[photoptimist]

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.

Thanks! Nice tests!

Those 1:1 crops certainly show how a very high quality lens that is out-resolving the sensor can resolve more of the scene with a teleconverter. The question is: by how much does the 200/2.8 out-resolve the sensor? Your tests show that it's probably at least 1.7X but is it much more than that? But does a lens with one teleconverter still out-resolve the sensor enough to benefit from a second teleconverter? It's too bad you did not post the 1:1 crop image of the green tea box with 200+1.4X+1.7X stack, because that's the situation we're try to test here.

You are right that it's impossible to make universal statements about dedicated ultra-long lenses versus TC-stacked-medium-telephoto lenses. There's crappy long glass out there that would fail that test. But then there's also lower-quality medium-telephoto lenses that don't out-resolve the sensor and would deliver more detail with a single TC let alone stacking.

If you rank all the ways to achieve a 600 mm focal length (which seems to be what the OP is trying to do by stacking a second TC to a 300/4+1.4X), I'd think that 300/4+1.4X+1.4X would not be very high on the list compared to a good dedicated 600 or a good 450 + 1.4X. The 300/4 probably needs to be stopped down to f/5.6 to get the best degree of out-resolution but then the double-stacked 1.4Xs create an f/11 aperture that's starting to show some diffraction. The stacked 300/4 would probably beat the Opteka 650-1300mm. It all depends on how much the 300/4 out-resolves the sensor.


P.S. back in the dark ages of film they sold 3X teleconverters! I had one of those as well as a 2X. Stacked, the 6X images were best described as oatmeal (mushy and grainy from the high-ISO film). Even a wide-open f/2.8 lens was pushed to a dim diffraction-softened f/17.

[normhead]

Thanks! Nice tests!

Those 1:1 crops certainly show how a very high quality lens that is out-resolving the sensor can resolve more of the scene with a teleconverter. The question is: by how much does the 200/2.8 out-resolve the sensor? Your tests show that it's probably at least 1.7X but is it much more than that? But does a lens with one teleconverter still out-resolve the sensor enough to benefit from a second teleconverter? It's too bad you did not post the 1:1 crop image of the green tea box with 200+1.4X+1.7X stack, because that's the situation we're try to test here.

You are right that it's impossible to make universal statements about dedicated ultra-long lenses versus TC-stacked-medium-telephoto lenses. There's crappy long glass out there that would fail that test. But then there's also lower-quality medium-telephoto lenses that don't out-resolve the sensor and would deliver more detail with a single TC let alone stacking.

If you rank all the ways to achieve a 600 mm focal length (which seems to be what the OP is trying to do by stacking a second TC to a 300/4+1.4X), I'd think that 300/4+1.4X+1.4X would not be very high on the list compared to a good dedicated 600 or a good 450 + 1.4X. The 300/4 probably needs to be stopped down to f/5.6 to get the best degree of out-resolution but then the double-stacked 1.4Xs create an f/11 aperture that's starting to show some diffraction. The stacked 300/4 would probably beat the Opteka 650-1300mm. It all depends on how much the 300/4 out-resolves the sensor.


P.S. back in the dark ages of film they sold 3X teleconverters! I had one of those as well as a 2X. Stacked, the 6X images were best described as oatmeal (mushy and grainy from the high-ISO film). Even a wide-open f/2.8 lens was pushed to a dim diffraction-softened f/17.

That's what I like, a complicated answer, because in my experience, to most of these questions, there's no simple answer. Most of the misconceptions people have were caused by not looking beyond, the most simple explanation.

Unfortunately with TC's people tend to think of it as a cheap way of getting long lenses. A DA*200 is close to the cost of the DA*300 ƒ4. And the 1.4 TC is $600. The cost of the 200 and1.4 far exceeds the cost of the 300 ƒ4. It's not the cheap way to go if you want 300. But it's cheaper than a 300ƒ4 and a 200 2.8 and lighter to carry. You're paying for bit of convenience, it's not cheaper. That is where the most of the confusion comes from. People say I'm going to take my consumer quality lens and stick a TC on for more range. Those people make up the vast majority of those who legitimately claim you can do the same thing by enlarging the image.

My A-400 was like that. It was an acceptable lens on it's own, but it really wasn't anything special with a TC on it.

[photoptimist]

That's what I like, a complicated answer, because in my experience, to most of these questions, there's no simple answer. Most of the misconceptions people have were caused by not looking beyond, the most simple explanation.

Unfortunately with TC's people tend to think of it as a cheap way of getting long lenses. A DA*200 is close to the cost of the DA*300 ƒ4. And the 1.4 TC is $600. The cost of the 200 and1.4 far exceeds the cost of the 300 ƒ4. It's not the cheap way to go if you want 300. But it's cheaper than a 300ƒ4 and a 200 2.8 and lighter to carry. You're paying for bit of convenience, it's not cheaper. That is where the most of the confusion comes from. People say I'm going to take my consumer quality lens and stick a TC on for more range. Those people make up the vast majority of those who legitimately claim you can do the same thing by enlarging the image.

My A-400 was like that. It was an acceptable lens on it's own, but it really wasn't anything special with a TC on it.

Good points!


You've raised another crucial issue -- teleconverter quality -- which would literally be doubly as important in the case of stacking. It may be that part of the myth that "teleconverters can't add detail" comes from so many people having so many cheap $99.99 teleconverters (in addition to the problem of adding teleconverters to lower-quality lenses).

Of course, if successful stacking requires a high-quality f/2.8 prime plus two high-quality teleconverters, then we're back to the original point about costs. Sharp, long-telephoto images are expensive no matter how you stack it.

[normhead]

Good points!


You've raised another crucial issue -- teleconverter quality -- which would literally be doubly as important in the case of stacking. It may be that part of the myth that "teleconverters can't add detail" comes from so many people having so many cheap $99.99 teleconverters (in addition to the problem of adding teleconverters to lower-quality lenses).

Of course, if successful stacking requires a high-quality f/2.8 prime plus two high-quality teleconverters, then we're back to the original point about costs. Sharp, long-telephoto images are expensive no matter how you stack it.

A month or so ago I was shooting beside guy with a Nikon 600 ƒ4 and a TC on for birding. It took awesome images. SO the snotty TC answer is, if you pay $8500 for your lens and 5 hundred for your TC it works great.

Or in the Pentax world, if you pay the big bucks for a DA* quality telephoto (apparently including the DFA 150-450) it works great. As a way to try and squeeze more performance out of consumer grade lenses, it's not really a viable solution. A successful combination depends on both (or all three) elements being above consumer quality.

[K3Newby]

I think my K-3 combo (300MM f-4 plus 1.4 Auto Teleconverter) takes decent pictures. The two deer were captured at Cahokia Mounds State Park around 7 PM recently. These are unretouched, but highly resized images.
The eagles nest is highly cropped, but does clearly show the eagle. I'm still trying to sort out a way to get physically closer to the nest. I'll have to get some water float shoes, so I can walk across water!

[JimJohnson]

(sorry I've been too busy for this forum for a few months)

Hmmm, something not pointed out in this thread is cropping. I have a TC I use with my film kit because I shoot transparencies. Unless you digitize them (these days, printing also includes digitization), what comes out of the camera is what you get. However, the K-3 (ii) has plenty of resolution to toss some away in a digital crop unless you are making exceptionally large prints or the subject isn't sharp to begin with.

If you cannot afford a longer lens or high quality TCs, do not rule out cropping as an alternative to adding glass. As a side benefit, your bag will be lighter. I'll bet even Mr. Norm has done a fair amount of cropping in his time and still had saleable images.

[ima poster]

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.

I would use as few multipliers as possible. a single 1.4x is probably ok, but stacking them will degrade the image quality to a greater extent than the pixel resolution of the camera. Or to put it a different way, I would use the 1.4x and then crop and zoom on the PC. The K-3 has a good number of pixels and so can take a fair amount of zoom (1.4x would be no issue at all) for normal viewing. Certainly the way to go for viewing on a monitor and also for prints - depending on the print size.