Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
10-06-2021, 10:45 AM   #151
Site Supporter
Site Supporter
MMVIII's Avatar

Join Date: Mar 2008
Location: EU
Posts: 1,002
QuoteOriginally posted by thibs Quote
Because it the past Pentax AF reacted badly to converters.
Of course now that they do offer one (although only APS), they mostly fixed the issue. At least with their own converter.
Sure, but I would not see any need to extrapolate the performance of mechanical coupling and a tube prolonging that for screwdrive AF and apply that to electronic contacts for a modern SDM AF.
If anything could cause a decrease in performance it could maybe be an effective reduction of the focus throw, which could be optimised for performance without converter, but I think even here modern motors can handle that.

10-06-2021, 08:03 PM   #152
Pentaxian
thibs's Avatar

Join Date: Jun 2007
Location: Belgium
Photos: Albums
Posts: 6,651
Completely agree.
Ricoh showed they could handle that properly.
10-07-2021, 08:54 AM   #153
Pentaxian




Join Date: Jul 2011
Posts: 1,925
QuoteOriginally posted by normhead Quote
420 /4 with a 1.4. 600 5.6 doesn't work well with APS-c, maybe for FF at least with my 300 2.8.
A single super telephoto design will not do job. You need two lenses and/r converters... there are converter and there are converters. Good ones, bad ones, ones with factors of 1.4; 1.7; 2... many options.
The Leica lens module design was quite interesting - better results than converters and more physical lenses in the porfolio from less articles. Probably not perfect for AF/digital era.

A 2.8/300 would sell in numbers, but even with TCs it will not become a perfect 600 mm lens. Anything (much) shorter than 560mm will feel short after the oven pipe was released and requires replacement. Anything longer will be too long for APS-C if we are looking at only one lens. A diffractive optics line with 300/500 mm or 400/600 mm FL would be perfect - (Nikon did very well here, w.r.t. to price, performance, size...).

What we will definitely not see will be reincarnations of the 250-600 or a 4/600 - these lenses do not fit to the current lineup and will not sell in significant numbers.
10-07-2021, 09:22 AM   #154
Pentaxian
normhead's Avatar

Join Date: Jun 2007
Location: Near Algonquin Park
Photos: Gallery | Albums
Posts: 38,579
QuoteOriginally posted by zapp Quote
A single super telephoto design will not do job. You need two lenses and/r converters... there are converter and there are converters. Good ones, bad ones, ones with factors of 1.4; 1.7; 2... many options.
The Leica lens module design was quite interesting - better results than converters and more physical lenses in the porfolio from less articles. Probably not perfect for AF/digital era.

A 2.8/300 would sell in numbers, but even with TCs it will not become a perfect 600 mm lens. Anything (much) shorter than 560mm will feel short after the oven pipe was released and requires replacement. Anything longer will be too long for APS-C if we are looking at only one lens. A diffractive optics line with 300/500 mm or 400/600 mm FL would be perfect - (Nikon did very well here, w.r.t. to price, performance, size...).

What we will definitely not see will be reincarnations of the 250-600 or a 4/600 - these lenses do not fit to the current lineup and will not sell in significant numbers.
A 600 f/4 will never be as portable as my 300 2.8, which I can carry in a rectangular camera bag. As for the 300 2.8 with a 2x on a K-1, it's pretty darn good. The advantage to 600 4, in my experience is I've seen Nikon guys put a 1.4 on them with excellent results. The 2x maxes out the 300 2.8.

10-07-2021, 12:03 PM   #155
Pentaxian
KiloHotelphoto's Avatar

Join Date: Jan 2015
Location: Glen Mills, PA
Photos: Albums
Posts: 908
Norm have you ever tried stacking a 1.4 and 2x on your 300 2.8? I've seen a guy do it with a Canon 400 2.8 not sure if it's possible with Pentax.

The images didn't look bad on the back of his camera but who knows how they looked once he downloaded them.
10-08-2021, 05:06 AM   #156
Forum Member




Join Date: Jul 2014
Posts: 88
QuoteOriginally posted by normhead Quote
A 600 f/4 will never be as portable as my 300 2.8, which I can carry in a rectangular camera bag. As for the 300 2.8 with a 2x on a K-1, it's pretty darn good. The advantage to 600 4, in my experience is I've seen Nikon guys put a 1.4 on them with excellent results. The 2x maxes out the 300 2.8.
Some of these paintents look like they might be for a larger chip version of the 645
10-08-2021, 06:03 AM   #157
Pentaxian
normhead's Avatar

Join Date: Jun 2007
Location: Near Algonquin Park
Photos: Gallery | Albums
Posts: 38,579
QuoteOriginally posted by KiloHotelphoto Quote
Norm have you ever tried stacking a 1.4 and 2x on your 300 2.8? I've seen a guy do it with a Canon 400 2.8 not sure if it's possible with Pentax.

The images didn't look bad on the back of his camera but who knows how they looked once he downloaded them.
I did the 1.4 and 1.7 just yesterday. Never tried it with the 2x.


In my experience, people who need more reach will try anything although closer with a shorter lens is always better if possible.

The above image isn't going to make it into my album which is essentially one of my best images of every bird but, I suppose in the right circumstance that combo might produce a best in class type photo. This is what it would have to match.


Taken from here.
https://www.flickr.com/photos/149541448@N08/albums/72157683751426530/with/51196435500/


Last edited by normhead; 10-08-2021 at 06:18 AM.
10-15-2021, 09:47 AM   #158
Senior Member




Join Date: Apr 2013
Photos: Gallery
Posts: 267
QuoteOriginally posted by Wheatfield Quote
Excellent news. And with shake reduction in the lenses working in conjunction with IBIS, telephoto shooters are going to enjoy this.
QuoteOriginally posted by normhead Quote
That would end a huge disadvantage for Pentax shooters. If I can't stabilize my camera hand held, the camera won't lock focus. But, these are just patents. let's not get too excited too fast. It does show what they are thinking in terms of future development. I just can't get excited before they are announced.
I see this statement just now. How did you get to that conclusion? Your focus system works with the speed of light. And the speed of the camera processor. And the speed of your lens motor. Maybe your are not able to maintain the subject in the expanded focusing area, but usually we photographers are not shaking that much, are we? Sure we see a shaky image in the view finder, but the focusing should work anyway.

Could you explain please?
10-15-2021, 10:18 AM - 1 Like   #159
Pentaxian
Wheatfield's Avatar

Join Date: Apr 2008
Location: The wheatfields of Canada
Posts: 13,695
QuoteOriginally posted by UlrichSchiegg Quote
I see this statement just now. How did you get to that conclusion? Your focus system works with the speed of light. And the speed of the camera processor. And the speed of your lens motor. Maybe your are not able to maintain the subject in the expanded focusing area, but usually we photographers are not shaking that much, are we? Sure we see a shaky image in the view finder, but the focusing should work anyway.

Could you explain please?
Using a long lens hand held is something of a challenge. Any small movement by the photographer is magnified greatly in the viewfinder. Put a shake reduction system in the lens, and suddently the viewfinder image becomes still (presuming an optical viewfinder, in a mirrorless system it matters not where the shake reduction system resides).
This makes holding a focus point much easier.

If you have a long lens for your Pentax, see how much easier it is to keep the image still using live view, where you are seeing what the sensor sees compared to looking through the viewfinder.
10-15-2021, 10:25 AM   #160
Site Supporter
Site Supporter




Join Date: May 2019
Photos: Albums
Posts: 5,127
QuoteOriginally posted by Wheatfield Quote
Using a long lens hand held is something of a challenge. Any small movement by the photographer is magnified greatly in the viewfinder. Put a shake reduction system in the lens, and suddently the viewfinder image becomes still (presuming an optical viewfinder, in a mirrorless system it matters not where the shake reduction system resides).
This makes holding a focus point much easier.

If you have a long lens for your Pentax, see how much easier it is to keep the image still using live view, where you are seeing what the sensor sees compared to looking through the viewfinder.
Yeah, I have a Sigma 400/5.6 and if I'm tired it's complicated for me to even frame properly. The lens is very light (~800 g) considering the FL, so the center of gravity is on the camera... which means that the front element sways like crazy with the smallest vibration.
10-15-2021, 05:44 PM   #161
Pentaxian
normhead's Avatar

Join Date: Jun 2007
Location: Near Algonquin Park
Photos: Gallery | Albums
Posts: 38,579
^ What they said.
10-16-2021, 06:18 AM   #162
Senior Member




Join Date: Apr 2013
Photos: Gallery
Posts: 267
What they said is a different topic. Where is the problem why the AF shouldn't work.
10-16-2021, 06:31 AM   #163
Pentaxian
normhead's Avatar

Join Date: Jun 2007
Location: Near Algonquin Park
Photos: Gallery | Albums
Posts: 38,579
QuoteOriginally posted by UlrichSchiegg Quote
What they said is a different topic. Where is the problem why the AF shouldn't work.
How and where did that become the topic?

If you're talking about why the AF doesn't work with TC,s it's light loss. I have absolutely no problem using any TC including stacked and TC on my Tamron 300 2.8 AF. The cut-off point would seem to be ƒ8.5. If you have an ƒ/5.6 lens and put a 2x TC on it, now you're at ƒ11 , not enough light coming though the viewfinder for the AF system to function. The only 5.6 lenses I know that work with TC work with the HD DA 1.4. Pentax AF is rated to be most efficient at ƒ/2.8. Every stop after that degrades AF performance. But it really doesn't become critical until the total combination is less than ƒ8.

If that's not what you're asking, I'm not sure what is.

Last edited by normhead; 10-16-2021 at 06:37 AM.
10-16-2021, 06:32 AM - 1 Like   #164
Pentaxian
thibs's Avatar

Join Date: Jun 2007
Location: Belgium
Photos: Albums
Posts: 6,651
QuoteOriginally posted by UlrichSchiegg Quote
What they said is a different topic. Where is the problem why the AF shouldn't work.
If your AF points are bouncing everywhere, how can you expect AF to work reliably ?
10-16-2021, 06:43 AM   #165
Site Supporter
Site Supporter




Join Date: May 2019
Photos: Albums
Posts: 5,127
QuoteOriginally posted by UlrichSchiegg Quote
What they said is a different topic. Where is the problem why the AF shouldn't work.
Because if you already have difficulty maintaining the OVF steadily on the target, PDAF sensels are going to be jumping all over the subject and will have a very hard time locking focus. Even if you were trying to AF on a static subject, it would turn into a high-intensity 3D tracking situation for the camera.
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!
560mm, 600mm, camera, da, da 55-300 plm, da560, diameter, front, image, kg, length, lens, lenses, pentax, pentax news, pentax rumors, plm, post, pound, price, range, shutter, subject, sync, telephoto lens design, tripod, weight
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
New half mirror OVF&EVF Hybrid Viewfinder patent OoKU Pentax News and Rumors 45 01-08-2021 12:43 PM
Is the D FA* 50/1.4 a Pentax/ Ricoh design or a Tokina design? Wheatfield Pentax SLR Lens Discussion 60 06-28-2020 03:15 PM
ricoh files patent on 2 Q lens designs and on 4/3 design! shaolen Pentax News and Rumors 20 08-21-2014 12:03 AM
Fuji files a new patent for sensor design...... Eric Auer Non-Pentax: Canon, Nikon, Sony, etc. 1 01-30-2014 03:43 AM
FA Limited lens series won the 2010 Good Design Long Life Design Award Patriot Pentax SLR Lens Discussion 26 11-29-2010 06:16 AM



All times are GMT -7. The time now is 02:26 PM. | 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