Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
08-15-2018, 03:04 PM   #1
New Member




Join Date: Aug 2018
Posts: 9
question on tele conveter lenses

Hello,

I have a Vivitar 2XMC4 AF tele converter lens.

Its been working great with my SMC 55-300mm lens for long range shots.

I had that crazy thought, can I stack 2 or more tele converter lenses (2 of the same type converters) for more range?

Yes I realize that there will be a loss of light and some visual details, but for the sake of distance, will Pentax Cameras (I have a K10D and a K-70) recognize more than one tele converter is connected and still auto focus?

Thanks.

08-15-2018, 03:58 PM   #2
Loyal Site Supporter
Loyal Site Supporter
THoog's Avatar

Join Date: Aug 2012
Location: North Carolina
Photos: Gallery | Albums
Posts: 3,573
QuoteOriginally posted by midnightvisions Quote
will Pentax Cameras ... recognize more than one tele converter is connected and still auto focus?
I don't think the body knows or cares that a teleconverter is mounted - it only knows whether it is getting enough light to lock focus. The TC may have "passthru" contacts so that the lens' ID information is reported to the body, and some TCs are smart enough to translate the reported focal length, but some aren't.

I've stacked TCs before. The results were mush, but through the viewfinder, it was handy as a spotting scope.
08-15-2018, 05:07 PM - 1 Like   #3
Loyal Site Supporter
Loyal Site Supporter




Join Date: May 2016
Location: East Coast
Posts: 1,532
I think you would do much better to upsample the pictures than stack TCs.
08-15-2018, 05:40 PM   #4
Site Supporter
Site Supporter
mikeSF's Avatar

Join Date: Jan 2009
Location: East Bay Area, CA
Photos: Gallery
Posts: 6,015
In both of my rigs, using teleconverters and even stacking two teleconverters is always better than cropping the non TC image to achieve same framing of subject. ymmv.

08-15-2018, 05:51 PM   #5
Loyal Site Supporter
Loyal Site Supporter




Join Date: May 2016
Location: East Coast
Posts: 1,532
QuoteOriginally posted by mikeSF Quote
always better than cropping
That's not been my experience, but to be clear, I don't mean cropping, but resampling to what the equivalent focal length is. I've been playing around with the DFA 150-450 (and a few others) and the Pentax 1.7x AF/TC and a K3II and K1. I'd like to get my hands on the DA* 300, but the 150-450 is so good I'm finding it hard to justify.
08-15-2018, 07:37 PM   #6
Loyal Site Supporter
Loyal Site Supporter




Join Date: May 2007
Location: Flagstaff, Arizona
Posts: 312
I've triple-stacked TCs - on the sun - PLENTY of light: Magnification Factors for several Kenko Teleconverters on K5 - PentaxForums.com

The results weren't too bad, and certainly better than trying to upsample in this case.
08-16-2018, 04:36 AM   #7
Loyal Site Supporter
Loyal Site Supporter




Join Date: May 2016
Location: East Coast
Posts: 1,532
I think the bottom line is go try it with the specif lens and TC combination that you have. Setup on a good tripod and do a series of shots stepping down from wide open with and without the TCs, and then go do some pixel peeping.

Just in general, I find a certain satisfaction in taking a series of test shots of the same subject. e.g. front of house, neighbors chimney, etc., with different lenses, and then being able to go back and do some quick IQ comparisons on how they perform when questions come up. Of course, my girlfriend probably thinks I'm nuts as I once again head out the front door with a large tripod and camera gear in tow.
08-16-2018, 08:21 AM   #8
Site Supporter
Site Supporter
mikeSF's Avatar

Join Date: Jan 2009
Location: East Bay Area, CA
Photos: Gallery
Posts: 6,015
QuoteOriginally posted by clickclick Quote
That's not been my experience, but to be clear, I don't mean cropping, but resampling to what the equivalent focal length is. I've been playing around with the DFA 150-450 (and a few others) and the Pentax 1.7x AF/TC and a K3II and K1. I'd like to get my hands on the DA* 300, but the 150-450 is so good I'm finding it hard to justify.
If your reason for using a teleconverter is to fill the frame with your subject, then you are cropping 50-75% of your pixels away in the non-TC image; when you upsample to arrive at the same image size as the lens+TC image.

08-16-2018, 08:29 AM - 1 Like   #9
Pentaxian
Site Supporter
normhead's Avatar

Join Date: Jun 2007
Location: Near Algonquin Park
Photos: Gallery | Albums
Posts: 30,576
QuoteOriginally posted by clickclick Quote
That's not been my experience, but to be clear, I don't mean cropping, but resampling to what the equivalent focal length is. I've been playing around with the DFA 150-450 (and a few others) and the Pentax 1.7x AF/TC and a K3II and K1. I'd like to get my hands on the DA* 300, but the 150-450 is so good I'm finding it hard to justify.
I'd be interested in a visual explanation of your experience.

Here's mine
Understanding folks saying a TC doesn't ad more detail. - PentaxForums.com

For all the times I've heard this anti-TC sentiment, I've never seen an actual post that in any way corroborated the sentiment with real world examples. It seems to be one of those "easy to say, difficult to prove" kind of statements. There are parameters to be followed for sure. But blanket statement that TCs aren't better than enlarging in every instance is just wrong, and in the above post, I've demonstrated why.

According to my experimentation the reason you think that would be that the lens you used could resolve the necessary detail without the TC. If there is no additional detail to be resolved, of course the TC doesn't add anything. it's when your original lens can't resolve all the detail you desire that the TC improves the image.

The evidence I presented is pretty much indisputable. But, I'm always open to new evidence. Opinions unsupported by evidence, not so much.

Last edited by normhead; 08-16-2018 at 08:44 AM.
08-16-2018, 08:58 AM - 1 Like   #10
Loyal Site Supporter
Loyal Site Supporter




Join Date: May 2016
Location: East Coast
Posts: 1,532
QuoteOriginally posted by normhead Quote
I'd be interested in a visual explanation of your experience.

Here's mine
Understanding folks saying a TC doesn't ad more detail. - PentaxForums.com

For all the times I've heard this anti-TC sentiment, I've never seen an actual post that in any way corroborated the sentiment with real world examples. It seems to be one of those "easy to say, difficult to prove" kind of statements. There are parameters to be followed for sure. But blanket statement that TCs aren't better than enlarging in every instance is just wrong, and in the above post, I've demonstrated why.

According to my experimentation the reason you think that would be that the lens you used could resolve the necessary detail without the TC. If there is no additional detail to be resolved, of course the TC doesn't add anything. it's when your original lens can't resolve all the detail you desire that the TC improves the image.

The evidence I presented is pretty much indisputable. But, I'm always open to new evidence. Opinions unsupported by evidence, not so much.
I will see if I can get some samples posted in the next day. I'd love to find out I'm doing something wrong and get more use out of my TC. I have no problem eating my own hat as part of the learning experience. In a nutshell, I took a series of shots with and without the TC, upsampled the non-TC shots, and did a bunch of pixel peeping trying to compare the detail levels. It seemed I would have occasional shots with the TC that were better, but over all, I was getting better results without the TC. I'll definitely post back here with what I have.

And I didn't think I had worded my sediments as a factual blanket statement - my "I think" was to indicate an opinion to explore, not a fact. Sorry if it didn't come across that way - part of why my later post about trying with specific gear to see what happens. I think there are very few absolutes anywhere in life or photography.
08-16-2018, 10:21 AM - 1 Like   #11
Site Supporter
Site Supporter
mikeSF's Avatar

Join Date: Jan 2009
Location: East Bay Area, CA
Photos: Gallery
Posts: 6,015
I suspect this is rig specific. I did testing on my 2 rigs and as a result I have no hesitation mounting a TC or even stacking 2 TCs as needed on a shoot.
Given a lesser quality TC, cropping may do better.
08-16-2018, 11:24 AM - 1 Like   #12
Loyal Site Supporter
Loyal Site Supporter




Join Date: May 2016
Location: East Coast
Posts: 1,532
QuoteOriginally posted by mikeSF Quote
I suspect this is rig specific. I did testing on my 2 rigs and as a result I have no hesitation mounting a TC or even stacking 2 TCs as needed on a shoot.
Given a lesser quality TC, cropping may do better.
I think you are probably correct on this assesment. it's going to be a bit before I can get everything I did sorted out and posted, but in the meantime, as I was looking at buying a TC, I found some reviews by @Wild Mark that are similar to my experience. Here are a couple of his reviews:

Sigma X1.4 Tele Converter AF Lens Reviews - Miscellaneous Lenses - Pentax Lens Review Database

Tamron-F 1.4X Pz-AF MC4 Lens Reviews - Miscellaneous Lenses - Pentax Lens Review Database

One of the things I've run into with my Pentax 1.7x AF/TC is a fair amount of chromatic abberation. There seems to be lot of purple fringing. And one of the lenses I've wanted to play with it on is my Takumar 4.5/500, which has it's share of CA as well. I am finding my 150-450 does better than the 500. Part of my "better" evaluation is the range of usable F stops. I do think there is a defniite sweet spot where the TC and a given lens play well, but you can't always count on being able to use that. This then puts me in the scenario of trying to figure out what combination is going to give me the greatest chance of success.

The fun thing about all this is it's just like a big puzzle. I like analysis and getting my hands on things, so this is a great imputus to go do some more expiramentation. More soon.

Last edited by clickclick; 08-16-2018 at 01:15 PM.
08-16-2018, 01:52 PM - 1 Like   #13
Site Supporter
Site Supporter




Join Date: Jun 2010
Location: Seaside CA
Posts: 450
Some teleconverters are better than others. A four element converter reduces sharpness more than six or seven element converters. Takumar K mount converters are four element converters. Pentax converters are higher quality. The lens you use it on makes a difference. I used my Pentax 1.4x on my 85mm f/2 and got good results but putting it on my 85mm FA 1.4 was ugly. I also used the 1.4x on my 300mm and got good results. My Pentax 2X always seemed to be not quite as good as I wanted, but better than a four element. In other words, you will need to do testing.
08-16-2018, 02:13 PM - 1 Like   #14
Pentaxian
Site Supporter
normhead's Avatar

Join Date: Jun 2007
Location: Near Algonquin Park
Photos: Gallery | Albums
Posts: 30,576
QuoteOriginally posted by pentaxus Quote
Some teleconverters are better than others. A four element converter reduces sharpness more than six or seven element converters. Takumar K mount converters are four element converters. Pentax converters are higher quality. The lens you use it on makes a difference. I used my Pentax 1.4x on my 85mm f/2 and got good results but putting it on my 85mm FA 1.4 was ugly. I also used the 1.4x on my 300mm and got good results. My Pentax 2X always seemed to be not quite as good as I wanted, but better than a four element. In other words, you will need to do testing.
Personally, I don't recommend TCs for less than DA* equivalent glass or on focal lengths less than 70mm. And I only recommend the Pentax HD DA 1.4 or Pentax F 1.7x AF Adapter,

Too many people say they don't work well for me to issue any blanket statements about all TCs. I've tried my TCs on my worst lens an M 135 Vivitar 2.8, and they just make the badness (softness coupled with CA and purple fringing) 1.4 and 1.7 times more visible.

But on my DFA 100 macro, DA* 60-250, DA* 200 2.8, and Tamron SP AF 300 2.8 they work great. If you are using lower quality glass, all bets are off.

TCs don't help you get the most out of average glass, TCs help you get the most out of high quality glass, glass that out-resolves your sensor by a considerable margin that can still crank out the lw/ph even when enlarged.
08-17-2018, 04:24 AM   #15
New Member




Join Date: Aug 2018
Posts: 9
Original Poster
Thank you for the feedback and suggestions.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
converter, k-mount, lens, lenses, pentax lens, question on tele, range, slr lens, tele
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Question on Pentax tele-converter and SDM lens. Teaman Pentax SLR Lens Discussion 4 06-11-2017 07:47 PM
D FA 150-450mm with 1.4x conveter Shakey Pentax SLR Lens Discussion 32 01-11-2017 09:33 AM
2X Conveter Charles1 Pentax DSLR Discussion 4 03-11-2012 03:14 PM
Just Scored a Tele Takumar 200mm F5.6 and a Tele Takumar 300mm F6.3! Colorado CJ Pentax SLR Lens Discussion 20 01-22-2012 05:53 PM
Stupid stacked tele question nakey Pentax SLR Lens Discussion 2 01-27-2009 10:59 AM



All times are GMT -7. The time now is 03:24 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top