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02-26-2017, 06:38 AM   #1
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Long Lens Options Using Teleconverter

Hi Folks,

I tried to post this on the "300mm Club" forum, but couldn't seem to break the code to post a new thread,....so here I am, hoping to get some suggestions on long zoom lenses for a k-50. I have an extra K-50 body that is presently naked.

Some background,...I have a Sony a77ii and just put a Minolta 500mm mirror AF lens on it last week. I am REALLY enjoying it! So, I started a search for a similar lens for my K-50. Turns out there are many similar lenses that can be adapted to Pentax, but used or new, they are all MF lenses. Folks on the DPReview Pentax forum gave me lots of input and I'm convinced that MF will not work for me on a long zoom lens.

I have considered all of the long zoom options from Sigma and Tamron, and a few from Pentax. Although these are great choices for some folks, I'm a hand held shooter and these lenses start at about 4 1/2 pounds. Size and weight are important to me, and my search is now turning to other options, such as 55-300, 70-300 etc, paired with a teleconverter.

I have never used a teleconverter and am interested in any combination that retains autofocus and is not too heavy.

Thanks for any suggestions!

Jack

02-26-2017, 06:57 AM   #2
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Hello,
Maybe you should specify about what you shoot, do you shoot at night ? what price are you willing to pay?

Matt
02-26-2017, 07:30 AM   #3
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Hi Matt,

I shoot mainly wildlife and normally in pretty good light, locally and in Teton and Yellowstone Parks,........ certainly not at night.

What would I pay? Well, I originally budgeted for a Tamron 150-600mm and similar lenses for my Sony, about $600-800 bucks. These are not for me, simply too large and heavy.

I now am looking for something costing less, and lighter.The k-50 is one of several DSLRs I use, including a K-70 with 55-300mm. So, I'm thinking of a Sigma or Tamron 55-300mm or something similar, but adding a teleconverter.

I know nothing about teleconverters though, and I want to reach a minimum of 600mm equivalent.

I'll lose interest completely unless there is a teleconverter that retains autofocus/

Thanks,...Jack

Last edited by Setter Dog; 02-26-2017 at 07:33 AM. Reason: clarity of message
02-26-2017, 08:14 AM   #4
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There are 2x autofocus converters about,one being a Tamron. The problem with this scheme is that in doubling your focal length you likewise double your f-stop number. The loss of light will play havoc with autofocus except in the very best conditions. You will often be forced to use the widest aperture which is usually the least desirable in term of optical performance. In addition, the added optical elements introduce losses which do affect image quality. A long telephoto with a 2x teleconverter will work but I think you will be disappointed in the results.A 1.4x teleconverter introduces fewer losses but will not get you anywhere near your goal of 600mm.

02-26-2017, 09:03 AM   #5
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My limited experience has been that you need a very good lens and very good TC for this to work. Otherwise you're probably better off just cropping. In the Pentax APS world I think you're looking at the Pentax TC plus maybe a Pentax 300/4.

Also remember any typical consumer-grade zoom that goes to 300mm isn't going to perform as well at 300mm vs. shorter settings. Even most better zooms don't perform as well at their longer settings.
02-26-2017, 09:51 AM   #6
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QuoteOriginally posted by Setter Dog Quote
Hi Folks,

I tried to post this on the "300mm Club" forum, but couldn't seem to break the code to post a new thread,....so here I am, hoping to get some suggestions on long zoom lenses for a k-50. I have an extra K-50 body that is presently naked.

Some background,...I have a Sony a77ii and just put a Minolta 500mm mirror AF lens on it last week. I am REALLY enjoying it! So, I started a search for a similar lens for my K-50. Turns out there are many similar lenses that can be adapted to Pentax, but used or new, they are all MF lenses. Folks on the DPReview Pentax forum gave me lots of input and I'm convinced that MF will not work for me on a long zoom lens.

I have considered all of the long zoom options from Sigma and Tamron, and a few from Pentax. Although these are great choices for some folks, I'm a hand held shooter and these lenses start at about 4 1/2 pounds. Size and weight are important to me, and my search is now turning to other options, such as 55-300, 70-300 etc, paired with a teleconverter.

I have never used a teleconverter and am interested in any combination that retains autofocus and is not too heavy.

Thanks for any suggestions!

Jack
if you want a relatively good combo of length speed and weight, this is a tough option,........ but what about an M or A 300/4, combined with a pentax SMC-F 1.7X AF Converter. it gives you a 510mm selective focus range AF lens for under 1 kilo. i have the K300/4 which is a little heavier, but still easy to hand hold
02-26-2017, 02:47 PM - 1 Like   #7
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Long reach and light weight is a difficult combination to find. I've been through various combinations to get a balance of weight, reach, IQ, reasonable AF performance and affordability that suits me. Nothing is perfect; it's a compromise.

There are various Sigma zooms in K-mount that go to 400mm or beyond. I had the 170-500, which was one of the lightest ones at about 1.4kg. That's a fair weight to lug around, but a big difference from a DFA 150-450 or a Sigma 150-500 or 50-500, which are all around 2kg. I found it quite useable hndheld, with some practice. However the results I got from that lens on the K-30 above 300mm were not great when the subject was more than about 10m (say 30 feet) away. (Might have done better on the K-3.)

At the other end of the weight scale you have the consumer xx-300 zooms. I have the DA-L 55-300 and recently bought the DA 55-300 WR PLM. Each is a good lens, even at 300. But when you put a 1.4x teleconverter on a lens you lose one stop of light. So 300 f5.8 becomes the equivalent of roughly 420mm f8; 300 f6.3 becomes roughly 420mm f9. And that is wide open - I find the DA-L particularly needs to be stopped down at f8 or so for better sharpness at 300, so you may need to stop down further. Those numbers are really only useful in ideal conditions: you need very bright light, both because the AF will struggle to focus and because you will need fairly high shutter speeds and ISO values. And a teleconverter will magnify any limitations in the lens. I would question whether the game is worth the candle. The results may be better just from using the lens without a TC and cropping - especially if you later get a camera with a 24mp sensor.

In between are the combination of prime and TC. The sweet spot for me in K-mount, for more reach than 300, is the F/FA*300 f4.5 with a 1.4x TC. The IQ is very good even with the TC. These previous-generation primes weigh about 850-900g, so even with a TC they aren't much over 1kg, which is quite manageable handheld and not too bad to carry. You are then getting the equivalent of 420mm f6.3, and the lens is very good wide open. And used without the TC, they are so sharp that images will stand a lot of cropping (especially with the K-3). These lenses are surprising compact, although very dense.

BTW, not all teleconverters are created equal. The DA 1.4x WR one seems very good but is expensive. At the other end putting a poor quality TC on a consumer standard lens seems a sure recipe for disappointment.

One lateral suggestion. Normally I would say spend the money on a lens, but for telephoto shooting you would get good bang for buck from upgrading the body from 16mp to 24mp, especially to a K-3 which has much better AF than the K-30/K-50. A used K-3 can be had for around $US500 or so, so it would only be a $250-300 upgrade.


Last edited by Des; 02-26-2017 at 02:56 PM.
02-27-2017, 04:49 AM   #8
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QuoteOriginally posted by Des Quote
Long reach and light weight is a difficult combination to find. Snip...........


One lateral suggestion. Normally I would say spend the money on a lens, but for telephoto shooting you would get good bang for buck from upgrading the body from 16mp to 24mp, especially to a K-3 which has much better AF than the K-30/K-50. A used K-3 can be had for around $US500 or so, so it would only be a $250-300 upgrade.
Why not go really lateral and get a Pentax Q, with a 300-300mm lens and go MF

The Q has a pixel densirtv equivalent to 250MP in a full frame body.
02-27-2017, 05:36 AM   #9
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Thanks very much for the replies everyone.

Lots of good stuff to study and digest. I think I get the message, a consumer grade lens with a teleconverter would not be satisfactory. That idea is off my list now.

DPReview Pentax forum, a member uses a Tokina AF 80-400mm and likes it. I found some reviews by other Pentax users and they were very good. In fact, of all the lenses reviewed by Pentax users, the Tokina is rated the best.

Anyone else using this Tokina 80-400mm?

Jack
02-27-2017, 03:24 PM   #10
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QuoteOriginally posted by Lowell Goudge Quote
Why not go really lateral and get a Pentax Q, with a 300-300mm lens and go MF

The Q has a pixel densirtv equivalent to 250MP in a full frame body.
Lots of people like this combination, and I have seen some very good images. The things that would put me off it - with handheld use in mind - are the lack of viewfinder, and a sense that the Q body is too small to handle easily with a large lens. But I haven't tried it so this is just my preconception. And I would still prefer AF for wildlife - even after using MF exclusively for about 25 years on my old film SLR. Maybe I've just gone soft.
02-27-2017, 04:07 PM   #11
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QuoteOriginally posted by Setter Dog Quote
Thanks very much for the replies everyone.

Lots of good stuff to study and digest. I think I get the message, a consumer grade lens with a teleconverter would not be satisfactory. That idea is off my list now.

DPReview Pentax forum, a member uses a Tokina AF 80-400mm and likes it. I found some reviews by other Pentax users and they were very good. In fact, of all the lenses reviewed by Pentax users, the Tokina is rated the best.

Anyone else using this Tokina 80-400mm?

Jack
Tokina AT-X 80-400mm F4.5-5.6 Lens Reviews - Tokina Lenses - Pentax Lens Review Database
02-27-2017, 05:27 PM   #12
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80-400 F4.5-5.6 Tokina - PentaxForums.com
Zoom: Tokina 80-400 vs Sigma 120-400 vs Pentax 55-300: Pentax SLR Talk Forum: Digital Photography Review
Tokina AT-X 840 AF D 80-400 mm f/4.5-5.6 review - Introduction - LensTip.com
Hard to find, and not particularly cheap.

According to the reviews, might need to be stopped down to f8 for decent results above 300mm. Weighs about 1kg, which is lighter than the Sigma xx-400 lenses, but i would say that the F*/FA*300 lens + TC would a better option at around the same weight and bulk, if your budget will run a little further. These are really premium lenses.
02-27-2017, 07:28 PM - 1 Like   #13
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QuoteOriginally posted by Des Quote
Lots of people like this combination, and I have seen some very good images. The things that would put me off it - with handheld use in mind - are the lack of viewfinder, and a sense that the Q body is too small to handle easily with a large lens. But I haven't tried it so this is just my preconception. And I would still prefer AF for wildlife - even after using MF exclusively for about 25 years on my old film SLR. Maybe I've just gone soft.
I bought an eBay Nikon knock off viewfinder 5 for their P&S cameras to get I level view finder, and use a cannot 100mm macro knock off collar (with suitable leather spacer ) to support this with a monopod.

My best 200mm lens so far from results is the vivitar series 1. 70-210/3.5 version 1 which is very sharp and not bad at all for fringing.

Works pretty good.
02-28-2017, 04:34 AM   #14
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QuoteOriginally posted by Des Quote
80-400 F4.5-5.6 Tokina - PentaxForums.com
Zoom: Tokina 80-400 vs Sigma 120-400 vs Pentax 55-300: Pentax SLR Talk Forum: Digital Photography Review
Tokina AT-X 840 AF D 80-400 mm f/4.5-5.6 review - Introduction - LensTip.com
Hard to find, and not particularly cheap.

According to the reviews, might need to be stopped down to f8 for decent results above 300mm. Weighs about 1kg, which is lighter than the Sigma xx-400 lenses, but i would say that the F*/FA*300 lens + TC would a better option at around the same weight and bulk, if your budget will run a little further. These are really premium lenses.

Hi Des,

Thanks for another specific and valid recommendation. I think that combination might work for me. As I understand it, there are two Pentax 300mm lens, The F and the FA. Are these equally suitable for my purposes?

I'll need a TC, as you suggest. If you could specify a specific TC or two that work well, could you send me that recommendation. Or, maybe someone else is using a certain TC effectively and would recommended it.

You're very helpful, Des. Thank you,

Jack
02-28-2017, 04:57 AM   #15
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QuoteOriginally posted by Setter Dog Quote
As I understand it, there are two Pentax 300mm lens, The F and the FA. Are these equally suitable for my purposes?
Yes they are optically identical. The F has a tripod collar and a slide out hood, which the FA doesn't, although you can get a cheap aftermarket tripod collar for the FA and the reverse-mounting hood it comes with is very good. The F is a little lighter. But the F is harder to find. Check out the reviews of these lenses - people love them.

QuoteOriginally posted by Setter Dog Quote
I'll need a TC, as you suggest. If you could specify a specific TC or two that work well, could you send me that recommendation.
@WildMark did a comparison here of a few different model 1.4x TCs. There was one Sigma that he liked, but not all Sigmas will fit all lenses. I have the Kenko 1.5x pz TC, which despite the name is really 1.4x; it is the same as the Tamron 1.4x pz TC. The pz indicates that it will work (theoretically) with lenses that have SDM or DC autofocus; most TCs won't. The Kenko/Tamron is fine, in my experience. The gold standard is the Pentax DA 1.4x WR TC, but it's really expensive.
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