Which 18-250: Pentax or Sigma?

Started Mar 2, 2012 | Discussions
Anirut J
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Which 18-250: Pentax or Sigma?
Mar 2, 2012

Pls recommend which 18-250 will be suitable for my needs:

  • Fast focusing speed in all kinds of lighting situations, from bright noon to dim bars.

  • Good for journalism style, immediate, capturing the moment and people more than making fine arts.

  • Pictures will not be printed. Mostly for web use. And if printed, will probably not be larger than A3+ size (17"x19").

  • I may need to add a TC to extend the longer end in some cases. And would adding a TC hinder the focusing speed?

  • For use on my K-r (for now).

I'm torn between these two lenses. If I understand correctly, the Pentax seems to give somewhat better pic quality, but I don't know about its focusing speed. I also don't know if the Sigma's HSM will be any faster enough to justify the drop in pic quality.

And, are the differences in pic quality of these two lenses far apart? Or pretty close? Or which one will have an edge over the other in some ways or in certain lighting situation?

Also, is the on-lens SR on the Sigma better than Pentax's in-body SR to be of any consideration?

(My friend has a mint, rarely-used Pentax 18-250 sitting at home that he's willing to sell me but a new Sigma's cheaper)

Sorry for the lengthy details. Thanks in advance, everyone.
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powerslave
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Re: Which 18-250: Pentax or Sigma?
In reply to Anirut J, Mar 2, 2012

I dont own the sigma so no comparison help there, but I prefer the Pentax 18-250 focus speed over the Pentax 55-300. Its not bad

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steephill
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Re: Which 18-250: Pentax or Sigma?
In reply to Anirut J, Mar 2, 2012

You may be very disappointed with these lenses in dim light or when using a TC. At the long end these are very slow, f6.3 for Pentax for example. Add a 1.4x TC and you will be down to f9 wide open. AF will really struggle with so little light. And these lenses aren't exactly at their best wide open needing to be stopped down by 2 stops particularly for border resolution.

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hanhait
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Re: Which 18-250: Pentax or Sigma?
In reply to Anirut J, Mar 2, 2012

The difference between these lenses will be marginal and not noticeable in practice, they both obey the same laws of optics and physics, so feel free to toss a coin. The Pentax is equivalent to the same Tamron, and Sigma and Tamron differ very little in that lens.

I wonder if such a lens can do what you need; do you really need such a strong tele reach ? I wonder if a 17-70 or 16/18- 50 would not suit you better.

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DAVID MANZE
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Re: Which 18-250: Pentax or Sigma?
In reply to hanhait, Mar 2, 2012

Hi,

The Pentax 18-250mm is a design by tamron, the Pentax is discontinued but the Tamron remains.It must be said that since pentax discontinued there version it's value S/H has remained high. Reviews can be found of both lenses on LensTip.com but reviews seem to vary considerably,Photozone for example rates the P/T quite well whereas LensTip doesn't.

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If your friend has a copy for sale at least you could take the opportunity to test it and see if it is a well centered copy!
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amicus70
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Re: Which 18-250: Pentax or Sigma?
In reply to Anirut J, Mar 2, 2012

Why using a DSLR with just one lens? The idea behind a DSLR is, that you could pick on every single occasion the lens you need. Often the apeture is the problem with such lenses you want to buy. Perhaps a Super-Zoom-Bridge-Camera is an option?

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GPGeneralPhoto
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Re: Which 18-250: Pentax or Sigma?
In reply to Anirut J, Mar 2, 2012

I have the Pentax version. This lens will auto focus with a TC. Picture quality was not as bad as I thought it would be. But good?...Eh. All hand held, overcast day.

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geru
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Re: Which 18-250: Pentax or Sigma?
In reply to Anirut J, Mar 2, 2012

I have both the Kr and Pentax 18-250 the lens is my walk around lens and it's a great lens for general purpose uses it's not designed for low light and is near useless in those conditions.

The Sigma goes for nearly $500 on Amazon/us and if you're friend is trying to sell you a used Pentax for near that amount I'd question his friendship. I paid $325 brand new 2 years ago granted it was on sale but the going price at the time was around $375.

You need to be looking for a much faster lens maybe two lenses. Something like a 70-200 f2.8 or Pentax 50-135 f2.8 and maybe a prime like the newer Pentax 35mm f2.4 (mainly for it's low price) the IQ is really quite good even at that price.

I'd stay away from using a TC in low light unless of course you have no problem using very high ISO (s) like 6400.

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gaddigad
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Re: Which 18-250: Pentax or Sigma?
In reply to Anirut J, Mar 2, 2012

According to reviews I have seen the Tamron re-bundled Pentax (and the oem version) is better than the Sigma.

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Anirut J
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Let me clarify the ambiguities of my needs ...
In reply to Anirut J, Mar 2, 2012

Thanks for all the suggestions so far ... the answers seem to slant towards the Pentax/Tamron 18-250.

However, I very well understand that I'm trading picture quality for versatility.

For my needs, I just CAN NOT be changing lenses (let alone carry many) when I'm taking pictures during military exercises. I'm running with the soldiers in the fields with all that dust. I need to capture the moments, at any givin point, at any lighting situation, from pictures of soldiers runing in the sun and then turning around taking pics of those hiding deep in the shadows inside buildings.

I may be at the observation post with the big guys, taking pictures in limited space of the people and atmosphere where I'll need to use the wide to normal end. And then, suddenly, a jet comes screaming in for a bombing run and I'll need to use the long tele end immediately.

I just have to forget about the luxury of having the time to change lenses. I love nice sharp pics like everyone else would. But I need to "capture the moment". A decent pic is better than no pic at all. This is neither advertising work nor fine arts.

I think my needs should be clear this time ... Sorry for not making it more 'specific' earlier in the starting post.

OK, so, is the HSM of the Sigma 18-250 better/faster at focusing in most situations compared to the screw-driven Pentax/Tamron? And does the Sigma work with TC? And will working with TC slow down the focusing speed for both brands?

Please ...

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Anirut J
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Re: Which 18-250: Pentax or Sigma?
In reply to GPGeneralPhoto, Mar 2, 2012

Thanks for the comparison pics.

Seems the 2.0 TC is better than the 1.7 ...

Was there any noticable drop in focusing speed when using the TC?
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brandrx
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Re: Let me clarify the ambiguities of my needs ...
In reply to Anirut J, Mar 2, 2012

Anirut J wrote:

Thanks for all the suggestions so far ... the answers seem to slant towards the Pentax/Tamron 18-250.

However, I very well understand that I'm trading picture quality for versatility.

For my needs, I just CAN NOT be changing lenses (let alone carry many) when I'm taking pictures during military exercises. I'm running with the soldiers in the fields with all that dust. I need to capture the moments, at any givin point, at any lighting situation, from pictures of soldiers runing in the sun and then turning around taking pics of those hiding deep in the shadows inside buildings.

I may be at the observation post with the big guys, taking pictures in limited space of the people and atmosphere where I'll need to use the wide to normal end. And then, suddenly, a jet comes screaming in for a bombing run and I'll need to use the long tele end immediately.

I just have to forget about the luxury of having the time to change lenses. I love nice sharp pics like everyone else would. But I need to "capture the moment". A decent pic is better than no pic at all. This is neither advertising work nor fine arts.

I think my needs should be clear this time ... Sorry for not making it more 'specific' earlier in the starting post.

OK, so, is the HSM of the Sigma 18-250 better/faster at focusing in most situations compared to the screw-driven Pentax/Tamron? And does the Sigma work with TC? And will working with TC slow down the focusing speed for both brands?

Please ...

The Sigma is an HSM lens and would require a teleconverter with Pz_AF in it's name. I doubt that a 2X Pz_AF would even work. A Tamron 1.4X Pz_AF or Kenko 1.5X PZ_AF might work but I don't really know.

The Pentax can use almost any autofocusing teleconverter such as the cheap Vivitar 1.4X or 2X teleconverters. The Pentax can not use any of the Sigma teleconverters because the front element of the Sigma TC's will hit the rear element of the Pentax lens.

Any teleconverter will slow down the autofocusing speed of the lens it is attached to.

I feel for you having to shoot under such conditions. The best I can reccomend is to use either of the lenses without trying to use a teleconverter with it.

If I was shooting under those conditions I think I would make due with the Pentax DA 18-135mm f3.5/5.6 DC WR lens. For my longer needs I would just crop from the 135mm shot.

Good luck.

Ron

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Anirut J
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Re: Let me clarify the ambiguities of my needs ...
In reply to brandrx, Mar 2, 2012

Thanks, Ron, for you answer. You're the one when it comes to long tele's!

Would you suggest the 18-135 + 2.0 TC? This will give me a normal - long tele use with a little drop in focusing speed (and 2 stops of lost light).
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minzaw
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Re: Let me clarify the ambiguities of my needs ...See the samples and YOU decide !
In reply to brandrx, Mar 2, 2012

I have used pentax 18-250 mm mainly for travels as a travelling/walk around companion

My option is to carry one lens only i.e 18-250mm is my choice for travel when you DO NOT have time to change lens when once in a lifetime photo opportunities in a flash and not to miss such scenarios .
It is meant for an UNCONTROLLED -non studio environment situations only.
I have NO experience with TC.
see sample images with 18-250 mm Pentax 18-250

enjoy
good luck in your selection

minzaw

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brandrx
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Re: Let me clarify the ambiguities of my needs ...
In reply to Anirut J, Mar 2, 2012

Anirut J wrote:

Thanks, Ron, for you answer. You're the one when it comes to long tele's!

Would you suggest the 18-135 + 2.0 TC? This will give me a normal - long tele use with a little drop in focusing speed (and 2 stops of lost light).

I do not recommend any of the HSM. SDM, or DC lenses with the use of any 2X teleconverter. I have a Tamron 2X Pz_AF and a Kenko/Tokina 2X Pz_AF and neither will even attempt to drive any of my SDM lenses. They will drive the 18-135mm DC lens but will not lock on focus. The only HSM lens I have is the Sigma 50-500mm OS HSM which does work with my 1.4X(1.5X) Pz_AF teleconverters.

I will only use any 2X teleconverter with high quality lenses of f4.5 or faster (mostly prime lenses)

If I were you I would get the idea of a 2X teleconverter out of your mind. I am fairly certain you will be disapointed if you continue to go down that route.

If the Pentax 18-135mm DC WR lens is not enough (with cropping) to suit your needs then the best I can say is to use the Sigma 18-250mm OS HSM without a teleconverter, or the Pentax 18-250mm without a teleconverter. Then if you wish to experiment with a teleconverter, find a Tamron 1.4X PZ_Af, Kenko 1.5X PZ_Af, or (for the Pentax only) the Vivitar 1.4X. The Vivitar can be found new for about $90. The other two are no longer made and have to be found used. They have been selling for outrageous prices ($250 and more) on ebay.

One last thing, if I'm not mistaken, the Sigma 18-250mm, because it is HSM, can be focused manually like the Pentax Qucik Shift lenses. The Pentax 18-250mm does not have Quick Shift and has to have the camera in MF to be able to focus manually.

Good luck.

Ron

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Anirut J
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Re: Let me clarify the ambiguities of my needs ...
In reply to brandrx, Mar 2, 2012

Thanks again, Ron, for your fine insights in the matter.
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Anirut J
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Re: Let me clarify the ambiguities of my needs ...See the samples and YOU decide !
In reply to minzaw, Mar 2, 2012

Thanks, minzaw, for the pics.

(Only wish someone share some pics from the Sigma too)
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Patrick T. Kelly
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Re: Which 18-250: Pentax or Sigma?
In reply to amicus70, Mar 2, 2012

amicus70 wrote:

Why using a DSLR with just one lens? The idea behind a DSLR is, that you could pick on every single occasion the lens you need. Often the apeture is the problem with such lenses you want to buy. Perhaps a Super-Zoom-Bridge-Camera is an option?

That's not why I shoot with a DSLR. Your reason might not be everyone's reason.
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GPGeneralPhoto
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Re: Which 18-250: Pentax or Sigma?
In reply to Anirut J, Mar 3, 2012

Anirut J wrote:

Thanks for the comparison pics.

Seems the 2.0 TC is better than the 1.7 ...

Was there any noticable drop in focusing speed when using the TC?
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The Soligor 1.7x TC is better for focus speed. IIRC the 2x made the camera hunt a bit. As to IQ, neither is great, but I suppose both would be OK for your use. BTW the Soligor 1.7x TC is the same as the Promaster 1.7x and is actually 1.5x.
If you will be in dusty dirty conditions, maybe you would need WR.

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gustabod
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Re: Which 18-250: Pentax or Sigma?
In reply to Anirut J, Mar 3, 2012

I had the Sigma 18-250 HSM, used on K20 and K7. Shot friend's wedding and took it travelling. Soft images, slow to get focus in low light (I am talking sunset time, not night time), distortion, the list goes on. No i would not recommend it at all.

You would be better off with a 17-70 sigma or even an 18-125 Sigma (yes I also have both, the 17-70 quite frankly is way better than the 18-125).

I sold the 18-250, it looks good on paper, but unfortunately is more useful as a paperweight. If I went that way again I would look at the Tamron as has been recommended here. In my case I now use primes.
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