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Possible alternative to barlows/teleconverters (1 Viewer)
- Thread starter Paul Corfield
- Start date
Paul Corfield
Well-known member
My Miranda 75-300mm arrived today. It's in mint condition and still in the box, seemed a shame to take it apart but I got stuck in straight away. Used my usual method of sticking a big lump of Blu-Tac to the front element and gave it a good twist. That unscrewed easily and then I used the same method to unscrew the telenegative group. Working like this means it can all be reassembled in the future and nothings been damaged in the removal process.
The telenegative part is in it's own metal housing and the glass has a lovely blue/yellow coating as you move it in the light. On the scope it performs just as well as the Vivitar one I tried last week.
Even though this lens is 300mm the magnification is about the same as the Vivitar 210mm so there was no extra gain from getting a more powerful lens. I'd say the Miranda gives around 2.3X and the Vivitar fractionally less at about 2.2X.
Nice bit of glass and again it's a very cheap way to get a quality teleconverter for using on the scope.
Strong wind here today so no birds around but I photographed this Ladybird from around 12m away. Came out nice and sharp, you can even see all the veins on the leaf.
Paul.
The telenegative part is in it's own metal housing and the glass has a lovely blue/yellow coating as you move it in the light. On the scope it performs just as well as the Vivitar one I tried last week.
Even though this lens is 300mm the magnification is about the same as the Vivitar 210mm so there was no extra gain from getting a more powerful lens. I'd say the Miranda gives around 2.3X and the Vivitar fractionally less at about 2.2X.
Nice bit of glass and again it's a very cheap way to get a quality teleconverter for using on the scope.
Strong wind here today so no birds around but I photographed this Ladybird from around 12m away. Came out nice and sharp, you can even see all the veins on the leaf.
Paul.
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alphan
Well-known member
LOL...of course nothing wrong with the one with TC. But it's nothing better than the one without TC. Without the TC, I can get to have Focus confirm (though seldom use), more lighting or higher SS, less shake (vibration), less sagging on the camera due to another extension, better DOF for more allowance of missed focus during speedy focusing, and when taken, crop to higher magnification (for web use only) but still came out with an as good pic if not better than one taken with TC. The only advantage I see with TC is the closer view during focusing thus allowing better composition. Correct me if I were wrong.
alphan
Well-known member
Yes, the exposure meter play up when used with TC. Don't know why, but with different FL, with and without the Focus confirm chip, will end up with different level of exposure.
alphan
Well-known member
Paul, as usual, your shots always amaze me. Can you run a test. Shoot something not that far away, say 20-30m, but smaller object. Try it using different TCs (DIY, Barlow, telenegative etc) and SW80ED only, crop all of them to show that object only. All taken from the same distant with similar condition. Which one would be better? Luckily UK is a bit far, otherwise you will one day find me knocking on your door wanting more ideas about DIY.
Paul Corfield
Well-known member
This is where experience comes in. There will be a distance where the TC (or any device for high magnification) will start to perform better than cropping, but it's all dependent on the size of the subject. There's so much overlap that I can't say "at this range such and such will be best". Even at 10m a small bird will be better with a 1.4X TC than just the scope.
Paul.
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Paul Corfield
Well-known member
These sorts of tests I've done a lot of in the past so I probably wont do it all again due to the time it takes. I'm self employed and time is money :t:
I know from experience that the lenses I'm taking out of old zooms are the best thing I've tried so far and probably the most exciting advance I've made in the last couple of years.
Paul.
FernandoBatista
Well-known member
Paul, you're getting great results out of those lenses, no doubt.
One question, are these parfocal like a TC? Or do you have to adjust focus when adding it?
One question, are these parfocal like a TC? Or do you have to adjust focus when adding it?
Paul Corfield
Well-known member
I'll have to check. I'm away the weekend so will do it for Monday.
Had a Sigma 75-300mm DL lens arrive today that I got cheap off ebay because the front lens was chipped. The teleneagtive in that works equally as good as the other two lenses I've tried and it provides the same amount of magnification, approx 2.2X. Shall try some low power zooms now just to see if the telenegative is a lower power.
Paul.
alphan
Well-known member
Thanks Paul for the advice. Guess I will just have to go shoot more, both near and far to determine which is better. Frankly, since getting the 80ED, I haven't touch my 200-500 zoom. Went out with a few friends having Sigma 50-500 and 150-500, their shots are nothing compared to mine. I can crop and crop and still maintain the details. That credit mostly went to you for pushing this method. Now you know why I do not want to loose any details with TCs. This had been the best things I ever had with Tele.
Your trying out different optics and lately the zoom telenegative for an totally different purpose make me wish that I had studied harder during school physic class LOL. Thus we can only follow you closely.
Managed to dismantle the Sigma 75-210 zoom, had to butcher it a bit to get the TC element. Jury rigged it with a bayonet end of a ext tube set with some blu tac, took a couple of quick pics - one prime, one with the TC element.Measured the subject and work it out to being approx 2.5 magnification. Dont know about shrpness yet, will need to rig a more robust version and take some 'reaal world' shots.
Also have a bigger element from the lens, this was in front of the TC bit - any idea if this would be useful.
Also have a bigger element from the lens, this was in front of the TC bit - any idea if this would be useful.
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Paul Corfield
Well-known member
There's one of them in my Sigma lens too but I haven't got around to removing it yet. There was a similar one in my Vivitar but it was about three times as long. The Vivitar one makes quite a nice eyepiece, very sharp but the eye relief was poor and I had to have my eye very close to it.
Paul.
Paul.
Paul Corfield
Well-known member
Here's a series I took today from around 60m (197 feet). Took one with just the scope at 600mm as a guide also. Then one with the sigma telenegative, then Sigma stacked with Kenko Pro 1.4X and finally one with Sigma stacked with a 45mm macro tube.
Fernando, the telenegatives aren't parfocal. Two of mine are only about 1/4 turn away from being in focus and the other is about 1 whole turn.
edit - all the images should read 'Sigma telenegative' and not 'Kenko' as I made a mistake on the labelling.
Paul.
Fernando, the telenegatives aren't parfocal. Two of mine are only about 1/4 turn away from being in focus and the other is about 1 whole turn.
edit - all the images should read 'Sigma telenegative' and not 'Kenko' as I made a mistake on the labelling.
Paul.
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Paul, you seem to have mislabelled the examples, ie 'Kenko telenegative' etc. Didnt think about using the front element as an eyepiece, but it makes a cracking loupe.
Also could you explain 'parfocal'
Hopefully going to field test the knock up TCs tomorrow (weather permitting)
Vic.
Also could you explain 'parfocal'
Hopefully going to field test the knock up TCs tomorrow (weather permitting)
Vic.
Paul Corfield
Well-known member
Whoops, thanks for that, yes they should read 'Sigma telenegative' instead of Kenko.
Parfocal means that if you focus the scope on something and then for example put a teleconverter on the camera the image will still be perfectly in focus. Telescope eyepieces often state whether they are parfocal or not so that stargazers can swap and change eyepieces knowing they wont have to refocus the telescope.
Paul.
Parfocal means that if you focus the scope on something and then for example put a teleconverter on the camera the image will still be perfectly in focus. Telescope eyepieces often state whether they are parfocal or not so that stargazers can swap and change eyepieces knowing they wont have to refocus the telescope.
Paul.
Paul Corfield
Well-known member
All were at ISO800
1st test image at 600mm was 1/800sec although probably should have been a bit higher, maybe 1/1000sec would have been better.
2nd image with just the Sigma telenegative was 1/320sec
3rd image with Sigma and Kenko Pro 1.4X TC was 1/200sec
4th image, Sigma with 45mm extension tube also 1/200sec
Paul.
FernandoBatista
Well-known member
Thanks for info, Paul.
I bought a Tokina 80-200, going to try that out too.
More than a loupe, it makes a cracking close up lens for macros
I use the front element of the cosina 100-300 I dismantled for the scope adapter and chip, it’s nearly as good any commercial closeup lens. I’m expecting the Tokina I bough now to behave even better, since it is a much better lens. The cosina 100-300 is not exactly a sharp lens.
Took the Sigma TC element out today to local nature reserve, quite a nice sunny afternoon. also took some test card shots in my back yard, along with the DOI HQ7 TC and My Sigma 150-500 (at 500). quite satisfied with the sharpness - whaat do you think to them
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Paul Corfield
Well-known member
They all look pretty good.
I made another breakthrough today. With the telenegative mounted inside a macro tube I've also included the front objective from the lens I took apart. This reduces the mag from around 2.5X down to 1.7X. I compared photos taken with my Kenko Pro 1.4X and the telenegative ones are razor sharp, easily as good as the Kenko Pro TC. There's zero CA and no distortion. I'll post up some photos tomorrow.
Paul.
I made another breakthrough today. With the telenegative mounted inside a macro tube I've also included the front objective from the lens I took apart. This reduces the mag from around 2.5X down to 1.7X. I compared photos taken with my Kenko Pro 1.4X and the telenegative ones are razor sharp, easily as good as the Kenko Pro TC. There's zero CA and no distortion. I'll post up some photos tomorrow.
Paul.
