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12-29-2011, 09:24 PM   #1
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Teleconverter for Sigma 100-300mm lens

I have a Sigma lens (100-300mm) and I wanted to use a teleconverter to increase it's zoom capacity. Can anyone suggest me what my options are for the teleconverter.

12-29-2011, 09:51 PM   #2
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Which Sigma lens do you have? The link points to the general Sigma section.

If you have the fast one with constant F4 then a 1.4x or even a 2x will work. If will be a F5.6 or F8 lens which will still support auto focus. Depending on what you plan to shoot and the lighting conditions, the quality can be maintained to some degree with top teleconverters. The main concern is that now you be shooting at 1 or 2 stops lower so you'll have to use longer speeds or higher ISO to compensate. Furthermore you'll probably have to stop down the lens a bit to maintain quality. Overall you'll be shooting at F8-F11 to maintain your F4 quality.

If on the other hand have the slow 100-300 lens then don't even try. It is too slow and not worth it.

Unless you are shooting under very optimal conditions, my recommendation will be to shoot at 300 and then crop the image. A small digital enlargement from a sharp image is better than from a teleconverter most of the times .
12-29-2011, 09:57 PM   #3
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If it is constant f4 model Sigma's own 1.4x & 2x TC will work, although the 2.0 AF is slow @ times (1.4 TC has almost no loss of IQ and AF works fine). No idea how other TC's work with this lens. If your lens is not the constant f4 model I would suggest you not waste your time.
12-29-2011, 11:44 PM   #4
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thanx a lot for all your input.
My lens is Sigma 100-300mm f/4.5-f/32
From what I understand, the teleconverter won't be the best option for my lens, might as well buy a better telescopic lens. any suggestions. Please keep in mind I am a beginner, have Pentax k-r

12-30-2011, 06:29 AM   #5
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Just note that sigma's tc's won't work on that lens. Also note that the lens will not autofocus as any TC combined with the lens will be below thie minimum speed (aperture) requirements for AF to work
12-30-2011, 08:18 AM   #6
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QuoteOriginally posted by apocalypse.v Quote
might as well buy a better telescopic lens. any suggestions. Please keep in mind I am a beginner, have Pentax k-r
What is with this lens that you don't like? Is it its quality, the focal reach or the very slow speed at longer focal lengths (F6.7 @ 300mm)?

What type of photographs you like to take that require a better/longer lens? Is it wild life, sports, surveillance, etc.?

Do you plan to photograph fast moving subjects or can you use a tripod for long exposures?

The above variables will determine what is best for your needs. The 300mm end of your zoom should cover more than 90% of most situations, but it is so slow it is only usable during daytime in very good lighting.

Let us know and we'll try to help make the right decision.
12-30-2011, 10:05 AM   #7
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QuoteOriginally posted by demp10 Quote
What is with this lens that you don't like? Is it its quality, the focal reach or the very slow speed at longer focal lengths (F6.7 @ 300mm)?

What type of photographs you like to take that require a better/longer lens? Is it wild life, sports, surveillance, etc.?

Do you plan to photograph fast moving subjects or can you use a tripod for long exposures?

The above variables will determine what is best for your needs. The 300mm end of your zoom should cover more than 90% of most situations, but it is so slow it is only usable during daytime in very good lighting.

Let us know and we'll try to help make the right decision.
The 300mm is good but images are not sharp enough. I would like to use it for sports and wild life photography. Hope the info helps you suggest me good options.
12-30-2011, 11:36 AM   #8
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QuoteOriginally posted by apocalypse.v Quote
The 300mm is good but images are not sharp enough. I would like to use it for sports and wild life photography. Hope the info helps you suggest me good options.
I think I left out another very important aspect: your budget.

You have two groups of options: A prime lens (fixed focal length at 300mm) or a zoom that reaches at 300mm.

Generally speaking, primes will give you better quality images, will be faster and will cost more. Zooms are much more flexible, cost usually less and some of them are quite good.

If you are comfortable using Manual focus that will open a lot of inexpensive options, but trying to do sports and wild life on the move, it will most likely require to use auto focus. For sports, shutter speed is important so you need a fast lens. You can increase the ISO of course but a faster lens will give you more options. Another consideration is if you plan to use a tripod/monopod at all times. Most fast primes (and fast zooms) are too heavy for comfortable handheld photography.

If it is within your budget and want to go the prime way, then the Pentax DA-300mm F4 may be a good choice.

If you gravitate toward a zoom (which will be my recommendation) the Pentax DA 55-300mm is very good at 300mm even wide open at F5.8 and costs very little. Along with the kit lens (18-55) makes a very good compact travel kit that you can take it anywhere.

There are other choices for zooms that will reach 300mm from Tamron and Sigma, but the DA 55-300 will give you the best value.

Another thing to remember is shooting at 300mm is not easy. Even with SR on, you need to maintain a fairly high speed (at least 1/200) and use some support (e.g. a monopod). Use as high ISO as you can stand the noise. A grainier picture is better than a fuzzy one.

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