Possible alternative to barlows/teleconverters (1 Viewer)

FernandoBatista · Oct 20, 2010

That spider looks very good, Paul, lots of detail.

You don't know how many diopters does it have, do you? I'm trying to find a 4 or 5 diopter. It would be nice to know if any of these lenses are close to it.

Paul Corfield · Oct 20, 2010

FernandoBatista said:
That spider looks very good, Paul, lots of detail.

You don't know how many diopters does it have, do you? I'm trying to find a 4 or 5 diopter. It would be nice to know if any of these lenses are close to it.

I checked my Miranda lens and it's about 7 diopter.

Paul.

FernandoBatista · Oct 20, 2010

It's close to my Cosina then. I guess it's going to be hard to find a lens like this with less diopters, maybe a 400mm zoom lens, but those don't get so cheap.
Thanks for the info anyway.

Paul Corfield · Oct 21, 2010

My Prakticar 80-200mm arrived yesterday. Took out the front element and the teleconverter section. Very similar performance to the others in terms of magnification and sharpness. The front element made a nice macro lens and it gives a fraction more magnification than the other three I have tried so far.

Last night I won a Tokina 35-200mm SD lens. The SD means that this lens has low dispersion glass in it so hopefully there is some in the teleconverter part. Shall post my findings next week as I'm away over the weekend.

Paul.

Paul Corfield · Oct 24, 2010

Got a chance to play with the Tokina 35-200mm today. For some reason the telenegative group is giving a lot more magnification than any others I've tried. On the scope it's giving me 4.3X magnification (2580mm before crop factor or 4128mm with crop factor) which is a bit of a handful as my tripod is broken at the moment. I can't lock up any of the axis so these were taken with everything loose. I think the lens is sharp enough but I really need a new tripod before I can see how sharp they are with it locked up and with the shutter remote.

Photos are from 30m (98 feet) and they are uncropped.

Paul.

alphan · Oct 25, 2010

Paul Corfield said:
Got a chance to play with the Tokina 35-200mm today. For some reason the telenegative group is giving a lot more magnification than any others I've tried. On the scope it's giving me 4.3X magnification (2580mm before crop factor or 4128mm with crop factor) which is a bit of a handful as my tripod is broken at the moment. I can't lock up any of the axis so these were taken with everything loose. I think the lens is sharp enough but I really need a new tripod before I can see how sharp they are with it locked up and with the shutter remote.

Photos are from 30m (98 feet) and they are uncropped.

Paul.

I think that telenegative are designed for higher magnification to enable it to get the 5.7 X zoom. Normally higher zoom lenses tends to have poorer quality but that may not be true as far as the telenegative is concerned. So those shots are f32 or higher? That would have been my ideal FL LOL. Very well done Paul.

BTW, how does that Tokina rate on it's own and once you got your Tripod fix, check out if the telenegative produce a better result than using a 2+X TC with Macro tube added. One thing for sure, our canon will maintain it's length giving more confidence to birds.

Paul Corfield · Oct 25, 2010

One from this morning of a Blue Tit taken with the Tokina lens. I took a few images of the moon last night and noticed the corners were a little soft so this morning to counteract that I put a macro tube between the camera and the telenegative. This makes the image circle bigger so that soft part of the lens falls beyond the cameras ccd sensor. The downside if you like is that this also increases magnification and on a lens that was already giving 4.3X it has now gone up to around 5X. Took a load of hand held shots this morning and only got a few in focus. It will probably be Christmas before I splash out on a new tripod so I'll have to make do with doing everything hand held for now.

Paul.

alphan · Oct 26, 2010

With such a high magnification, spot on focus would not be easy. But you did it again. That shot was superb even if you shot a ton to get this one.

Paul Corfield · Oct 26, 2010

After some testing I think using a combination of my Antares 1.6X barlow and one of the lower power telenegatives works better than the high power Tokina one. Magnification works out about the same at approx 5X. The Antares barlow is really sharp compared to anything else, it's just a shame it's quite long. With mine I have removed the glass doublet, reversed it and put it back in the chrome barrel. Then I've mounted the chrome barrel inside a macro tube with the glass down near the camera instead of far away as it would normally be. In its normal mounting, the Antares 1.6X actually gives around 2.3X when mounted on the scope and used for photography. With the way I've mounted it the magnification goes down to around 1.5X which is much more usable.

Paul.

alphan · Oct 30, 2010

My Cosina 70-210 finally arrived, took it apart and slot the telenegative perfect fit into an old lens mounting, and into my extension tube. I manage an conversion of X2.4 without any additional macro tube between TC and camera. The results are very good. But with fast failing light, I did not proceed to test with additional macro tube for higher conversion.

Just noticed that my 2"-1.25" reducer are producing so much stray lights which shocked me. But the rear optic housing of my Cosina fit nicely inside that reducer..viola...no more stray lights. That tube got a baffle inside and it only measured 17mm dia. and still no lost of light after testing with and without that tube.

1st pic uncropped and 2nd pic cropped. White Breasted Woodswallow taken from 16m.

Paul Corfield · Oct 30, 2010

Good work alphan. Can you post a photo of the telenegative so I can see if it's similar to any of mine? Some lens makers get branded under various names and use the same parts.

Now you know why I keep boxes full of lens parts. I also use the internal tubes for making baffles and stuff. :t:

Paul.

alphan · Nov 1, 2010

Paul, I did not have a detail shot of the telenegative. I only got one taken hurriedly of the whole thing including my OM mounting from the 2X DOI TC and a baffle I place in front of the mounting as it is chromed. I even forgot to set my WB from daylight.... Did not have my gears with me at the moment so can't do it now. If you need detail pic, let me know.

The rear group will make a good EP. I figure it to be around 20mm FL but when played around with the two groups of element inside, can get higher magnification.

Paul Corfield · Nov 1, 2010

Here's a few images from today taken with the Miranda telenegative. First two photos are with the telenegative mounted direct to the camera and the images are cropped about 50%. Telenegative gives around 2.4X mag.

Third photo was with a 40mm macro tube between camera and telenegative and this photo is uncropped. Distance was 30m (98 feet) for all of them. All taken on the tripod with all axis loose as it's still broken and can't afford a new one just yet.

Really pleased with the performance at this range because at 30m these birds are just tiny specks to the naked eye. Also no visible CA from the Miranda telenegative, even at 100% there is none detectable.

In the next post I shall post some images of how I have it mounted, all completely baffled which greatly enhances the contrast.

Paul.

Paul Corfield · Nov 1, 2010

Some photos showing the finished mounting plus some baffling and one of the telenegative itself.

Paul.

alphan · Nov 2, 2010

Paul, I did mine slightly different from yours LOL. I took out the whole telenegative and it slot perfectly into an old OM lens mounting I took off the DOI TC. No glue or screws to keep in place. It just pop in and stay. That telenegative are made from plastic, so can be squeezed a bit.

Then I slot the two piece into the macro extension tube between the various tubes. I can put more tubes or longer tubes in front to increase the extension tube or like wise the back of the "TC" with macro tube. Very versatile for playing around for various setups. For bthose eager to know more about the telenegative conversion can refer to the attached pictures.

Pic 1 & 2, the two sides of the TC. 3, with the TC slotted onto the extension tube and 4, the end of extension tube screwed in to complete the setup.

Paul Corfield · Nov 2, 2010

Actually mines very mounted very similar to yours alphan and it looks like we arrived at a very similar solution. My Miranda one is all metal and a fair bit bigger than the plastic one you have which is the same as the Vivitar. I've used a chrome bayonet ring similar to you but I had to use it to press down onto my telenegative and the compression fit holds it tightly in place against the bottom of the macro tube. I've got another set of macro tubes for increasing distance behind the teleconverter.

Paul.

thornlv · Nov 2, 2010

Paul, could you further explain baffling, the whys and wherefors and how to.

Paul Corfield · Nov 2, 2010

thornlv said:
Paul, could you further explain baffling, the whys and wherefors and how to.

The light baffle prevents stray light getting to where you don't want it to go, which in turn increases contrast, stops colours getting too washed out, you get better blacks, stronger colour saturation etc. I find the best place to have the baffle is close to the lens, be it a teleconverter, barlow or telenegative. You can flock all the tubes etc with black flock paper but I find using a system of rings near the lens works best and this creates a very dark space where the lens is. I find a ring that has a hole the same size as the lens or slightly smaller works best. With a barlow that has a large diameter glass you can have a hole that's easily half the diameter of the glass and you will retain the same shutter speeds but increase contrast a great deal. For the baffles I use blackened rings and tubes from old lenses but another thing that works quite well are rubber eyecups of old eyepieces. Experiment with before and after pictures and you should see a difference.

Paul.

alphan · Nov 3, 2010

Are there anybody here good with theory regarding light rays, lenses and stuffs like that. As most of us here use the 80mm ED, someone could possibly come out with the light path diagram so that we know where and how big to baffle. The more baffles the better as long as it doesn't obstruct the light path. Without theory, we can only do trail and error.

To test for the need for baffling, darken the room completely with only a bright light coming through the scope. Without the TC or camera mounted, look through the scope and if you see any reflective surface, that must go. If you can see any part of the inside of the tube, it'll give off light refection even if flocked. Only baffling will stop that stray light.

Paul Corfield · Nov 4, 2010

Just won a Tamron Adaptall 2 80-210mm for £3.99 which includes delivery so that will be the next one to test when it arrives. This lens is supposed to have above average optical performance and it's one I've had on my list of ones to try for a while now. Looking at the lens diagram here there's possibly 5 glass elements in the telenegative.

Paul.

Possible alternative to barlows/teleconverters (1 Viewer)

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