[BAKrueger]

I read a few years ago that the Pentax 1.4x tele-converter would not work on lenses with smaller than f4.0. I have newly purchased the 150-450mm 4.5-5.6 and the k-3iii, had been using the 1.4x converter for few years now with my k-3i and the 300mm f4.0. Today I put the 1.4x converter between the k-3iii and the 150-450 and it focuses just fine!! I don't know if it's new with the k-3iii or the 150-450mm or it was a made up all along. Pictures acceptably sharp.

[boriscleto]

The initial advertising for the 150-450 showed it being used with the 1.4.

[aslyfox]

i think the concern was with the autofocus when using slower lenses, check the in depth review:

Conclusion
The rear converter has no significant effect on autofocus speed at normal light levels as long as lenses F4 or faster are used. In dim light the loss of one F-stop of light with the converter will result in slower autofocus, as the camera will require more time to make up for the lost stop of light while making its calculations.

For lenses slower than F4, contrast detect (live view) AF works best while viewfinder AF may be unreliable.
. . .

We would not recommend using the 1.4x Rear Converter with wide lenses or with consumer zooms like the SMC Pentax-DA 50-200 F4-5.6 or 55-300mm F4-5.8 lens due to autofocus limitations. Viewfinder (phase detect) autofocus works best with lenses F4 or faster (live view must be used for reliable AF with slower lenses), and the converter amplifies lens flaws so it is preferable to use it in connection with top shelf lenses only

.

Read more at: https://www.pentaxforums.com/reviews/pentax-da-14x-aw-af-rear-converter/conc...#ixzz6uDHq34Xb

my only problem with using the D FA 150-450mm with the teleconverter is trying to hold it steady enough to shoot without a monopod or tripod

some times I can, other times, it is very hard to do so

[luftfluss]

This site even reviewed the 1.4x with the 150-450: Testing the HD Pentax-DA 1.4x Teleconverter with the D FA 150-450mm on Full Frame Review - Introduction | PentaxForums.com Reviews

[BAKrueger]

i think the concern was with the autofocus when using slower lenses, check the in depth review:

.

Read more at: Pentax-DA 1.4x AW AF Rear Converter Review - Conclusion | PentaxForums.com Reviews

my only problem with using the D FA 150-450mm with the teleconverter is trying to hold it steady enough to shoot without a monopod or tripod

some times I can, other times, it is very hard to do so

That's not a problem for me I always use support

best regards Brian

---------- Post added 05-07-21 at 02:18 PM ----------

This site even reviewed the 1.4x with the 150-450: Testing the HD Pentax-DA 1.4x Teleconverter with the D FA 150-450mm on Full Frame Review - Introduction | PentaxForums.com Reviews

OOOps I missed that

Regards Brian

[aslyfox]

That's not a problem for me I always use support

best regards Brian . . .

if you ever are caught without support and have to try, here is a good article on some techniques that might help you out

Making the Most of Long Exposure Handhelds
Introduction
In this attempt to understand concepts second nature to all veterans of a militarized basic training, we explore the four fundamentals of marksmanship and how they apply to improving one's photographic technique.. . .

I am by no measures a "pro," but I understand my fundamentals very well, and this specific set has been drilled into my head so many times that it is now second-nature. I am going to teach you how to "shoot" your camera like a high end rifle because at the end of the day, the fundamentals stay the same in every aspect. If you are an avid shooter (of the projectile type), then you do all of this probably without even thinking about it, especially if you are like some of my friends that exited the womb wielding a 30 Aught Six (7.62mm for those of you unfamiliar with American calibers).

Or, if you are like me and never touched a weapon until your adult life by way of raising your right hand, your Drill Sergeants provided that intimate, patient instruction and guidance that makes you think of warm country evenings at home with grandma: Steady Position, Breathing Control, Aiming and Sight Picture, and Trigger (Shutter) Squeeze. . . .

Read more at: Making the Most of Long Exposure Handhelds - Introduction - In-Depth Articles

[Lowell Goudge]

This issue has been going on since the early1990’s where Pentax has always been conservative with the AF function with small apertures. I own an original, from 1991 Pentax F-1.7x AF converter.

It is specified to work with F2.8 and faster lenses. When I bought it, Pentax let me try it out on my PZ1 with a series 1 70-210/3.5 and it worked just fine. I checked it with my M100/4 macro and again worked fine, same with my K300/4, it would not AF on my 400/5.6 vivitar lens however.but they under stated maximum aperture even back then by a full stop.

[othar]

but they under stated maximum aperture even back then by a full stop.

They obviously like to play it safe. Better to set low expectations and get praised than the other way around

[asahi67]

I have used the same combo on my K3-no problems. I now have the combo on my K3 III and it is even better! Enjoy.

[Mbaez]

I use the 1.4 with the 55-300 plm on my KP without problems.

[5ks]

I wonder if it's mostly relative to the amount of light. Normally any autofocus system works best in bright daylight, right? Will the DFA 150-450 with a teleconverter (1.4x) focus well also in low light (using a tripod)? Handheld, I suppose it will need a lot of light anyway, to get the exposure time fast enough, so the focusing is also easier and faster.

[mocker]

I cant make proper photos with K3 + 150-450 + 1.4 TC.
K1 + 140-450 + 1.4 TC the only proper photos were made with electronic shutter.
I am eager to test on K3III.

[simsburyphoto]

I am new owner of the 150-450. I will have to try it with the 1.4x on my KP and K1ii and see how it works.

[MrNPhoto]

I cant make proper photos with K3 + 150-450 + 1.4 TC.
K1 + 140-450 + 1.4 TC the only proper photos were made with electronic shutter.
I am eager to test on K3III.

What do you mean? What about the combo is giving you problems?