Possible alternative to barlows/teleconverters (2 Viewers)

[JvdM]

Comparison between scope and I believe a Takumar 70-200 f/4 objective (looks the same as the one Paul used in post #1).

Provides about 1.95X mag mounted close to camera.

Photo 1 is scope only- ISO 3200 1/500. Photo 2 is with TC- ISO 100 0.4 sec. About 4hrs between photo's account for the difference in light. Range 9m.

 

[JvdM]

Scope plus Takumar 70-200 f/4 evaluated for CA

ISO 3200; 1/3200; range 34m.

I do not think it looks too bad?

 

[Musoman]

Comparison between scope and I believe a Takumar 70-200 f/4 objective (looks the same as the one Paul used in post #1).

Provides about 1.95X mag mounted close to camera.

I think you mean the Takumar 70-200 teleneg ? The objective lens gives a reduction, rather than an increase. Paul has used an objective to take the SW80ED to under 400mm FL, i think

 

[JvdM]

I think you mean the Takumar 70-200 teleneg ? The objective lens gives a reduction, rather than an increase. Paul has used an objective to take the SW80ED to under 400mm FL, i think

Hello Pete

Nice to meet you

No it is the objective with it seems, the TN attached? - looks like a mushroom. I turned it upside down (the narrow end facing forward). Check Paul's post #1 in this section for the illustration.

Regards

Jaco

 

[Musoman]

Hi Jaco

According to Paul , the Teleneg section ( which is below the front objective lens ) is the glass that gives you magnification. This will be the ' mushroom ' shape i think you speak of. The front lens of the Takumar is the Objective lens, and gives a reduction in Focal Length and F ratio, when fitted to the scope.

I have used the Teleneg glass from a zoom lens myself, as a 1.5x TC when mounted very close to the camera. I have not tried using the front Objective lens from a zoom as a reducing lens

 

[JvdM]

Hi Pete

I quickly tried to reconstruct the lens to make sure I am not fooling the crowd. However, this was one of the first lenses I took apart, so the deconstruction was without any finesse. In fact it was so complete I am not even sure from which lens it came or where it fit in the optical chain.

I think I shall just call it "an optical element" - from some lens.

My apologies if I misled anyone.

BTW attached is a photo of said optical element.

Regards

Jaco

 

[Musoman]

If i'm not mistaken Jaco, that looks like the Teleneg section.

If it was the objective, you wouldnt be getting any magnification, only reduction. But there are more skillful scope users here than me who can clarify this for you

 

[alphan]

Jaco, the front most group of lens is the Objective which would be quite big compared to the telenegative which is the group floating inside the middle of the barrel when you zoom.

 

[Paul Corfield]

Hi Pete

I quickly tried to reconstruct the lens to make sure I am not fooling the crowd. However, this was one of the first lenses I took apart, so the deconstruction was without any finesse. In fact it was so complete I am not even sure from which lens it came or where it fit in the optical chain.

I think I shall just call it "an optical element" - from some lens.

My apologies if I misled anyone.

BTW attached is a photo of said optical element.

Regards

Jaco

What you have is the objective with the TN attached which is what you said in an earlier post I think, I only had a quick scan through all the new posts. Pentax seem to make some of their lenses this way, especially their more modern designs and they have all the front bits stuck together as one lump. Still works ok though as I tried a Pentax lens that was the same sort of construction.

Paul.

 

[Musoman]

Would Jaco get higher mag without the Objective on the end of the Teleneg ? Assuming it can be removed

 

[Musoman]

No it is the objective with it seems, the TN attached?

Regards

Jaco

Yes, absolutely right Jaco. I missed that bit, sorry

 

[JvdM]

What you have is the objective with the TN attached which is what you said in an earlier post I think, I only had a quick scan through all the new posts. Pentax seem to make some of their lenses this way, especially their more modern designs and they have all the front bits stuck together as one lump. Still works ok though as I tried a Pentax lens that was the same sort of construction.

Paul.

Hi Paul

Welcome back. We need some more of your sagacious inputs.

This is the 2nd best of the TN's I have salvaged from about 6 lenses. The best is a Vivitar 2X MC Tele Converter (PK mount). Together they give 3.9X focal length extension which is enough - otherwise the view finder looks like the inside of a cow.

Regards

Jaco

 

[JvdM]

Would Jaco get higher mag without the Objective on the end of the Teleneg ? Assuming it can be removed

Hi Pete

The assembly is like one solid piece. I don't think one can dismantle it. Anyway, I am not even going to try. It is mounted and working ok (some CA). I have a Canon FD 35-70 f/4 with similar construction but, either the objective or the TN casts a purple blotch in the centre of the photo. Rather a pity as it held great promise otherwise.

Regards

Jaco

 

[Paul Corfield]

Hi Pete

The assembly is like one solid piece. I don't think one can dismantle it. Anyway, I am not even going to try. It is mounted and working ok (some CA). I have a Canon FD 35-70 f/4 with similar construction but, either the objective or the TN casts a purple blotch in the centre of the photo. Rather a pity as it held great promise otherwise.

Regards

Jaco

The purple blotch in the centre of the photo is down to light scatter. I've found this in the past ith some TN's and it generally takes a lot of inventive internal baffling to get rid of it.

Paul.

 

[Paul Corfield]

Hi Paul

Welcome back. We need some more of your sagacious inputs.

Regards

Jaco

Thanks for the welcome. I've not really been anywhere and still check in about once a week to read the posts. I tend not to use the scope much in the summer months anyway but this year I've been very busy with producing paintings which is my job. That hasn't left me any time to experiment with any new optics. Looking forward to autumn/winter when I use the scope a lot more. Once the leaves are off the trees and the cold, clear air arrives it's much easier to capture good photos.

Paul.

 

[JvdM]

The purple blotch in the centre of the photo is down to light scatter. I've found this in the past ith some TN's and it generally takes a lot of inventive internal baffling to get rid of it.

Paul.

Hi Paul

Thanks for the tip. I shall save it for a rainy day.

re: "a lot of inventive internal baffling" Will 2 baffles do the trick - one to each element or do you need more?

Regards

Jaco

 

[JvdM]

Thanks for the welcome. I've not really been anywhere and still check in about once a week to read the posts. I tend not to use the scope much in the summer months anyway but this year I've been very busy with producing paintings which is my job. That hasn't left me any time to experiment with any new optics. Looking forward to autumn/winter when I use the scope a lot more. Once the leaves are off the trees and the cold, clear air arrives it's much easier to capture good photos.

Paul.

Hi Paul

I have had a look at your paintings. I quite like them. It should be a joy to paint them - yet you call it "work"; then work for us other mere mortals must be called drudgery

I appreciate the value of cold air when using the scope, but down here all the good feathered stuff migrate to Europe during winter. Our cold weather only lasts about 2 months so one has to make do with the warm weather. The secret for warmer climes I believe is to get closer to the critters and lessen the amount of hot air you have to see through. That's also easier said than done, because in some places you drop to the bottom of the food chain the moment you step outside.

Take care.

Jaco

 

[Paul Corfield]

Hi Paul

Thanks for the tip. I shall save it for a rainy day.

re: "a lot of inventive internal baffling" Will 2 baffles do the trick - one to each element or do you need more?

Regards

Jaco

As long as all the internal diameters in the extension tubes are flat black then what I find works best is to keep reducing the diameter of the glass on the TN. I cover the front element of the TN and and make a hole in whatever I use as the blanking piece. The hole can be quite small without seeing any vignetting in the photos, maybe only 1cm in diameter. If you still get a purple blotch in the photo then the particular style of TN you have is probably a lost cause. The method I outlined here I've found works well with TN's and equally well with barlows.

Paul.

 

[Paul Corfield]

Hi Paul

I have had a look at your paintings. I quite like them. It should be a joy to paint them - yet you call it "work"; then work for us other mere mortals must be called drudgery

Jaco

I agree, it's not like work at all and I don't feel like I've done a days work in the 10 years I've been an artist. I can work from 9am till gone midnight which is quite common and I never look at the clock, time just flies by.

Paul.

 

[JvdM]

As long as all the internal diameters in the extension tubes are flat black then what I find works best is to keep reducing the diameter of the glass on the TN. I cover the front element of the TN and and make a hole in whatever I use as the blanking piece. The hole can be quite small without seeing any vignetting in the photos, maybe only 1cm in diameter. If you still get a purple blotch in the photo then the particular style of TN you have is probably a lost cause. The method I outlined here I've found works well with TN's and equally well with barlows.

Paul.

Hmmmm.

Thanks for the input Paul. I am with you on that and will try it your way first.

I also thought that one may have to put a baffle in front of the rear optic as the first element has a very acute curvature (due to it being a 35-70mm). The rear optic also has a larger diameter than those I fished out of other longer focal length zooms, so may need the additional shielding.

Having had a good look at it from front and rear, there is definitely barrel distortion as well (quite normal for this optic I think). As I said, I shall put it away as a "rainy day project".

Jaco