[K3Newby]

Hi! Has anyone had success stacking 2 or more rear multipliers? I have K-3, a Pentax 300 F-4 and Pentax 1.4 rear multiplier. Last night while taking pictures of an eagle's nest I wished I had a more ZOOM! But longer lenses are outside of my budget's reach. I'd appreciate any advise on the topic.

[timw4mail]

In general teleconverters / rear multipliers trade "speed" and image quality for reach. If you have a good second teleconverter, and it doesn't affect your image quality too much, go for it.

The only concern I would have is if you have several stacked teleconverters with aperture levers, it could be hard on your camera body.

As is always the case though, a longer dedicated lens will always be better.

[AstroDave]

If you have plenty of light (the Sun!), you can stack at least 3: Magnification Factors for several Kenko Teleconverters on K5 - PentaxForums.com

The images were surprisingly good, but I was stopped down to f11/f13 or so.

[aslyfox]

Hi! Has anyone had success stacking 2 or more rear multipliers? I have K-3, a Pentax 300 F-4 and Pentax 1.4 rear multiplier. Last night while taking pictures of an eagle's nest I wished I had a more ZOOM! But longer lenses are outside of my budget's reach. I'd appreciate any advise on the topic.

Welcome to the forums

lots of members here willing to try to help out

____________________

please recognize that I am a newbie and still trying to gain knowledge [ is taking photos of the sun the same as using stacked " extenders " to photograph wildlife ? ]

but:

you are not alone with the problem

other than the old fashion zoom method [ one ( or more ) steps forward/back keeping an eye out for your surroundings ] no suggestions

the problem is the trade off of using any " extender " on the speed and I Q as mentioned.

today's " extenders " are very much improved over those available years ago when my dad explained it to me but there still is a cost to the use of one

which may be expanded greatly when stacking them [ admittedly I have no personal experience to relate ].

____________________________________________

have you considered renting a " longer " lens when needed. I use Lensrental.com with good effect and there are other companies

problems with renting equipment:

1 you will miss it when you return the lens

2 the costs

3 you won't have it when you need it unless you can plan the encounter

4 the encounter may not happen as planned and you are out the cost of rental
________________________________________________________________________

alternatively consider trying to find an " experienced " lens or an " older " version of what you are seeking if you cannot afford what you want new

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Last edited by aslyfox; 05-01-2018 at 06:29 AM.

[onlineflyer]

Don't know if you're looking to spend some money but the F 1.7x AF would work. However, it would mean giving up some iq, af speed/accuracy, a half stop, and some funds for purchase but it would give you 510mm over your current 420mm.

[photoptimist]

It depends on how you define "success."

Yes, you can stack and get an image.

But you'll probably lose autofocus, need to use higher ISO to compensate for the dimness, and end up with a noisy image that's not very sharp.

The physics of long-focal length optics all but guarantees that good sharp pictures require large expensive lenses.

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Before you try stacking, think carefully about what you really want to achieve in terms of final print size and required resolution. The 24 MPix of the K-3 enables a lot of cropping and with some careful post processing you can get a decent looking large print from a cropped image.

[gaweidert]

Yes, I did it once to photograph a mother grizzly with her three cubs at Yellowstone. She was over a mile away. (It measures out to about 1,800 meters on Google Earth) I tacked a Tamron 1.4x and a Vivitar 2x onto my D FA 150-450 lens. Then mounted it onto my K3. Yes I did get a shot. I figured that I may never see such a thing again, so any shot was better than nothing. I guess i would call the quality passable. I have never tested the combination at anything closer. Equivalent focal length of 1890mm.

Best part was that I caused a minor bear jam and I let a lot of kids and their parents take a peak at them. Only about 10% of the people who go to Yellowstone ever see a bear. People have actually complained to the rangers they they should have the wildlife out where they can see it.

I only found them because I was just sitting at a pullout just looking around and I spotted a tiny brown speck on some snow off in the distance. I looked with my binoculars and verified my hunch. Once I pulled out the tripod and mounted the camera and lens on it people started pulling over.

This is 1/250 sec at ISO 1250.

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Last edited by gaweidert; 05-01-2018 at 06:54 AM.

[normhead]

Hi! Has anyone had success stacking 2 or more rear multipliers? I have K-3, a Pentax 300 F-4 and Pentax 1.4 rear multiplier. Last night while taking pictures of an eagle's nest I wished I had a more ZOOM! But longer lenses are outside of my budget's reach. I'd appreciate any advise on the topic.

My comment would be your 300 ƒ4 isn't wide enough. After quite bit of use with stacked multipliers I don't recommend stacking on anything but 2.8 lenses, and even the, lenses like my Tamron 300 2.8 tell right in the operating notes it can't be used with stacked TCs, and my experimenting would suggest they are right.

But stacking TCs is certainly thing with my DA*200 2.8.

The notion that using a TC isn't as good as a dedicated lens, is pretty much a wives tale. The loss of resolution of the Pentax 1.4 TC is about 3%. That's simply not a visible difference. If your 200mm lens is 5% sharper than your 300mm lens, then even with a 1.5 TC on, the 200 will still be sharper even with the TC, Plus there is usually a pretty substantial weight advantage carrying say a 200 2.8 and TC instead of a 200 and a 300mm lens.

A dedicated lens is better?

DA*200 and 1.4 TC...


Tamron 300 ƒ2.8 and 1.7 TC


I'm not buying that a dedicated lens is better until I see some definitive proof. Theoretically, I don't see how a prime lens with a TC is any different than a longer lens. You've added a few more elements to the back of the lens, external to the lens barrel, but still just a few more elements. The old adage that fewer elements leads to better glass is simply nonsense in this day and age. The opposite is true for CA ad purple fringing. That being said, my DA* 60-250 with the 1.4 TC is definitely better than my A-400. You have to too test these things one combo at a time. General statements do not apply.

[aslyfox]

May comment would be your 300 ƒ4 isn't wide enough. After quite bit of use with stacked multipliers I don't recommend stacking on anything but 2.8 lenses, and even the, lenses like my Tamron 300 2.8 tell right in the operating notes it can't be used with stacked TCs, and my experimenting would suggest they are right.

. . . The notion that using a TC isn't as good as a dedicated lens, is pretty much a wives tale. . . . I'm not buying that a dedicated lens is better until I see some definitive proof. Theoretically, I don't see how a prime lens with a TC is any different than a longer lens. You've added a few more elements to the back of the lens, external to the lens barrel, but still just a few more elements. The old adage that fewer elements leads to better glass is simply nonsense in this day and age. The opposite is true for CA ad purple fringing. That being said, my DA* 60-250 with the 1.4 TC is definitely better than my A-400. You have to too test these things one combo at a time. General statements do not apply.

I, for one, think that modern " extenders " are good and should not be rejected out of hand

as with many things, there are differences between the technology available now and what was available way back then


although I have not tried stacking " extenders " I do use and enjoy my HD Pentax-DA 1.4x AW AF Rear Converter with my other lenses

[Bob 256]

I think your question has two parts - do stacked converters work - which should I spend money on; another converter (cheaper) or a longer lens (less cheap). Right up front, stacked converters work. That said, they multiply. They multiply focal length, f-stop values, and aberrations of the lens they are used with. If you can live with the latter, then it might be acceptable to go the extra converter route but you won't know how bad the aberrations are until you buy and use the extra converter. Two converters could also put undue stress on your lens mount since they extend the connection to the lens significantly and add weight.

Saving up and buying a longer lens might be a better option given it will have single lens performance and should couple to the AF and focusing abilities of the camera. AF with converters is difficult and sometimes impossible since the f-stop ranges so high when using them, making manual focus necessary (and even that can be difficult because of the dim image). Personally, I would use a single converter at times, but wouldn't go for stacked converters except in an absolute emergency.

[normhead]

Personally, I would use a single converter at times, but wouldn't go for stacked converters except in an absolute emergency.

Where as I'm happy to sit out in my blind and get images like this.
DA*200 with stacked 1.4 and 1.7x TCs


To get to 500mm these days I use the Tamron 300 2.8 and 1.7x AF adapter, because I get ƒ4.5 instead of ƒ6.3 with the 1.4 and 1.7 stack on the DA*200. And I'd have the same issue with the DA* 300 ƒ4 and 1.7. my fastest aperture would be ƒ6.3.

But desperate? Really?

It's more like, when I have to carry my gear for miles on a hike, I take the 200, 1.4 and 1.7 in case needed, because they are 1/3 the weight of the 300 2.8 and 1.7. Both have their uses. IQ isn't the issue.

My suspicion is that those who have had trouble with stacked TCs, don't own appropriate DA* quality ƒ2.8 glass.
Most people just don't realize shooting a 200 hand held, you're going to need a tripod. Shooting with a 500mm lens is not the same as shooting with a 200mm lens. Whether 500 is achieved with TCs or not.

[photoptimist]

..... wouldn't go for stacked converters except in an absolute emergency.

LOL!!!!!! I love this concept!

First, I'm trying to imagine an "absolute emergency" in photography. And then I'm trying to imagine one in which "stacked converters" come to the rescue. Perhaps bridezilla is demanding that you snap a close up of her from a 1000 yards?


I'd be interested in Normhead's thoughts on stacked convertors versus simple cropping. At the level of the overall print, I'm very skeptical that a second convertor would provide any image improvement over cropping the picture. And even at the level of 100% pixel peeping, I would not be surprised if the gain in magnification created by the second convertor is offset by a loss in sharpness and an increase in noise.

[K3Newby]

In general teleconverters / rear multipliers trade "speed" and image quality for reach. If you have a good second teleconverter, and it doesn't affect your image quality too much, go for it.

The only concern I would have is if you have several stacked teleconverters with aperture levers, it could be hard on your camera body.

As is always the case though, a longer dedicated lens will always be better.

A lot of good info here!
With the K-3 Cropped sensor I am close 500MM now. My experience (limited) has been the Rear Multiplier hasn't greatly affected my ability to get adequate lighting. But it has affected my ability to hand hold and shoot.
Trying to locate a rental lenses is a good option. And I'm feeling confident that I can stack the multipliers.
It may be time to start lugging the tripod along.

[garywakeling]

Forget tele converters, why not get a used Pentax Q and K mount adapter, fairly cheap and with a magnification crop factor of 5x your reach is amazing even for a 100mm lens

[normhead]

LOL!!!!!! I love this concept!

First, I'm trying to imagine an "absolute emergency" in photography. And then I'm trying to imagine one in which "stacked converters" come to the rescue. Perhaps bridezilla is demanding that you snap a close up of her from a 1000 yards?


I'd be interested in Normhead's thoughts on stacked convertors versus simple cropping. At the level of the overall print, I'm very skeptical that a second convertor would provide any image improvement over cropping the picture. And even at the level of 100% pixel peeping, I would not be surprised if the gain in magnification created by the second convertor is offset by a loss in sharpness and an increase in noise.

You could also argue, just as effectively, that adding a longer lens doesn't make any difference. And you'd have the same types of results. You'd be right up to a point. past that point you'd be wrong. You could prove that a 476mm lens doesn't provide any more detail than a 200 mm lens. Because it doesn't, until it does.

Already dealt with....
Understanding folks saying a TC doesn't ad more detail. - PentaxForums.com

I have to say, this is one of the most persistent misconceptions I deal with here on the forum. Yes you can produce results where you add nothing by using a TC, because the original lens resolves all necessary detail and all the TC does is make it larger.

However, the use of a the Pentax 1,4 TC will produce up to 37% increased resolution on some of the images that the original lens by itself can't resolve. Then you get to the point where even with a TC you can't resolve necessary detail. In two out of three instances the TC makes no difference. But in the middle there's a point where the TC makes a huge difference.

Most people who believe a TC can't make a difference didn't know how to design a test to show when it can. That's the trouble with trying to prove a negative. You can be wrong if your test isn't thorough enough and you don't explore all parameters.