[hinman]

Yes, I defy conventional wisdom in testing a 600mm out of a consumer lens that cost me $90. It is bad, maybe not too bad. I was thinking of taking the shots to prepare my Tamron 2x TC with 'A' to marketplace.

Tamron-F TC 2X kR MC4



Tamron 70-300 Di LD + Tamron 2x TC



All test pictures hand-held, I should have done it with a tripod

#1
A 70mm perspective, no TC


#2
A 300mm perspective, no TC


#3
600mm with TC


#4
600mm with TC

Should I keep the TC? Though manual focus, The best thing about this TC comes from the MF part where I can input the correct SR focal length for SR to work accurately in 600mm. I know that the TC is taxing on the speed and lighting. A tripod will help. A better lens would do better, definitely. Many will ask the same question that I have in mind, would cropping do better than the 2x TC, what do you think?

• 600mm is still hand-holdable as all are pretty lightweight
• SR is accurate due to MF with correct input of SR focal length
• Effectively 2 stop loss with 600mm f/11 for the Tamron zoom
• Expects PF/CA as seen in Tamron 1.4x Pz-AF MC4 TC
• Difficult to manual focus, but still feasible
• Expect better sharpness with better prime and use of tripod
• Not usable for shot with movement
• Dirt cheap

---

Last edited by hinman; 08-01-2008 at 10:13 AM.

[hinman]

I find the relevant information in comparing TC's and see how effective 2x TC are in Canon & perhaps Nikno's discussion. It is an old topic revisited. Conventional wisdom is to use 2x TC on a good prime with good speed. And I am not against the conventional wisdom but I think that the Pentax gear has an edge, especially with manual focus TC where I can dial in the correct SR focal length for hand-holding. Of course, if tripod is used, the SR don't help at all.

• TCs - Canon, Tamron and Kenko 2x, 1.4x and 1.5x teleconverters - Bob Atkins Photography
• Teleconverters (Multipliers) - how well do they work?

Thanks,

Hin

[Nesster]

I see the lens, but what are those people doing on it... oh wait, they're there to carry it for you.

[hinman]

I see the lens, but what are those people doing on it... oh wait, they're there to carry it for you.

Nester, thanks for the comment. Sorry to say that I don't quite get your comment.

Though poor quality, my 600mm is very light, why would people carry it for me? Of course, I think the real 600mm with an aperture in f/5.6 ro f/4.0 might have a weight of 15 lb+ and I would see the need in help to carry it.

Thanks,
Hin

[Canada_Rockies]

Nester, thanks for the comment. Sorry to say that I don't quite get your comment.

Though poor quality, my 600mm is very light, why would people carry it for me? Of course, I think the real 600mm with an aperture in f/5.6 ro f/4.0 might have a weight of 15 lb+ and I would see the need in help to carry it.

Thanks,
Hin

Nester was joking about the shot of the ride - the ride was the lens, and the people the carriers. I got it, Nester, but it got lost in the translation, I think. Only we English speakers are that punny.

[hinman]

Nester was joking about the shot of the ride - the ride was the lens, and the people the carriers. I got it, Nester, but it got lost in the translation, I think. Only we English speakers are that punny.

Now that you explains it, I get it. Nester, apology that I am slow to catch the humor.

By the way, how heavy would a true 600mm lens with f/4.0 would weigh? Would a ballpark figure of 15 lb about right? And what would be the average rough weight that one would go about hand holding a tele lens?

I once owned the Vivitar Series 1 70-210mm f/3.5 from Kiron and it weighs 879g (or 1.94lb), and I already had a hard time hand-holding the one touch zoom on the long side. What would be the maximum weight that you would consider feasible to hand-hold for a tele.

Thanks,
Hin

[Canada_Rockies]

Now that you explains it, I get it. Nester, apology that I am slow to catch the humor.

By the way, how heavy would a true 600mm lens with f/4.0 would weigh? Would a ballpark figure of 15 lb about right? And what would be the average rough weight that one would go about hand holding a tele lens?

I once owned the Vivitar Series 1 70-210mm f/3.5 from Kiron and it weighs 879g (or 1.94lb), and I already had a hard time hand-holding the one touch zoom on the long side. What would be the maximum weight that you would consider feasible to hand-hold for a tele.

Thanks,
Hin

The Pentax 600/4 weighs 6 Kg, which is about 13.23 pounds, so your 15 pound guess is pretty close. I find, personally, that as long as I can lift it, a heavier lens is easier to hold long. Probably the weight adds some inertial damping.

[Shashinki]

hehe if you get a 600/4 you're going to spend almost half the cash you spent on the lens later when you find that you need a tripod and head that are strong enough to keep it steady.

[falconeye]

Many will ask the same question that I have in mind, would cropping do better than the 2x TC, what do you think?

So, why didn't you compare a digital 2x upsize (bicubic upsize and sharpening) against the TC images? It will tell you the answer.

But theoretically, a tele lens not producing 1 pixel wide edges (what only the best of best primes do) cannot deliver better resolution when used with a TC. But they can and typically do deliver worse resolution.

Even more theoretically, as soon as a lens becomes diffraction-limited will a TC not be beneficial anymore. Bad lenses are only diffraction-limited at f/8 and below. The best of best tele lenses (all of the f/2.8 type) can already be diffraction-limited at f/4. Good primes are diffraction-limited at about f/5.6 and below.

The diffraction limit for a 2x TC with K20D would have to be 2.5 Microns or f/3.7.

So, a good prime can benefit from a 1.4x TC, only the very best of best primes could benefit from a 2x TC at ~f/3.5; and zoom tele lenses won't benefit from a 2x TC at all.

[hinman]

So, why didn't you compare a digital 2x upsize (bicubic upsize and sharpening) against the TC images? It will tell you the answer.

But theoretically, a tele lens not producing 1 pixel wide edges (what only the best of best primes do) cannot deliver better resolution when used with a TC. But they can and typically do deliver worse resolution.

Even more theoretically, as soon as a lens becomes diffraction-limited will a TC not be beneficial anymore. Bad lenses are only diffraction-limited at f/8 and below. The best of best tele lenses (all of the f/2.8 type) can already be diffraction-limited at f/4. Good primes are diffraction-limited at about f/5.6 and below.

The diffraction limit for a 2x TC with K20D would have to be 2.5 Microns or f/3.7.

So, a good prime can benefit from a 1.4x TC, only the very best of best primes could benefit from a 2x TC at ~f/3.5; and zoom tele lenses won't benefit from a 2x TC at all.

Thanks for the inputs and valuable comments. I may not have the time and experience to do all the pixel peeping and upscaling for comparison. By the way, how do you do the digital 2x upsize (bicubic upsize and sharpening) if you have to do it, what tools would you use to do the resizing for comparison.

What I have done is against the conventional wisdom and push a tele zoom over the limits. I will lose the argument if I push on further. One thing that I like about the combination is that the whole setup for 600mm is still hand-holdable and that SR is fully engaged at the right focal length. But of course, the loss of speed and IQ is a bummer but reality.

Again, thanks for the inputs.
Hin

[falconeye]

how do you do the digital 2x upsize (bicubic upsize and sharpening) [...] What I have done is against the conventional wisdom and push a tele zoom over the limits.

Well. I got a TC myself. They can be useful, esp., as I have said, a 1.4x TC with a good prime. And they are great for image composition and on film.

However, most of the time, a 140% or 200% upscale does the same job. As for tools (shown for 200%/140%):

1. Load the image into the image processing software of your choice (any will do, e.g., Photoshop Elements).
1. Crop to a 50%/71.4% center region within the image.
2. Scale the cropped image to 200%/140%, select "bicubic" as scaling method.
3. Sharpen the image using the "Unsharp Mask" sharpening filter, using, e.g., 100% strength and 1px radius.
Store and compare against an image shot with a 2x/1.4x TC.