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dollyp Aug 16, 2005 7:40 AM

KM's 17-35 seems a bit expensive for such a short lens. Has anyone bought the Sigma 18-125? Is it a good alternative? What would be the drawbacks?


bernabeu Aug 16, 2005 11:41 PM

any zoom lens in excess of 2X is probably just a consumer grade 'junker'

you get what you pay for

Coolmax Aug 18, 2005 6:55 PM

The KM 28-75 is about 3x and is not consumer junk. I don't know where that idea came from. Bad advice.

dollyp Aug 24, 2005 3:18 AM

I'm trying to work out what is junk and what is not. In any case 28 at the wide end is not wide enough for a 'standard' zoom. I would have liked KM to have a lens covering around 18 to 50.

I'm asking what other lenses members of this forum have tried and what's good.

JimC Aug 24, 2005 7:47 AM

Lens quality is always subjective, and a lot depends on the conditions you're going to use one in.

Most lenses are not going to be as sharp wide open. But, stopped down to f/8, the differences between them tends to narrow.

Anytime you put that much zoom range into a lens (i.e., 18-125mm), you're going to compromise quality to some extent. But, it depends on how you're using a lens and what your expectations are. Many users think this Sigma is a good value for the range. It's not that bright (f/3.5-5.6), and it's not going to be as sharp as some other lenses, but it's small, light and relatively inexpensive.

Konica-Minolta also has a new18-70mm f/3.5-5.6 lens that is showing up with the Maxxum 5D (this is it's kit lens). This lens will also be sold separately ($149 in the U.S.). At this price, I wouldn't expect superb quality. ;-) But, it is probably going to be comparable to the inexpensive Canon kit lenses.

You can see the press release including this lens here:

Note that these new lenses are designed for Digital. They have a smaller image circle to make them smaller and lighter, so that can't be used on a 35mm SLR.

This also means that they won't work on any future "full frame" Digital SLR that KM introduces.

A good resource for evaluating lens sharpness is

Their lens grades are based on MTF tests (which are not subjective) versus user opinions (as in many other sites). But, many newer lenses are missing.

Also see the lens performance surveys (based on users opinions) at

Keep in mind that MTF tests alone don't tell you the whole story about a lens. So, look for opinions on things like Color, Contrast, Resistance to Flare, AF speed, etc. when comparing lenses. I'd also make sure to "test drive" some of the lenses you consider to see if you're comfortable with a lens' design.

JimC Aug 24, 2005 8:38 AM


FWIW, I decided on the Tamron SP 20-40mm f/2.7-3.5 lens for my wide zoom (discontinued now, but still available). This one would be equivalent to a 30-60mm lens on a 35mm camera (after a 1.5x crop factor). Most of my photos are taken in this focal range.

I have not used this lens yet on a DSLR, but I got a good report from 7D owner that has it. He's had multiple wide zooms and says this one is the sharpest wide open (and I plan on using it that way). It also rates higher than any other wide zoom available in Minolta mount at (and even tests better than the Minolta 20mm and 24mm f/2.8 primes). It's also a bit brighter than most wide zooms in this focal range (maintaining f/2.8 through 28mm, and only losing 1/2 stop to f/3.5 at 40mm). On the downside, it has a 6 blade aperture (if you care about that type of thing in a wide zoom).

User Surveys aren't as flattering for things like flare resistance with this lens. But, I'll see how it works on a KM DSLR when I get one (I don't own a KM DSLR yet).

bernabeu Aug 24, 2005 7:07 PM

as i stated before:

2x is the max range for a QUALITY zoom lens

JimC Aug 24, 2005 7:58 PM

bernabeu wrote:

as i stated before:

2x is the max range for a QUALITY zoom lens

Well, I don't think you can make a blanket statement that 2x is the max, if you want it to apply to any lens in any focal range. Quality is subjective, too.

Some of the highest rated zoom lenses are greater than 2x zooms. Look at the MTF Tests for the Minolta 80-200mm f/2.8G, Canon 70-200mm f/2.8L, Canon 70-200mm f/4L, Sigma 70-200mm f/2.8 EX as examples.

Or, try this 28-85mm f/3.3-4 (3x). It tests better than any zoom made by Minolta:

It's probably more challenging to make a zoom with a longer range with high quality, but it can be done. I doubt optical engineering technology is standing still either.

How you define quality is another matter. Are you looking at resolving power alone, is barrel and pincushion distortion a big consideration, resistance to flare, are you using it in better light at smaller apertures, or do you need to use it wide open. Any lens is going to be a compromise to some extent (size, weight cost, flexbility, etc.).

So, a user will need to decide for themselves what's more important.

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