TC Musings

[nirofo]

Originally Posted by Leif

Teleconverters tend to work better with some focal lengths and some lenses than others. I suspect the Canon ones are optimised for use with long lenses, and that the 200mm lens is ill matched. That is consistent with the fantastic results Andy (and others) get with a TC and a 600mm lens. Nikon even had two teleconverters, one for long lenses, and the other for not so long lenses.

I regularly work with a TC14E on my Nikon 500 f4 AFS and can honestly say I can't tell the difference. I'm sure Leif is right, some converters only work well with specific lenses, on the other hand I have a Tamron 1.4 that seems to work well on my Tokina 150-500 f5.6 ATX, my Tokina 80-400 ATX and on my Tamron 90mm Macro. I think if you push the boat out and use a 2X converter on any lens, then you are going to have to except lower quality results. Having said that, if it's the only way you can obtain the shot, then the result is as good as it gets!

nirofo.

[Leif]

Originally Posted by Dave Smith

Thank you for that Leif. I will next test it with my 100-400 lens.

Dave

They also work best on primes, not zooms ... sorry to rain on your parade.

[Dave Smith]

Originally Posted by Leif

They also work best on primes, not zooms ... sorry to rain on your parade.

That's why I tried it on my 200mm lens first.
I've now tried it out with my 100-400 set on 400 and similarly to before the left picture is 400mm alone but enlarged by a factor of 1.4 and resaved. The right picture is 400mm + 1.4x TC, both 100% crops and other than cropping or enlarging unprocessed.

I am now much happier

I've enjoyed doing the tests and have learnt much. I look forward to seeing anyone elses tests.

Dave

[greypoint]

Results using a 1.4x Zuiko with the Olympus [Zuiko] 50-200mm f2.8/3.5 are quite impressive - I'm thinking this might be the one bit of kit I add this year - mind you, they should be good at around £300 new!

[Don Hoey]

As converters will multiply the effect of lack of resolution ( lens softness ) I had intended to do a comparison between 105mm AIS, the 105mm end of 28-105 Nikon zoom, and the 105mm setting on Stevies 28-200 Sigma, as my starter. Weather conditions here have not permitted that.

However I did spot a Hare in the field so did some comparisons using it.

The converter in use is Nikon TC201 2x and this is recommended for lenses of 200mm and below. Prime lenses used are Nikon 200mm f4 AIS and Nikon 400mm f5.6 AIS. These are all designs from the 1980's so are not a reflection of the current range in terms of performance.

I think this shows that although the TC201 is recommended for shorter focal lengths it gives a better performance on the 400.

Images attatched.

1) Full frame at 200mm to put the exercise in perspective.
2) Composite of crops using 200mm, 400mm and 2x converter.
3) Composite of 400mm crops showing the effect of adding sharpening.

Don

[Don Hoey]

I managed an old style test today. No newspaper so I set up an old product leaflet and took the attached pics at a distance of 20 feet.

Lenses used : Nikon 105mm f2.5 AIS, and Sigma 28-200 f3.5-4.5 Ashperical IF zoom. Nikon TC201 2x converter

Lens aperture was f8 for all shots to give the zoom a realistic chance for image quality. Ideally this lens should be at f11 for best performance. Light levels did not allow f11.

Pics attached

1) A crop of the field of view showing the whole target.
2) Composites of 100% crops at 105mm
3) Composites of 100% crops with converter
4) Composites of the Linhof logo at 105mm and with the converter.

Don

[nirofo]

One thing this test does prove is that the old Nikon 105 is still a terrific lens, far better than the new 105 AF. The Sigma doesn't even come close in this test.

The thing I could never understand was, why do you need autofocus on a macro lens?

nirofo.

[Adey Baker]

It certainly shows the value of matching the converter to the lens - the 105 + 2x is very good at F8, though,obviously this makes it F16 in real life. Does the quality hold up at wider apertures, Don?

Now, anybody got a TC301 for Don to see what that 400mm can really do!

[Don Hoey]

Adey,

I thought I would give your mission a go today. Two fresh thought into the melting pot.

1) When deciding a suitable distance last time, I initially tried 14 feet. Without a TC on, my Nikon 28-105 outperformed the fixed 105. Moving to a distance of 20 feet soon sorted that one out. The 105 is therefore happier at 20ft to infinity as at those ranges it outperforms the zoom.

2) I have used the TC for close ups with tubes and 55 micro very successfuly.

In view of the above I therefore decided that for your various aperture test to move the subject out from 20 feet to 35 feet. Composites attatched that show that at that distance the TC performance fell apart. Shed loads of CA at f4 so no point in going wider.

I did the 400 with and without, at 40 feet and the attatched are processed crops. In view of the 105 and distance experience, and as the sun is due to return next week, I will then try the 400 and TC at longer distances.

Pics attatched
1) Todays test target
2) Comparison at 20 feet and 35 feet using 105 plus converter
3) Aperture comparisons at 35 feet using 105mm and converter
4) 400mm at f5.6 at 40 feet - processed crop
5) 400mm and converter at f5.6 and 40 feet - processed crop

Don

[Leif]

Originally Posted by nirofo

One thing this test does prove is that the old Nikon 105 is still a terrific lens, far better than the new 105 AF. The Sigma doesn't even come close in this test.

The thing I could never understand was, why do you need autofocus on a macro lens?

nirofo.

So that users can try auto-focus, find out that it is useless for macro work, and hence not spend ages complaining they wish they'd bought an AF lens? Seriously though, probably because these lenses also make good portrait lenses, and perhaps AF is useful then. (Timid subject runs away but is caught in sharp focus by modern technology.)