Sigma 18-300mm F3.5-6.3 DC Macro HSM (Contemporary) TC Compatibility

ndzinn · 10-23-2019, 11:22 AM

Does anyone know if the Sigma 18-300mm F3.5-6.3 DC Macro HSM (Contemporary) is compatible with the Pentax DA 1.4x rear converter (TC). If so, how's the IQ?

Adam · 10-23-2019, 12:34 PM

The TC officially supports lenses up to F5.6, so I'd expect the AF to start struggling a ways into the zoom range.

I haven't used the combo but it should work otherwise. That said, I'd be skeptical of the benefit in terms of reach.

**Lowell Goudge** · 10-23-2019, 05:30 PM

I would not spend the money on a tc for the lens you are using. You would be very disappointed with the results as the TC will magnify the flaws.

Yes it might function, but......

TCs in my experience work well if a) they are really high quality, and b) the lens they are attached to is also high quality.

I use the sigma TCs on my sigma 70-200/2.8 EX and get great results, but, the sigma TCs only work with a very limited number of high end sigma lenses as the TC front element actually protrudes into the lens barrel. Also note that the sigma TCs don’t support HSM for Pentax mount, only screw drive, and except if I recall correctly do not support any cropped sensor lenses, only full frame (and as I said, high end lenses including the 300/2.8, and 500/4.5 and only one or two others including the 70-200/2.8)

rr1736 · 10-23-2019, 07:31 PM

I believe you need a lens which is F4 or faster with the converter

**Manichorse** · 10-24-2019, 01:59 AM

Not sure if i've got the right Sigma Lens (18-300 F3.5 -6.3 DC) , but I do have the Pentax 1.4TC, so I thought i'd give the combo a try with my K-70. No Post-processing, just resampled down. 1st no TC wide. 2nd No TC 300mm. 3rd TC - 300mm.

ndzinn · 10-24-2019, 03:04 AM

Originally posted by Manichorse

Not sure if i've got the right Sigma Lens (18-300 F3.5 -6.3 DC) , but I do have the Pentax 1.4TC, so I thought i'd give the combo a try with my K-70. No Post-processing, just resampled down. 1st no TC wide. 2nd No TC 300mm. 3rd TC - 300mm.

I appreciate all the responses.

The main difference in the EXIF for the second and third photo is a bump in the ISO from 1600 too 3200, one stop, the TC, I'd suppose. This at f/6.3. Tough for me to evaluate IQ, but seems the combo works. Nice experiment, Manichorse. Thanks.

10-23-2019, 11:22 AM	#1
ndzinn New Member Join Date: Jul 2019 Location: Texas Posts: 17	Sigma 18-300mm F3.5-6.3 DC Macro HSM (Contemporary) TC Compatibility Does anyone know if the Sigma 18-300mm F3.5-6.3 DC Macro HSM (Contemporary) is compatible with the Pentax DA 1.4x rear converter (TC). If so, how's the IQ?

10-23-2019, 12:34 PM	#2
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,595	The TC officially supports lenses up to F5.6, so I'd expect the AF to start struggling a ways into the zoom range. I haven't used the combo but it should work otherwise. That said, I'd be skeptical of the benefit in terms of reach. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

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10-23-2019, 05:30 PM	#3
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,888	I would not spend the money on a tc for the lens you are using. You would be very disappointed with the results as the TC will magnify the flaws. Yes it might function, but...... TCs in my experience work well if a) they are really high quality, and b) the lens they are attached to is also high quality. I use the sigma TCs on my sigma 70-200/2.8 EX and get great results, but, the sigma TCs only work with a very limited number of high end sigma lenses as the TC front element actually protrudes into the lens barrel. Also note that the sigma TCs don’t support HSM for Pentax mount, only screw drive, and except if I recall correctly do not support any cropped sensor lenses, only full frame (and as I said, high end lenses including the 300/2.8, and 500/4.5 and only one or two others including the 70-200/2.8)

10-23-2019, 07:31 PM	#4
rr1736 Senior Member Join Date: Sep 2011 Location: Chicago Illinois Photos: Albums Posts: 203	I believe you need a lens which is F4 or faster with the converter

10-24-2019, 03:04 AM	#6
ndzinn New Member Join Date: Jul 2019 Location: Texas Posts: 17 Original Poster	Originally posted by Manichorse Not sure if i've got the right Sigma Lens (18-300 F3.5 -6.3 DC) , but I do have the Pentax 1.4TC, so I thought i'd give the combo a try with my K-70. No Post-processing, just resampled down. 1st no TC wide. 2nd No TC 300mm. 3rd TC - 300mm. I appreciate all the responses. The main difference in the EXIF for the second and third photo is a bump in the ISO from 1600 too 3200, one stop, the TC, I'd suppose. This at f/6.3. Tough for me to evaluate IQ, but seems the combo works. Nice experiment, Manichorse. Thanks.