Possible alternative to barlows/teleconverters (2 Viewers)

[Paul Corfield]

here is a picture of the pieces... so I suspect it should be in the middle section.

closest to cam is 1glass and infront two elements...

to me it doesnot seem like any are biconcave

In that photo you probably just need the part with the shorter legs. I've had ones like that before and I'm not a fan of them. The better ones are the single piece designs that just screw in and don't have those annoying legs on.

Hold the TN about 30cm in front of your eye and look through it. The image should be the correct way up. Chuck out any of the lens groups where the image is inverted.

Paul.

 

[kurakura]

short legs are inverted... long legs is giving 3xmag, but not biconcave... in the first section close to the cam there was a biconcave lens that gives roughly 1,5-1,6xmag

 

[kurakura]

with the lens connector mounted the iris give some vignette even wide open... had my hopes up

 

[Paul Corfield]

The iris needs to be quite a way down the tube to stop the vignetting. A lens cap with a small hole on the front objective works better.

Paul.

 

[Paul Corfield]

Won a Sunagor 75-300mm lens on ebay for the tiny sum on £1 on ebay last night. Shall post photos taken with the TN when it arrives.

Paul.

 

[Paul Corfield]

My Sunagor 75-300mm lens arrived yesterday. It has the type of TN's that require nearly a whole strip down of the main parts of the lens to get at them. The TN's are the two part interlocking type that move away from each other when the lens is zoomed in and out. The front TN is quite strong at around 3X mag or more. Combining it with the rear TN reduces this to somewhere between 1.5X and 2X but mounting the two units is a bit harder than a regular TN.

This Robin had just taken a bath so the feathers are fluffed up nicely. This was taken with the 2 TN's interlocked. Uncropped from around 8.5m range.

Paul.

 

[Tord]

I tried the Teleplus 2X macro teleconverter the past weekend. The drawback is that it is a quite big and heavy lump that changes the setup balance substantially, more than my 150mm Arca-Swiss rail can compensate for. Near and far focus ability was also impacted quite a lot so I need to re-think.

Results? Will have to wait until I have resolved the issues.

I went back to square one and re-thinked from scratch. Provided you accept limitations in close focusing range, the Teleplus 2X can be used without any extension tube on the TLAPO804 thanks to the improved Crayford focuser that has a long play. The nice thing with the Teleplus 2X design is the helical focuser allows for a few extra cm extraction so the closest focus range is something like 12-13 m. To reduce the amount of connecting components I purchased a cheap OM T-ring 2" adapter and OM-m4/3 adapter. The balance issues are virtually gone and there is not much play to speak of.

So now I can turn my scope into a quite compact and portable setup ~1000mm F/12. Tried the setup yesterday from the car and at a first glance results look quite promising. Will post photos later for you to judge.

 

[Paul Corfield]

I went back to square one and re-thinked from scratch. Provided you accept limitations in close focusing range, the Teleplus 2X can be used without any extension tube on the TLAPO804 thanks to the improved Crayford focuser that has a long play. The nice thing with the Teleplus 2X design is the helical focuser allows for a few extra cm extraction so the closest focus range is something like 12-13 m. To reduce the amount of connecting components I purchased a cheap OM T-ring 2" adapter and OM-m4/3 adapter. The balance issues are virtually gone and there is not much play to speak of.

So now I can turn my scope into a quite compact and portable setup ~1000mm F/12. Tried the setup yesterday from the car and at a first glance results look quite promising. Will post photos later for you to judge.

I stripped down one of my Teleplus 2X macro focusing TC's last night so that I can have the option of a helical focuser without any additional magnification. The other one I shall keep as it is.

Paul.

 

[Paul Corfield]

Mounted an Olympus Zuiko 100-200mm TN inside my empty Teleplus Macro Teleconverter housing today. It's a perfect fit into the chrome bayonet ring on the back of the TC. Gives around 1.6X mag. Good little TN in that Olympus lens.

Paul.

 

[DanC.Licks]

Yes, that looks good. Don't see any CA at all.

 

[JBT]

Wow! You guys are getting some great results with these. How important is alignment when doing this? Does the TN need to perfectly aligned with the scope and camera to achieve the best image possible or can it be off centered a bit? Also for those who have experience doing this how do these TN compare to a good barlow? Are the results from using these TNs just good for the money or are they actually as good or even better than using a high quality barlow like a Tele Vue or something similar? Thanks.

 

[DanC.Licks]

I myself have not hade very good luck with a Barlow, but I only have a Celestron Ultima 2x. Maybe Paul can tell you more.

 

[Paul Corfield]

Essentially the TN is very similar in design to a barlow. Some TN's are two element and some are 3 element and they compare to 2 and 3 element barlows in design. I think the glass in a TN is better quality than a barlow equivalent. The TN's have very good blackened edges and very good multi coatings. The three element designs don't introduce any extra CA either. By comparison, a barlow gives very poor contrast and photos are usually quite washed out. There are ways around that by making special baffles to improve stray light etc. A TN is designed for photography while a barlow is designed to be used in the black of night. Barlows don't handle daylight too well.

TN's can also be mounted onto an eyepiece and be used just like a regular barlow for star gazing etc.

Powermates are a slightly different design to either TN's or barlows being that they are 4 elements. Apart from that, a TN is equal to it as far as photography goes.

Alignment of the TN isn't too critical, I only get mine on center by eye but it can be off by a little bit and still give good results. Sometimes I find something that they fit into almost perfectly and then alignment isn't an issue.

Paul.

 

[JBT]

Thanks guys! Looks like I'll have to give it a go.

 

[JBT]

Got a Canon FD 100-200 but having trouble getting the TN out. Tried the Blue-Tac technique with no luck. Anyone here been able to successfully remove the TN from this lens?

 

[Paul Corfield]

Which version do you have? The 100-200mm had at least two, maybe three different styles of TN depending on the lens coatings. I posted a couple of photos below showing the two common types of TN. You had the basic 100-200mm, then one with S.C. in white letters around the front of the lens where you screw on filters and another with S.S.C. in red letters. The S.C. was the Canon spectra coating and S.S.C. was the super spectra coating. The regular and the S.C. had different TN's, not sure if I have ever seen an S.S.C. though.

I've posted a couple of images and you probably have one of these variants. If it's the one with the 4 holes then what I do is use a pair of needle nose pliers that taper to a small point on the pliers jaws. Spread the jaws apart, insert into the holes and unscrew the TN. If the pliers don't go to a fine enough point then grind them down to the right size. If you don't have a bench grinder then metal sanding paper can work but it will take a while. If you have the other TN design and it wont move then it will require much more stripping down of the lens to get a better grip on the TN. Keep trying with the Blu-Tac, use as big a lump as possible to get the most leverage. If that still wont move it then it will take maybe 20 minutes to strip the lens down. Use a sharp knife to cut through the rubber grip and start undoing all the little screws. It's a good idea to strip lenses right down to the bare bones anyway. Some of the blackened tubes make good baffles to use later on. Usually a TN will not produce the best contrast on its own so it will need some baffles to get the contrast better in the photos. Sometimes also you may see a bright spot in the photo which is orange or purple in colour. Try mounting the TN in reverse and it can get rid of this. It has no effect on sharpness etc.

I've never had a TN yet that I couldn't get out and I've stripped down loads of lenses now. Probably 80% come out with Blu-Tac, use a really big lump to get the most leverage possible. Some require a strip down of the lens but that just because of their design.

The big front element from the lens will make a good macro lens. Put something like a 50mm lens on the camera and hold the extra lens from the 100-200 on the front of it. It will let you get in really close for closeup macro photos. You can glue the lens to an old filter ring to make it into some you can use easier.

The front elements also make good focal reducers for the scope. Some of the smaller diameter ones can be mounted into macro tubes. Used on the scope they will take it down from say 600mm to about 360mm. They are all quite good in the middle for sharpness but some can be a little softer towards the edges. I have an old 75-300mm Miranda that is sharp the whole way across.

The lens behind the TN usually is very good as a hand held magnifier. Hold it up close to your eye and then go up really close to anything you want to study in detail.

Paul.

 

[DanC.Licks]

I picked up a Canon 1.4x Extender III yesterday to use on the road with my Canon EF 400/5.6 L USM on my E-M1. This morning I tested it against my Canon 100-200 TN on my 90/600 triplet.
Well.... The Extender is definitely better, especially when you get further away from the center, but it is not THAT much better, and it cost me €350.- where my TN cost me about €35.- including the original Nikon extension tube I put it in. Here, see for yourselves:



The Ext III is great on the 400 though!

 

[Paul Corfield]

I'd imagine with the better 3 element TN's that you wouldn't see any difference at all. Which version of the Canon TN do you have in my photos that I posted. Pretty sure one or both are just simple doublet designs.

Paul.

 

[DanC.Licks]

The non S.C. one on the right is just like mine. Seems to be a two element.

 

[Paul Corfield]

What sort of range are you at for the bank notes? Haven't taken any bank note photos for a few years. Shall have to try some with all the new lenses I have.

Paul.