Possible alternative to barlows/teleconverters (1 Viewer)

[Paul Corfield]

A photo I took this morning and I stacked my Miranda telenegative with a Praktica one. The Miranda one is nice but the Praktica I didn't find was anything special. When combined though they work well.

This photo is from 30m (98 feet) and the photo is uncropped. Had to use ISO1600 because it's quite dull here today.

This combination on the 600mm Skywatcher 80ED gives 4.7X which translates to 2820mm or for those who like to add crop factor it comes out at 4512mm with the Canon 450D 1.6X crop factor.

Good results I think for the amount of mag but I really need to test CA when the sun is out and also sharpness would be better when I don't have to rely on hand holding the scope.

Paul.

 

[thornlv]

Paul, I wonder, on the back of your comments about each telenegatives IQ (softnes in corners, vignetting, distortion etc) , wether you could build a 'lens profile' with CS5 and camera raw.

?

 

[Paul Corfield]

Paul, I wonder, on the back of your comments about each telenegatives IQ (softnes in corners, vignetting, distortion etc) , wether you could build a 'lens profile' with CS5 and camera raw.

?

I suppose it would be possible. I only have CS2 and Lightroom 2.5 though. ||

In tests with my Sigma and Miranda telenegatives I've not noticed any distortion in the way of barrel or pincushion, no vignetting and CA is no worse than using the scope on its own. The very small (and it is tiny) amount of edge softness can be corrected by putting a thin macro tube between the camera and telenegative, something like a 10mm one does the trick and gives a slight extra increase in mag.

I'm tempted next year to maybe save up for the Baader Zeiss Abbe barlow which gives no loss in image quality and is supposed to be invisible at 2x to 4x. I think that would be the pinnacle of quality for prime focus magnificaton. There's also the much rarer TMB 1.8X barlow which is supposed to be equal to the Zeiss. Next down is the Astro Physics Barcor barlow but the glass element in my Antares 1.6X is supposed to be the same one, polish and multi coatings may be different though. The zoom lens telenegatives are pretty much equal to the Antares I've found. I'll have a few more zoom lenses arriving next week.

Paul.

 

[alphan]

My setup with the Cosina telenegative are not totally free of CA. When shooting totally black birds against bright sky background , the CA can be terrible but that is the extreme scenario.

Paul, Baader Zeiss Abbe barlow at that price could have bought me another scope, how would that perform compared to the better original TCs on the market?

 

[Paul Corfield]

My setup with the Cosina telenegative are not totally free of CA. When shooting totally black birds against bright sky background , the CA can be terrible but that is the extreme scenario.

Paul, Baader Zeiss Abbe barlow at that price could have bought me another scope, how would that perform compared to the better original TCs on the market?

A brand name TC like a Canon or Nikon would be good, maybe slightly better than a Kenko Pro judging by comments on other forums. I would say though that a good zoom lens telenegative probably already surpasses what a teleconverter can produce. If I could find a low power telenegative then I'd sell my 1.4X Kenko Pro and I'll probably be selling my Antares 1.6X barlow too and that would get me more than halfway to the cost of the Zeiss Abbe barlow. Nothing would compare to the Zeiss, it would be the ultimate in medium to high power magnification. Basically, the quality of the image you get at 600mm would (should) be the same at 2400mm.

Paul.

 

[Aegea]

It seems to be very difficult to predict how well a given combination of lens and TC will perform. I have a Tamron 1.4x (same as Kenko AFAIK) and a no-name 1.7x (which actually measures out at about 1.6x). The Tamron is excellent on my Nikon 300 f/4, but is just dreadfully soft on the Orion 80ED, while the 1.7x is mediocre on the Nikon but very good on the Orion. This is not what I expected at all.

 

[Paul Corfield]

It seems to be very difficult to predict how well a given combination of lens and TC will perform. I have a Tamron 1.4x (same as Kenko AFAIK) and a no-name 1.7x (which actually measures out at about 1.6x). The Tamron is excellent on my Nikon 300 f/4, but is just dreadfully soft on the Orion 80ED, while the 1.7x is mediocre on the Nikon but very good on the Orion. This is not what I expected at all.

Maybe the Tamron 1.4X is different than the Kenko 1.4X as my Kenko Pro 1.4X is excellent on the 80ED, very sharp. I've never had a single teleconverter out of around 20 different (7 element) brands that hasn't performed well on the scope.

Paul.

 

[Aegea]

I've never had a single teleconverter out of around 20 different (7 element) brands that hasn't performed well on the scope.

Paul.

Could have been user error, I'll have to try it the Tamron again.

 

[alphan]

A brand name TC like a Canon or Nikon would be good, maybe slightly better than a Kenko Pro judging by comments on other forums. I would say though that a good zoom lens telenegative probably already surpasses what a teleconverter can produce. If I could find a low power telenegative then I'd sell my 1.4X Kenko Pro and I'll probably be selling my Antares 1.6X barlow too and that would get me more than halfway to the cost of the Zeiss Abbe barlow. Nothing would compare to the Zeiss, it would be the ultimate in medium to high power magnification. Basically, the quality of the image you get at 600mm would (should) be the same at 2400mm.

Paul.

The Zeiss Abbe 2X cost 320 Euro before shipping and modifying, The Sony TC cost 350 Euro here and Sigma APO 250 Euro. But if it is that good, then it's worthwhile hunting for it. I do have a Tamron 1.4X (now discontinued) but the quality are poor. Others with manual lenses seems to have some success with it though.

Anybody seen any Zeiss Barlow for sale used? Got to be careful, as quality may not be there anymore thus for sale.

 

[Paul Corfield]

The Zeiss Abbe 2X cost 320 Euro before shipping and modifying.

Anybody seen any Zeiss Barlow for sale used? Got to be careful, as quality may not be there anymore thus for sale.

The Zeiss abbe barlow itself wouldn't require any modifying and it has a built in T-thread for easy mounting. They come up for sale from time to time on astronomy sites, not all that often though.

Paul.

 

[Paul Corfield]

Could have been user error, I'll have to try it the Tamron again.

Which version of the Tamron 1.4X do you have? The older Tamron SP 1.4X had 4 elements in 4 groups and this one is noticeably softer than the Kenko Pro 1.4X when shot side by side. The new Tamron Pro SP 1.4X now has 5 elements in 4 groups which is similar to the Kenko Pro.

Paul.

 

[Aegea]

Paul, I bow to your superior experience. I spent some time last night setting up a test chart and shooting indoors under controlled conditions (my previous judgment was based on initial outdoor "live" shots). All three of the TCs I tested (Tamron 1.4x, "no-name" 1.7x, and Nikon TC-201 showed pretty much identical sharpness. Even the 1.4x and the 1.7x stacked were fine. Looking back at my original photos, the light was worse when I was using the Tamron and my shutter speeds were lower, so I'm inclined to blame camera shake for the softness. (I knew I was going to have to get a better tripod!)

I'm not sure which version of the Tamron I have and I don't have it with me at the moment (at work). I'll take a look this pm and see if I can find out which it is.

Thanks!

 

[Paul Corfield]

This photo was a nearly but not quite. I was photographing something else when this bird landed on my garden fence so I had the wrong shutter speed and had to lighten the image a fair bit which has shown up some noise. Also hand holding the scope on my broken tripod I didn't get it dead on sharp which is a shame. Shows how well the Miranda telenegative captures colours though. Photo uncropped from 10m (32 feet).

I've taken a few of my other telenegatives apart just to see how the elements are arranged. Over the years I've collected a box full of various lens elements and I've managed to put my own 5 element telenegative together and on first look it seem to perform better than these zoom lens ones. Sharpness is the same but it seems flatter to the edge of the field.

Today I took delivery of a Sigma UC 70-210mm lens. The telenegative seems really nice but has been raining all day so I'll try it out tomorrow along with my home made one.

Paul.

 

[Aegea]

Which version of the Tamron 1.4X do you have?

Paul.

It's labeled "TAMRON SP AF TELE-CONVERTER 140F-FNs 1.4X"

It seems to be the same as the Kenko PRO, according to this site:

http://homepages.tig.com.au/~parsog/Guy/testteleconverter.html

John

 

[Paul Corfield]

Some images taken with the Sigma UC 70-210mm telenegative that I got yesterday. All from approx 30m (98 feet) and all three are uncropped.

Paul.

 

[Paul Corfield]

Another image taken with the Sigma UC 70-210mm telenegative. Not bad for sharpness but I find it lacking in contrast and this photo has been edited to get it to this level. Even with a load of baffling I can't get it to perform as good as my Miranda one. It's quite good on magnification though, even with it right up close to the camera it gives around 2.7X mag. Photo is uncropped from around 25m range (82 feet).

Paul.

 

[cango]

Another image taken with the Sigma UC 70-210mm telenegative. Not bad for sharpness but I find it lacking in contrast and this photo has been edited to get it to this level. Even with a load of baffling I can't get it to perform as good as my Miranda one. It's quite good on magnification though, even with it right up close to the camera it gives around 2.7X mag. Photo is uncropped from around 25m range (82 feet).

Paul.

very good considering the distance. nice detail.

 

[Paul Corfield]

very good considering the distance. nice detail.

Yeah, detail isn't bad for the distance. Here's the 100% crop which shows a fair bit of fine feather detail has been captured. All the telenegatives I've tried so far produce the same sort of results.

Paul.

 

[cango]

i would love to see that detail through an olympus E-5. would surely love to have the funds to change my E-3 for one ;-)
I dissected a vivitar 70-210mm for OM I had lying around and extracted 4 pieces/groups, and two of the I assume must be these telenegatives you have been using. Not sure which one is the telenegative. I have tested nr 2 counting from the left. Being a very dull time of year up here, it is hard to get the good light to test them out for real.
Nr 2 is wider at one end than the other. Does it matter? Thanks for any advise.

 

[Musoman]

It's labeled "TAMRON SP AF TELE-CONVERTER 140F-FNs 1.4X"

It seems to be the same as the Kenko PRO, according to this site:

http://homepages.tig.com.au/~parsog/Guy/testteleconverter.html

John

John, did you have to tape the some of the contacts on the teleconverter at all for using on a scope ?