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ZEISS DTI thermal imaging cameras. For more discoveries at night, and during the day.

Possible alternative to barlows/teleconverters (1 Viewer)

Playing around with the lens elements from the Vivitar 75-205mm macro that I've started breaking down. I have removed two sliders so far. This is a test of the glass from the first slider (nearest the objective lens). When removed from the slider (too big to fit into my macro tubes) I found two glass elements separated by a thin metal spacer ring. They were about the right size to just push to the back of my t-adapter and secure with a small retaining clip. They are as close to the camera as I can get. It looks like these elements give at least 2-2.5x magnification. The image is sharp and no apparent CA. Two quick shots adjusted for levels and resized for posting (uncropped and unsharpened). Looks as good as what I get with my GSO 2X barlow. The wren was moving around quickly and so focus may not be tack on. Also, my flocking came loose and that's causing the bright areas in the photo...but good enough for a first take on these elements. I've removed the element from the second slider (probably the teleneg), but it's much smaller and have to find something to mount it in for testing.

Rick
 

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Paul Corfield said:
What I decided to do this afternoon was stack the new Minolta telenegative with the Sunagor one, seeing as they are both the same level of sharpness, which is pretty sharp. Stacking them together gives 2.5X magnification but this will go up if you move them further apart. Sharpness is still excellent to the point where I can't really fault the results. Not bad for two lenses that only cost me around £10 total.

First photo from 33 feet and second photo from 115 feet, both uncropped.

Paul.
Click to expand...

The two TNs stacked seems to produce better IQ than a single 2.5X TN. :-O
 
alphan said:
The two TNs stacked seems to produce better IQ than a single 2.5X TN. :-O
Click to expand...

I agree, and that's what I've found to be the case so far. I compared the two stacked with my best 2.5X teleneg yesterday and the two stacked ones were better. I have the Sunagor mounted so that I can just slide it in and out from the rear of my T-ring. Today I'll set the smaller Minolta one into a tube that can go inside the front of the 2" T-mount adapter and that shall give me a very neat and compact way of going from 600mm to 1500mm, all without altering the length of the setup.

Paul.
 
To contribute a little to the topic, I’ve been trying my two negative elements today, one from a Nikkor 80-200 F4 AiS and another from a Tokina 80-200 F4 AiS. Each of the negative cells gives me about 2.1x magnification, so I tried stripping them down further as each of these negative cells have three negative elements inside stacked together.
Having removed one of the elements, the other two cannot be removed as they are cemented, I got a 1.4x (Nikkor) and a 1.5x (Tokina) negatives, apart from that they’re very similar to each other. They’re quite sharp in the middle with the Nikkor having a slight edge, but they’re as soft as melted butter in the corners. I mean soft, not curvature, they’re actually extremely flat across the field with the TL APO, but of centre resolution drops dramatically. Also there’s a good bit of CA introduced, I guess that third element was there for a reason |:p|
 
If you want a low power one that is also flat/sharp across the field then go for a lens that starts at 100mm. Hopefully my Prinzflex 100-200mm will be here tomorrow although being a budget lens I'm not expecting too much.

Paul.
 
Yes, seeing your tests that’s the way I’d go, but since I already had those at home for some time I still gave it a try. Also I’d prefer a 1.4x instead of a 1.6x.
BTW does the sunagor correct the curvature in anyway or is it neutral?
 
FernandoBatista said:
They’re quite sharp in the middle with the Nikkor having a slight edge, but they’re as soft as melted butter in the corners. I mean soft, not curvature, they’re actually extremely flat across the field with the TL APO, but of centre resolution drops dramatically. |:p|
Click to expand...

Did you tried reversing it (front to back or vice versa)?
 
The Prinzflex 100-200mm lens arrived today. Another good little lens and the telenegative performed well, as good as the other 100-200mm lenses which was surprising as it's a budget make. I've seen the exact same lens under other names which so far are 'Mirage' and 'Sunasor', not to be confused with Sunagor unless the ebay listing was a spelling mistake. The Prinzflex telenegative housings are different to the Sunagor so it's possible Sunasor was a separate make to Sunagor. Magnification with the Prinzflex is around 1.5X

Paul.
 
Here's three images taken with the Prinzflex 100-200mm telenegative. Range was around 10m (33 feet) for the first two and 5m for the last one.

Paul.
 

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One more with the Prinzflex 100-200mm. Only from around 4m range, uncropped. This female Blackbird has been nest building now in my garden for a few days and isn't bothered at all about me being in the garden. She happily gathers moss and twigs just a few feet from me. I think it's the same bird as we had last year as she's building the nest in the exact same spot.

Paul.
 

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Do you know if you've limted your long distance focusing by using that amount of tubing?

I remember trying this myself a long while back, and i noticed a slight drooping of the focus tube, the ext tubes and the camera when racked right out for close focus, with such a length. Mind you, i think i had a battery pack mounted as well.
 
Musoman said:
Do you know if you've limted your long distance focusing by using that amount of tubing?

I remember trying this myself a long while back, and i noticed a slight drooping of the focus tube, the ext tubes and the camera when racked right out for close focus, with such a length. Mind you, i think i had a battery pack mounted as well.
Click to expand...

I rarely leave the camera in the back of the scope unsupported and when I do put it in the scope then it's always supported by my hand. I rarely even ever tighten any of the locking screws and just poke the camera in to take a photo and pull it straight out when finished.

Long distance focusing goes down to about 30m with that much extension but I split the extension between the scope and the camera. About 75mm of extension is on the scope and the rest is on the camera via macro tubes. To regain the far focusing all I do is remove the extension tube from the scope. Before I start a photography session I check how far each method can focus just to be sure whether the extension needs to be in the scope or not.

Paul.
 
My China made extension tube will not be able to hold steady to the T-2 adapter that I need to pack steel wires behind the mounting locks to hold it tight. And I always have the camera strap and a strap for the scope around the tripod head, just in case any part of the extension give way and drop to the ground.

I always keep my total extension tube to 80mm only which will give me about 5m close focus and infinity. Anything closer with longer extension tube would take me ages to rack out, unless the bird are accustomed to human and will pose patiently. Maybe one day I should try it with a hide in my garden. White breasted Waterhen would come to within 4 m but then I can just shoot with my 75-300.
 
Got a Canon FD 80-200mm lens the other day from ebay. It had the rear end and the objective missing which was ok as it meant I got it really cheap, just £1.99.

It's got a nice telenegative and quite flat almost to the corners. Spacing it away slightly from the camera insures that any corner softness is removed as that part of the image circle will then fall beyond the camera sensor. Mag is around 2X although I need to check exactly.

Here's a couple of 10m range (33 feet) and they are both uncropped.

Paul.
 

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