[lithedreamer]

I have the fortune to have an HD 1.4x Teleconverter come into my possession. I'm not sure if it suits my shooting style, though. What do you guys use yours for?

[marcusBMG]

This is a tech blurb I wrote for an ad - may offer some insight:

Teleconverters have been a standard piece of optical kit in the film era. They provide a quick and effective means of multiplying the focal length of the lens to get more of a subject filling the frame. 1.4x, 1.5x, 2x are the most common magnifications. They come with matching male/female mounts on each side and fit on a same mount lens between the lens and the camera (not to be confused with adaptive lenses that attach to the lens like a filter).
However with digital there are other options:

1. Use a camera with more megapixels. More MPx = a bigger image with more latitude to crop.
2. Use a camera with a smaller sensor. Using a lens with a camera with a smaller sensor will result in a narrower field of view. The "crop factor" is a measure of how much narrower compared to 35mm film. Note that ads on ebay describing eg a 500mm lens as "750mm" because most "APSC" sensor cameras have a crop factor of 1.5× are misleading. The focal length of a lens is fixed and doesn't change, can't change. The main change is the field of view. But this is really just "cropping in the camera".
3. Using in camera "digital magnification". This is just cropping and resizing the image and is best done on the PC rather than in the camera.

These digital options have one big advantage over TC's: there is no loss (attenuation) of light, your exposure settings remain the same. With a 1.4x TC you lose approx one stop: so for example a 400mm f4 lens +1.4x TC becomes a 560mm f5.6 combo. With a 2x TC you lose 2 stops, so a 300mm f2.8 lens + 2x TC becomes a 600mm f5.6. So to keep the exposure right you have to compensate with either (or both) shutter speed or ISO.
Overall this means that TC's have become more marginal usage items of kit. And as dslr's have improved in quality and picture size, many of the vintage ones have proved to be of insufficient quality. A benchmark test is: if the TC doesn't give you a bit more in the image over simply resizing an image without the TC, then you have to question its use. Browse around online you will find quite a lot of people have done some testing with this benchmark in mind, Bob Atkins for example.
Practical experience is that TC's are of little value on lenses whose IQ is already not great; consumer zooms, cheap old telephoto lenses etc. They work best on quality lenses. They have a mix'n match character - it's worth trying out different ones (generally the 7 element TC's are better than the 4 element ones), and work better on some subjects/photographic situations than on others.
Since most people just have one camera so can't readily switch to more MPx or a smaller sensor camera, overall it's still well worth having a TC if you have appropriate lens(es) to use it with since even the better vintage ones can be acquired so cheaply, it's small to carry and it's a quick and convenient.

[lithedreamer]

This is a tech blurb I wrote for an ad - may offer some insight:

1. Use a camera with more megapixels. More MPx = a bigger image with more latitude to crop.
2. Use a camera with a smaller sensor. Using a lens with a camera with a smaller sensor will result in a narrower field of view. The "crop factor" is a measure of how much narrower compared to 35mm film. Note that ads on ebay describing eg a 500mm lens as "750mm" because most "APSC" sensor cameras have a crop factor of 1.5× are misleading. The focal length of a lens is fixed and doesn't change, can't change. The main change is the field of view. But this is really just "cropping in the camera".
3. Using in camera "digital magnification". This is just cropping and resizing the image and is best done on the PC rather than in the camera.

These digital options have one big advantage over TC's: there is no loss (attenuation) of light, your exposure settings remain the same. With a 1.4x TC you lose approx one stop: so for example a 400mm f4 lens +1.4x TC becomes a 560mm f5.6 combo. With a 2x TC you lose 2 stops, so a 300mm f2.8 lens + 2x TC becomes a 600mm f5.6. So to keep the exposure right you have to compensate with either (or both) shutter speed or ISO.
Overall this means that TC's have become more marginal usage items of kit. And as dslr's have improved in quality and picture size, many of the vintage ones have proved to be of insufficient quality. A benchmark test is: if the TC doesn't give you a bit more in the image over simply resizing an image without the TC, then you have to question its use. Browse around online you will find quite a lot of people have done some testing with this benchmark in mind, Bob Atkins for example.
Practical experience is that TC's are of little value on lenses whose IQ is already not great; consumer zooms, cheap old telephoto lenses etc. They work best on quality lenses. They have a mix'n match character - it's worth trying out different ones (generally the 7 element TC's are better than the 4 element ones), and work better on some subjects/photographic situations than on others.
Since most people just have one camera so can't readily switch to more MPx or a smaller sensor camera, overall it's still well worth having a TC if you have appropriate lens(es) to use it with since even the better vintage ones can be acquired so cheaply, it's small to carry and it's a quick and convenient.

Thanks for this. A few thoughts...

So I have my K-1 (36 MP on 35mm) and my K-30 (16 MP on APS-C), so I could either crop or use the crop body or use crop mode.

One thing that isn't making sense here for me is the idea that you don't lose light when using a crop body. I've watched some of Tony Northrup videos, and he's talked about how when you use full-frame glass on crop bodies you should apply the crop factor to both the focal length and the aperture (my D FA* 70-200 f2.8 becomes a 105-300 f4.2, for example).

That would mean that a teleconverter cuts less light that a crop body, as a 1.4 teleconverter extends the focal length by 1.4 but only cuts the light by 1-stop. I could be misunderstanding this, though.

[biz-engineer]

So I have my K-1 (36 MP on 35mm) and my K-30 (16 MP on APS-C), so I could either crop or use the crop body or use crop mode. One thing that isn't making sense here for me is the idea that you don't lose light when using a crop body. I've watched some of Tony Northrup videos, and he's talked about how when you use full-frame glass on crop bodies you should apply the crop factor to both the focal length and the aperture (my D FA* 70-200 f2.8 becomes a 105-300 f4.2, for example). That would mean that a teleconverter cuts less light that a crop body, as a 1.4 teleconverter extends the focal length by 1.4 but only cuts the light by 1-stop. I could be misunderstanding this, though.

- Regarding the impact of light on image quality, using a TC on FF sensor or using the same lens directly on a crop sensor, using the same exposure parameters would create any significant difference.
- Exception: when shutter speed is not an constraint, i.e lowering shutter speed one stop or more, then the FF IQ is supposed to be superior than the one on crop sensor.
-> TC on FF gives more options.
- Downside (specific to Pentax) is the TC does not fully cover the FF image circle, that should not be. Canon and Nikon TC cover FF image circles.

Example: on the K1 it is now possible to use the electronic shutter. When the lens and camera are on a tripod and the subject motion isn't an issue, it is possible to stop down the lens for maximum sharpness, use low iso, and slow down shutter speed in order to collect more light. I shoot f10, f11 or even f14 , ISO100, shutter speed 1/50 with the DFA150450 and TC on FF, with those conditions, image quality is significantly superior to a crop.

[wissink]

Thanks for this. A few thoughts...

So I have my K-1 (36 MP on 35mm) and my K-30 (16 MP on APS-C), so I could either crop or use the crop body or use crop mode.

One thing that isn't making sense here for me is the idea that you don't lose light when using a crop body. I've watched some of Tony Northrup videos, and he's talked about how when you use full-frame glass on crop bodies you should apply the crop factor to both the focal length and the aperture (my D FA* 70-200 f2.8 becomes a 105-300 f4.2, for example).

That would mean that a teleconverter cuts less light that a crop body, as a 1.4 teleconverter extends the focal length by 1.4 but only cuts the light by 1-stop. I could be misunderstanding this, though.

Interesting. Maybe its a depth of field reference only? Not sure

[lithedreamer]

- Regarding the impact of light on image quality, using a TC on FF sensor or using the same lens directly on a crop sensor, using the same exposure parameters would create any significant difference.
- Exception: when shutter speed is not an constraint, i.e lowering shutter speed one stop or more, then the FF IQ is supposed to be superior than the one on crop sensor.
-> TC on FF gives more options.
- Downside (specific to Pentax) is the TC does not fully cover the FF image circle, that should not be. Canon and Nikon TC cover FF image circles.

Example: on the K1 it is now possible to use the electronic shutter. When the lens and camera are on a tripod and the subject motion isn't an issue, it is possible to stop down the lens for maximum sharpness, use low iso, and slow down shutter speed in order to collect more light. I shoot f10, f11 or even f14 , ISO100, shutter speed 1/50 with the DFA150450 and TC on FF, with those conditions, image quality is significantly superior to a crop.

Hmm... so it isn't really practical for handheld shooting, but could be superior for tripod use, especially with electronic shutter.

Oh, also, what does it mean when you say the TC does not fully cover the FF image circle? With my limited testing with the 70-200, there is no vignetting, so I'm not sure what else I'm missing out on here. I'm disappointed by the lack of sharpness, but it's because of my low shutter speed. I'm not willing to bump the ISO much above 128,000, so it would mostly be limited to tripod use, I suppose.

It was a steal at $389 like-new /w box, case and caps, etc but... :/

[biz-engineer]

Hmm... so it isn't really practical for handheld shooting, but could be superior for tripod use, especially with electronic shutter.

I meant that there is no different between TC on FF or apsc crop, no really that we should use a tripod, but if we do, there is an advantage is using a TC on FF versus no TC on crop sensor.

Oh, also, what does it mean when you say the TC does not fully cover the FF image circle?

The HD TC isn't FF. If you are talking about an old Pentax TC, then, it is FF compatible.

[lithedreamer]

I meant that there is no different between TC on FF or apsc crop, no really that we should use a tripod, but if we do, there is an advantage is using a TC on FF versus no TC on crop sensor.


The HD TC isn't FF. If you are talking about an old Pentax TC, then, it is FF compatible.

Right. I'm using the HD TC on my K-1 in FF mode with the 70-200, and it's not vignetting. So...am I doing something wrong?

[biz-engineer]

I'm disappointed by the lack of sharpness

TC decrease sharpness, but the MTF variation of the lens is the same. i.e stopping down the lens restore sharpness. Example: 70-200 @ f2.8 without TC => become f4 with TC, but if the lens is sharper at f4 , then adding the TC implies that the lens is sharper at f5.6 etc.

---------- Post added 11-11-16 at 21:10 ----------

Right. I'm using the HD TC on my K-1 in FF mode with the 70-200, and it's not vignetting. So...am I doing something wrong?

Maybe... because if you don't force K1 FF mode, the K1 automatically switches to crop mode when the HD TC is mounted.

[marcusBMG]

I've watched some of Tony Northrup videos

AAAAARRRRRGGGG!!!! those TN videos on crop factor are grossly misleading!!

Light intensity is not, repeat not affected by the size of the sensor. F2.8 is still f2.8.
TC's attenuate the light and you lose stops.

[lithedreamer]

TC decrease sharpness, but the MTF variation of the lens is the same. i.e stopping down the lens restore sharpness. Example: 70-200 @ f2.8 without TC => become f4 with TC, but if the lens is sharper at f4 , then adding the TC implies that the lens is sharper at f5.6 etc.

---------- Post added 11-11-16 at 21:10 ----------


Maybe... because if you don't force K1 FF mode, the K1 automatically switches to crop mode when the HD TC is mounted.

I'll have to play with it more. Like I said, I'm sure the K-1 is in FF mode. The camera menu says FF, the quick menu option that lets you choose the focal length says 280mm and is greyed out. Adobe Camera Raw sees them as 36.2 MP files shot with a 70-200 lens @ 280 mm. I'm not sure how this could be wrong.

[Alex645]

There is a lot of theory we could debate for pros and cons, but the proof is in the pudding. With your APS-C and FF, do comparative tests in good light. If youʻre handholding at marginal shutter speeds, do the tests with and without SR.

Theoretically any converter adding more elements and groups and losing light transmission is going to compromise the benefit of 1.4x focal length. The question is, how does, on both the APS-C and FF compare with the TC vs. without the TC but cropped. The TC will need a slower shutter or larger aperture or higher ISO which can also contribute to lower IQ.

If you do this, please post us your image comparison. To me, TCs were more relevant when we were shooting color film and didnʻt have the ease of cropping as we do today.

[lithedreamer]

There is a lot of theory we could debate for pros and cons, but the proof is in the pudding. With your APS-C and FF, do comparative tests in good light. If youʻre handholding at marginal shutter speeds, do the tests with and without SR.

Theoretically any converter adding more elements and groups and losing light transmission is going to compromise the benefit of 1.4x focal length. The question is, how does, on both the APS-C and FF compare with the TC vs. without the TC but cropped. The TC will need a slower shutter or larger aperture or higher ISO which can also contribute to lower IQ.

If you do this, please post us your image comparison. To me, TCs were more relevant when we were shooting color film and didnʻt have the ease of cropping as we do today.

Is there anything you'd like to see in a test? I'm not much for a test charts, but I will take suggestions into consideration.

[Alex645]

Is there anything you'd like to see in a test? I'm not much for a test charts, but I will take suggestions into consideration.

Honestly, Iʻm a wide angle to normal FL photographer. The only test that should matter to you is the kinds of things you would shoot that would require the TC.

Wildlife, sports, the moon or sunsets, compressed city shots? In other words, no point in running a test of the moon at infinity if youʻre hoping to get better shots at the zoo of backlit animals at 15 meters.

[lithedreamer]

Honestly, Iʻm a wide angle to normal FL photographer. The only test that should matter to you is the kinds of things you would shoot that would require the TC.

Wildlife, sports, the moon or sunsets, compressed city shots? In other words, no point in running a test of the moon at infinity if youʻre hoping to get better shots at the zoo of backlit animals at 15 meters.

I'll see if I can't take it out to shoot the moon tonight. Just did a quick informal test of my 100mm Macro with it. No distortion, the overall frame was brightened very subtly by lens corrections in ACR, but otherwise uncorrected. Vignetting was a non-issue, again.