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01-30-2009, 09:13 AM   #31
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QuoteOriginally posted by dougiewill Quote
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.
If you're referring to my house shot, that was not handheld, it was on a tripod with 2s lockup.

I don't want to be construed as an enemy of the 18-250. I have one, I've never regretted buying it and I intend to keep it. But I choose it over my 16-45 + 55-300 for convenience, not IQ. The 18-250 has serious distortion at 18mm and no way it's as sharp as either. I have done two different types of resolution tests vs the 55-300mm, long distance and a cereal box. IME the 55-300 has greater resolution and nicer colours. It definitely has significantly greater range. I don't care if any of you believe me or agree with me, I'm just stating what I've found with my copies of these lens.


Last edited by audiobomber; 01-30-2009 at 09:29 AM.
01-30-2009, 09:38 AM   #32
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QuoteOriginally posted by PentaxPoke Quote
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!
My apologies, these tests were initially intended to show FOV. They are not comparable for anything else, in fact now that I look at the IXIF data, they were taken at the same time but with different cameras. I guess I'll have to show a resolution test now, but February is an impossible month. Let's call the resolution issue undetermined. (BTW, this was not the test that caused me to say the 55-300 is sharper)
01-30-2009, 11:05 AM   #33
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QuoteOriginally posted by audiobomber Quote
My apologies, these tests were initially intended to show FOV. They are not comparable for anything else, in fact now that I look at the IXIF data, they were taken at the same time but with different cameras.
Ah. That explains the fairly obvious difference in contrast/rendering, then.

BTW, for the OP, I think these discussions have demonstrated exactly what they should: going from one of these zooms to another will results in difference that some say are obvious and others can't see at all no matter how hard they try. I would conclude from that: the differences are real but won't be noticeable to a lot of people. You'll have to look at a bunch of samples to decide for yourself whether you'll be one of those who sees obvious differences right away or one of those who doesn't.

FWIW, I'm in the latter category thus far in this case, although I don't doubt that someone *could* come up with a definite test to make me see a difference. But I see very nice pictures from both, and none of the pictures posted to say, "see, here's a picture so great that it couldn't have been taken with the other lens" strike me that way at all. I'd have to see the identical scene taken with both lenses on the same camera to be convinced of that. But in general, for me, the difference between the lenses would come down to the factors I *know* would matter to me - size&weight, support for quick shift, focal length range, maximum aperture, etc.
01-30-2009, 11:59 AM   #34
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I think Marc pretty much nails the bottom line. The fact that there is actually debate about a sharpness difference should tell us something.

To replace your 18-250 and go to a 2 lens set up, consider the costs involved. (Remember the OP was not interested in getting faster glass, so I am figuring this on the cheap end)

Two lens solution:

Pentax 55-300 $300
Pentax 17-70 $490
Credit on 18-250 -$150

Total cost to switch to a 2 lens configuration with debatable sharpness difference and marginally increased reach:
$640

Is it worth $640? That is the cost of one very nice lens. You could almost get a DA* 50-135 for that, or some nice fast prime lenses. That is why I am saying that you should keep the excellent and versatile lens you have, and if you must spend the money, get a lens that does something you can't do now, like faster glass, or extra wide angle, etc. etc. Or buy a really nice AF-540FGZ flash for your 18-250 indoors (and have some cash left over). If your indoor shooting is such that you can use a flash most of the time, the 18-250 again becomes a very good versatile solution, because just like shooting outdoors, you don't have to worry about large apertures. I shot a once-in-a-lifetime family reunion with my 18-250 and a AF360FGZ (bounced) before I had other lens options, and I was thrilled with the result. I don't think any other lens I own now would have been noticeably better as long as I was using flash anyway.


Last edited by PentaxPoke; 01-30-2009 at 12:16 PM.
01-30-2009, 01:04 PM   #35
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QuoteOriginally posted by Marc Sabatella Quote
But I see very nice pictures from both, and none of the pictures posted to say, "see, here's a picture so great that it couldn't have been taken with the other lens" strike me that way at all. I'd have to see the identical scene taken with both lenses on the same camera to be convinced of that.
I am surprised that someone with your eye cannot see the image of the cat portrait (the second one) and not notice the serious step up from the 18-250 that this image shows. I have seen nothing even close at the tele end from the 18-250.

BTW I own and use the 18-250 regularly ... see here ....
Pentax DA 18-250mm f/3.5 - 6.3 Photo Gallery by alfisti at pbase.com
01-30-2009, 01:32 PM   #36
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QuoteOriginally posted by Alfisti Quote
I am surprised that someone with your eye cannot see the image of the cat portrait (the second one) and not notice the serious step up from the 18-250 that this image shows.
You mean the screen-sized image of the leopard in the snow? Maybe seeing a *full size* version back to back with the identical image taken with the same camera at f/8 with the 18-250 would convince of something. As it is, at the size posted, that shots looks like something my DA50-200 could reproduce easily enough mounted to my K200D (much less with a K20D as Bud used). And I've seen enough of these same sort of apples-to-oranges comparisons like these between the 50-200 and the 18-250 at the tele end to not see any reason to believe there is a huge difference there, either. At screen viewing sizes, I've yet to see any clear difference between *any* of these lenses. Give me 100% crops, and give them to me on comparable images, if you want to convince me there is a significant difference.

BTW, as someone who very rarely posts 100% crops myself, I feel compelled to point out that I also rarely if ever post screen-sized images as proof of the superior resolution of a given lens. Especially when I don't have a correspodning image from any other lens. A screen sized shot can sufficient when you think your intended audience can recognize how their own equipment would fare in producing a similar shot and resized accordingly and if you think the differences would be visible at that size. Or if you are trying to demonstrate that a difference is small enough that it goes away when viewed at screen size.
01-30-2009, 02:30 PM   #37
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QuoteOriginally posted by PentaxPoke Quote
IYou could almost get a DA* 50-135 for that, or some nice fast prime lenses. That is why I am saying that you should keep the excellent and versatile lens you have, and if you must spend the money, get a lens that does something you can't do now, like faster glass, or extra wide angle, etc. etc. Or buy a really nice AF-540FGZ flash for your 18-250 indoors (and have some cash left over).
That's a reasonable way to go, although your numbers seem off, especially if the replacement lens is a 16-45 instead of DA 17-70. An FA 35mm, bounce flash, and Raynox 150 would add versatility to the kit rather than starting over. IF the OP has some specific purpose in mind that the 18-250 would be weak on (birds, architecture etc), then a specialty lens would be good.
01-30-2009, 03:25 PM   #38
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QuoteOriginally posted by audiobomber Quote
That's a reasonable way to go, although your numbers seem off, especially if the replacement lens is a 16-45 instead of DA 17-70.
Also, I'm thinking selling 18-250 would fetch more than $150...

QuoteQuote:
An FA 35mm, bounce flash, and Raynox 150 would add versatility to the kit rather than starting over. IF the OP has some specific purpose in mind that the 18-250 would be weak on (birds, architecture etc), then a specialty lens would be good.
I'm with you on this. If there something specific the lens isn't doing well, then supplement it with one that does that thing better. Don't replace one pretty good general purpose zoom with a couple of different zooms that don't give you any additional capabilities or improve on much. At least, not unless you are 100% convinced that there really is advantage to be had - and I'm not.

02-01-2009, 12:36 PM   #39
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I must say that I'm overwhelmed by the interest that this post has generated, and a big thanks to all for their input; as always greatly appreciated.

I think that the following points summarises this post;

1 The 18-250 is an excellent lens for outdoors work, which is currently its primary use.
2 Changing to a 2 lens setup, which doesn't offer anything new (e.g. extra wide, faster glass), is pretty pointless.

Prime lenses have been suggested, such as the SMC Pentax-DA 40mm Limited.
Such a lens would allow for shooting which cannot, or is difficult to achieve at present.

This raises a further question; why would I purchase such a prime rather than a fast zoom, such as the Tamron 17-50 f2.8

A fast zoom seems to be much more convenient than a prime.
Is there such a noticeable difference in image quality?

Therefore, a 2 lens setup could comprise of the 2 Tamrons, 17-50 and keeping the 18-250 for the extra reach.

Kind regards.
Adrian
02-01-2009, 04:00 PM   #40
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QuoteOriginally posted by bychan Quote
I must say that I'm overwhelmed by the interest that this post has generated, and a big thanks to all for their input; as always greatly appreciated.

I think that the following points summarises this post;

1 The 18-250 is an excellent lens for outdoors work, which is currently its primary use.
2 Changing to a 2 lens setup, which doesn't offer anything new (e.g. extra wide, faster glass), is pretty pointless.
Adrian,
You have summarized my point of view very well. I think you have an excellent lens for your stated purposes, so enjoy it.

Regarding primes, there are a lot of people on this forum that are really "prime experts" and you will find a wealth of information here. I have a few primes, but personally, I am more of a "zoom" shooter most of the time. If you need a fast zoom, the Tamron 17-50 f/2.8 is my personal favorite. In fact my first lens after the 18-250 was the 17-50, and it really is my primary "indoor lens" with the 18-250 my primary outdoor lens. Eventually I got the DA*50-135 for long reach indoors and I use it for portraits as well.

Update: Here is the 18-250 compared against 3 other lenses. Can you tell which is which? https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/49639-4x50-lens-game.html

Last edited by PentaxPoke; 02-01-2009 at 08:38 PM.
02-02-2009, 01:17 AM   #41
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Everyone has their own reasons for prefering primes over zooms or vice versa. I like how small primes are compared to zooms of equivalent quality or speed. Have you *seen* the DA40? Also, if you choose your primes well (eg, if you can deal with manual focus), it's a heck of a lot cheaper to build a "fast" collection of primes to cover a focal length range than to do the same with zooms. For me, those are both reasons to give up the slight convenience advantage of zooms over a well-chosen set of primes.
02-05-2009, 11:20 AM   #42
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QuoteOriginally posted by Marc Sabatella Quote
Everyone has their own reasons for prefering primes over zooms or vice versa. I like how small primes are compared to zooms of equivalent quality or speed. Have you *seen* the DA40? Also, if you choose your primes well (eg, if you can deal with manual focus), it's a heck of a lot cheaper to build a "fast" collection of primes to cover a focal length range than to do the same with zooms. For me, those are both reasons to give up the slight convenience advantage of zooms over a well-chosen set of primes.
Again many thanks for your observations and advice.
On the subject of primes, I've purchased the mentioned DA40mm f2.8 from another forum member. This will hopefully be with me sometime next week.

Regards.
Adrian
02-17-2009, 08:20 PM   #43
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A bit late but here is a comparison ....

Re: DA 18-250 and DA 55-300: Pentax SLR Talk Forum: Digital Photography Review
02-18-2009, 09:09 AM   #44
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Re Dan's (audiobomber) observation:
QuoteQuote:
The 18-250 has serious distortion at 18mm
.....not forgetting to mention some noticeable pincushion distortion at the opposite end of the spectrum.....lol !

Despite all of the above, I still regard Tamron's accomplishment in bringing the 18-250mm super-zoom to the market-place as a remarkable feat and believe Pentax's subsequent licensing of this particular design to be a ringing endorsement to this effect….something along the lines of that old adage about "Imitation being the sincerest form of flattery" etc.
Considering the cost constraints which many of today's engineers probably find themselves operating under, I suspect it is quite likely that they have reached the limit of what is presently achievable, regarding the minimising of optical distortion in super-zooms. This thorny subject is usually referred to as compromise, but fortunately I did plenty of research prior to purchasing this lens and was thus fully aware of the inevitable trade-offs involved where such optical distortions might be concerned. Thankfully these defects can easily be dealt with nowadays when post-processing images and therefore I honestly fail to see the point of this argument, unless you don't have access to a computer.
I don't think anybody here is claiming that Tamron's 18-250mm is perfect in every respect because it clearly isn't, but nonetheless there are evidently many satisfied users out there taking excellent photographs with it any enjoying the all-in-one convenience factor !
The main point of all this is that if you feel a 2-lens solution might offer you a perceivable benefit, simply try it and see.

Best regards
Richard

Last edited by Confused; 02-18-2009 at 04:32 PM.
02-18-2009, 04:36 PM   #45
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QuoteOriginally posted by Confused Quote
I suspect it is quite likely that they have reached the limit of what is presently achievable, regarding the minimising of optical distortion in super-zooms. This thorny subject is referred to as compromise,
I'm not really sure it's much of a compromise, since minor distortion can be dealt with in software (and quite easily in programs like Bibble where the distortion correction is part of the RAW workflow).

I don't recall if this image was at 18mm, but it was taken with the 18-250 in question and exhibited obvious distortion fresh from the camera, but fixing it in Bibble consumed about 5 seconds.
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