possible then shoot in RAW, don't use the rotation or distortion correction tools, and otherwise use the sharpness, brightness/contrast/colour, noise reduction and all the other lens correction tools to get the best out of your images.

The 18-55 IS is pretty sharp for a kit lens, so you don't lose a great deal out of using the DPP lens distortion correction and rotation tools. I usually compensate for them by bumping the sharpness up 1 point, though this can make the noise more obvious in low light shots.

The 18-55 IS is at its worse at 55mm, no matter what F-number you use. It's still good enough for a kit lens though, and has no noticeable lens distortion.

For the 55-250, the sweet spot is 135mm at f/8. I've found macro-style shots at 250mm at f/5.6 are pretty dull and lack too much detail. Stopping down to f/8 gives great results for a lens at this price. I also find that DPP generally does a much better job of correcting chromatic aberrations and colour blur in RAW shots taken through the 18-55 IS than the 55-250. Sometimes, it seems very obvious where the blue/red lines are on high contrasting areas but DPP just doesn't seen to want to fix them, whereas on the 18-55 IS it fixes them almost all of the time, at least on sharp shots.

Lens distortion is much less on the 55-250, with the worst being a bit of pincushion at 55mm. But it's subtle enough throughout the range for me to never use DPP to correct it. I'd rather preserve the sharpness of the original image and just let DPP fix the vignetting and (if it can manage it), any chromatic aberrations.

I've never got around to comparing 55mm shots on both lenses, but given that 55mm is the bad spot for the 18-55 IS, I'd guess that the 55-250 is sharper with the trade-off being a slight lens distortion.

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