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01-28-2009, 06:35 PM   #16
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QuoteOriginally posted by Alfisti Quote
TBH it's not that sharp an image. IMHO the 55-300 is sharper with much better colour and more contrast. The 18-250 has weak mid tones, I am always tempted to tweak the middle slider in levels.
That was taken at f/8, according to photozone this lens has 1850 lw/ph center resolution at 250mm. The 55-300mm has 1850 at 300mm and 1940 at 200mm so let's take an average and say 1900 lw/ph at 250mm for the 55-300mm.

That's quite a marginal improvement IMHO.

I agree it's not the sharpest image ever, but at 100%, I really doubt any consumer zooms will do significantly better to warrant the switch. Specially with the 18-250's all-in-one convenience.

01-28-2009, 06:41 PM   #17
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QuoteOriginally posted by Alfisti Quote
IMHO the 55-300 is sharper with much better colour and more contrast.
As an owner of both lenses, I agree 100%. Also the 55-300 is much longer (not just 50mm difference), has quick shift and doesn't creep. The only place the 18-250 wins is below 55mm.
01-28-2009, 07:29 PM   #18
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QuoteOriginally posted by kristoffon Quote
That was taken at f/8, according to photozone this lens has 1850 lw/ph center resolution at 250mm. The 55-300mm has 1850 at 300mm and 1940 at 200mm so let's take an average and say 1900 lw/ph at 250mm for the 55-300mm.

That's quite a marginal improvement IMHO.

I agree it's not the sharpest image ever, but at 100%, I really doubt any consumer zooms will do significantly better to warrant the switch. Specially with the 18-250's all-in-one convenience.
There is WAY more to it than Lw/ph, the 18-250 has no localised contrast. I have simply never, ever seen images like this from the 18-250

Snow Day... back to the zoo: Pentax SLR Talk Forum: Digital Photography Review
01-28-2009, 08:39 PM   #19
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QuoteOriginally posted by Alfisti Quote
the 55-300 is sharper with much better colour and more contrast. The 18-250 has weak mid tones, I am always tempted to tweak the middle slider in levels.
Well you have stated this three times now. Talk is cheap. I would like to see a comparison of the same image between both lenses showing that the 55-300 is indeed sharper with "much better color and more contrast." People make these kind of statements about lenses all the time, but I rarely see them back it up. Some of the statements remind me of the things people say when tasting wine. "It lacks limpidity and brightness." I'll bet it would be very hard to see the difference between those lenses. I already demonstrated that it is hard to see the difference between the DA* 50-135 and the 18-250 unless you go to 100% crop, and even then it is difficult.

QuoteOriginally posted by Alfisti Quote
There is WAY more to it than Lw/ph, the 18-250 has no localised contrast. I have simply never, ever seen images like this from the 18-250
Here are 50 good ones from the PPG. PENTAX Photo Gallery I don't find the 26 pics from the 55-300 any better overall. Certainly no noticeable sharpness difference. The point is that it is silly to argue about lens sharpness when the difference is almost imperceptible. "No localised contrast" is a red herring. Contrast and color are as subject to personal preference as is bokeh. The OP's original goal was sharpness.


Last edited by PentaxPoke; 01-28-2009 at 10:54 PM.
01-29-2009, 04:17 PM   #20
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QuoteOriginally posted by Alfisti Quote
There is WAY more to it than Lw/ph, the 18-250 has no localised contrast. I have simply never, ever seen images like this from the 18-250

Snow Day... back to the zoo: Pentax SLR Talk Forum: Digital Photography Review
Those images look pretty flat and uninspired to me. I'll keep my 18-250, thanks. I could post a few of mine that I think are better and we could go on with the ping pong game, but whatever.

Also, 300 isn't "much longer" than 250mm. The field of view is actually only 10% smaller (square root of the ratio of the focal lenghts.) It's hardly worthy of changing lenses IMHO.
01-29-2009, 06:14 PM   #21
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Flat? The level of detail in the cat is amazing. Adding extra brightness or contrast is easy, the rendering and the micro detail is beyond the 18-250.

The 250 is rarely 250. At about 15 feet the 55-300 will be something like twice as long as the effective reach of the 18-250 shrinks rapidly the closer you focus.
01-29-2009, 07:59 PM   #22
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QuoteOriginally posted by Alfisti Quote
There is WAY more to it than Lw/ph, the 18-250 has no localised contrast. I have simply never, ever seen images like this from the 18-250

Snow Day... back to the zoo: Pentax SLR Talk Forum: Digital Photography Review
Hm, proof is in the pudding, and I need to post pics, but I have plenty of zoo shots from my 18-250 that are in that ballpark. I know some are more picky than others, but I would be very very suprised if anyone could tell which images were taken with which lens.
01-29-2009, 09:43 PM   #23
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QuoteOriginally posted by Alfisti Quote
the rendering and the micro detail is beyond the 18-250.
Each new post seems to add another unsubstantiated claim. Now introduced into this discussion are new lens quality descriptors "rendering" and "micro detail" to the previous "localised contrast", "mid tones" and "colour". Although the OP originally was interested in sharpness, at this point I am intrigued to see a comparison from anyone, between these lenses (under the same conditions) to show just one, of any of these "measures of quality":

-Rendering
-Micro detail (presumably a redundant definition of sharpness)
-Localised contrast
-Mid tones
-Color

01-30-2009, 03:30 AM   #24
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Firstly, that is a super pic posted by PentaxPoke and it aptly demonstrates the capability of the 18 - 250.

There is a review of this lens in the Lens Review section and largely based on the very sharp pic in there I bought one.
I have not been disappointed with my purchase. That lens can produce sharp pics.

If anyone is basing their opinion on a handheld shot in poor light at the "far" end of it's range then that may not be a fair test.

Yesterday I read a review in the UK magazine Practical Photography of the 18 - 250 and the reviewer absolutely rubbished the lens.
I could not believe what I was reading. Whoever wrote that must have a hidden agenda.
01-30-2009, 06:11 AM   #25
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QuoteOriginally posted by kristoffon Quote
Also, 300 isn't "much longer" than 250mm. The field of view is actually only 10% smaller (square root of the ratio of the focal lenghts.)
I measured this. The 18-250 is an internal focus lens, and FOV increases for subject distances closer than infinity. For example at thirty feet (9m), the 18-250mm has the same FOV as the 55-300 at 200mm. At 9 feet, it looks like a 160mm lens.

Picasa Web Albums - Dan - FL compare

PS You can pixel peep the house shots and bird statues and see why we're saying the 55-300 shows more contrast. Sometimes it doesn't matter (e.g. the blue jay). Sometimes it does, because the photos look sharper and punchier.

Last edited by audiobomber; 01-30-2009 at 06:17 AM.
01-30-2009, 06:26 AM   #26
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Accoding to Pentax's lens specs, both the 55-300 and 18-250 have the same magnification, 0.28X, so your points about the lesser focal length on close focusing distances are effectively moot.

I took a look at your shots, audiobomber, and am yet to be convinced the 55-300 is any improvement on IQ over the 18-250. The color cast is easily fixed with white balance adjustment. Overall they look pretty much the same to me. EDIT: looking more carefully at the house and foliage shots the 18-250 seems to have retained more fine detail on the foliage on lower right corner. But I'm sure you'll point out a similar situation where the 55-300 does better.
01-30-2009, 06:28 AM   #27
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AB do you have both lenses? If so maybe you can runa few tests.

As for the FL, it's the samne magnification possibly because the 18-250 focuses closer but if shooting at the distances myself and AB have been talking about the effective FL is about half that of the 55-300.
01-30-2009, 09:00 AM   #28
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QuoteOriginally posted by PentaxPoke Quote
I already demonstrated that it is hard to see the difference between the DA* 50-135 and the 18-250 unless you go to 100% crop, and even then it is difficult.
Maybe to you. To me those 100% crops are hugely different.
01-30-2009, 09:01 AM   #29
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Dan,

I just don't see it. In fact, I think your shots make my point. Compare this one:
Picasa Web Albums - Dan - FL compare
With this one:
Picasa Web Albums - Dan - FL compare

There is no perceptible detail or sharpness difference. This in light of the fact that your shots put the 18-250 at a disadvantage. The shot taken with the 18-250 is at ISO 400 and f/6.3 the shot taken with the 55-300 is at ISO 320 and f/8. The higher ISO is a disadvantage because of noise, and the lower f stop of the 18-250 puts it at a sharpness disadvantage, yet the sharpness and detail difference is imperceptible. The 18-250 was wide open, and the 55-300 was stopped down a full stop!

Last edited by PentaxPoke; 01-30-2009 at 09:12 AM.
01-30-2009, 09:04 AM   #30
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QuoteOriginally posted by kristoffon Quote
Accoding to Pentax's lens specs, both the 55-300 and 18-250 have the same magnification, 0.28X, so your points about the lesser focal length on close focusing distances are effectively moot.
That's not the same thing at all. You're talking about close-focussing. I'm talking about someone trying to photograph a songbird that's 30 feet away. With the 18-250mm at full zoom, he effectively has a 200mm lens at F6.3. He would have the same FOV from the 55-300when it's set for 200mm, except the f-stop would be 4.5.
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