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2X GSO Ed Barlow + 2X DOI teleconverter combo (1 Viewer)
- Thread starter Paul Corfield
- Start date
erniehatt
Well-known member
Paul had a look at making something this morning, cut out a nice fitting circle of timber, will shampher the inside on the lathe later. I tried it in the front of the barlows, it seemed to work ok, but did reduce the amount of light reaching the sensor. Is this normal, or maybe because of the lack of shamphoring. Ernie
Paul Corfield
Well-known member
The light shouldn't drop too much, depends on the size of the hole but if the hole is too big then the contrast isn't as good. I think around a 15mm hole is about right. I tried a load of different sized ones today and the one I posted in the other thread works the best. I went right down to around a 8mm hole but that started to vignette and contrast was only marginally better. With the 2" GSO barlow and a 15mm baffle I guess I only need to drop the shutter speed down by about 1/50sec to what it would have been without the baffle. I think the speed is similar to what I would get with a 2X teleconverter as they also let through less light than a 2X barlow. I'm using the Canon 450D though where I shoot at 800 ISO all the time so the drop in speed isn't really an issue but it may be for your Olympus.
Paul.
Paul.
erniehatt
Well-known member
Thanks Paul, I will give 800 a go though I am not very optimistic about it. Have attached image of the baffle I have made, not to sure how it will go, but cannot see it being to much of a problem. I have found another sauce of reflection, the inside of the Williams extender is shiney, the barrel itself is baffled ok, but if you put a short barrel into it, or like I do pull it in and out to increase the focal length, then the reflections would come into play, I have dulled this down by rubbing some sandpaper around the inside. Ernie
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Paul Corfield
Well-known member
I use the tube that came with the GSO barlow as a 50mm extension tube but the inside of that is shiny also. Like you I just pull in and out to adjust focal length. Yesterday I lined the whole thing from front to back with black material but it had no effect on internal reflections. I think the barlow glass element itself is the main source. Must be something to do with the way light passes through them or the multi coatings need to be better to improve light scatter, probably a combination of both. I read somewhere that the Dakin barlow only has a single antireflection coating rather than a multicoating and this is to reduce what they call "narrow angle light scatter". Apparently multicoatings produce more light scatter than a single layer coatings.
Some barlows have a baffle halfway down the chrome barrel which would put it behind the glass element. I tried this by putting one inside the T-mount and it has an effect on contrast but not to the same level as putting one in front of the element.
Paul.
Some barlows have a baffle halfway down the chrome barrel which would put it behind the glass element. I tried this by putting one inside the T-mount and it has an effect on contrast but not to the same level as putting one in front of the element.
Paul.
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erniehatt
Well-known member
Interesting Paul, I tried out the baffle yesterday and it did seem to make a difference to the images, I didny get that film, that I got before, I am attaching a couple of images, that were taken using ISO 1600 at 1/200sec, they are not perfect there was a 20 - 28 klms per hr wind blowing. I have two of those GSO 2" barlows and they are different, one of them is matt finished the other glossy, so they my have changed them at some stage.In a few days these berries will be ripe, then the will be bombarded with Lorikeets, then I may have something decent to post. Ernie
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Paul Corfield
Well-known member
Wouldn't mind seeing a photo taken with the 2 GSO elements screwed together. Could you do that Ernie?
Cheers,
Paul.
Cheers,
Paul.
Paul Corfield
Well-known member
Cheers Ernie, look forward to the results. It's been something I've thought about trying for a while now.
Paul.
Paul.
erniehatt
Well-known member
Paul I have not forgotten to tyr it, just waiting for the weather to brighten up and to get some decent subjects in those trees. Just won another 2X TC on ebay a Minolta Teleplus, I can't get the appropriate adapters to connect it to the E520, so am in the process of making one, so it will be interesting to see how it goes, also bidding on a 1.7X nikon. Ernie
Paul Corfield
Well-known member
Cheers Ernie.
Minolta to Olympus adapters are quite expensive. What I do in a situation like that is strip the teleconverter down and mount the lens assembly inside either the T-mount or inside a macro tube. That's one reason why I tend to stick to Pentax teleconverters as the adapters are really cheap and the teleconverters are very common compared to other makes.
Paul.
Minolta to Olympus adapters are quite expensive. What I do in a situation like that is strip the teleconverter down and mount the lens assembly inside either the T-mount or inside a macro tube. That's one reason why I tend to stick to Pentax teleconverters as the adapters are really cheap and the teleconverters are very common compared to other makes.
Paul.
erniehatt
Well-known member
Yes Paul I discovered that, but I have made up an adapter for the olympus side, just waiting for one to go from Minolta to T2, then I can try it , weather permitting that is.
I did try the two Barlows today, but the wind was fighting against me and it won as you can see from the image, even at Iso 800 the speed was only 1/30s, hence it's a bit soft. But I think it will work ok. Had a bird or two having a look at the berries, but they are still not quite ripe, but when they are I should have plenty of subject matter.
At one stage you where using extention tubes, but you seem to have gone away from that, was there a particular reason for it.
I am going to try your idea of taking the lens unit fron it's mount, and putting it into the barrel, I am planning a method of doing this at the moment, I am wanting to make evering thing more compact, and reducing some of the weight hanging of the back of the scope.
Last year I had some extended 1.25 barrels made, lookint to have the same in 2" Ernie
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Paul Corfield
Well-known member
The photo looks pretty good Ernie. Is that full frame or a crop?
Regarding extension tubes, I still use them but usually just a 60mm one between the camera and TC. That will take my 1.4X TC up to the same as a 2X one so it's a good solution if that's all the magnification you need and just own the one TC.
Still waiting for my Antares 3X barlow to arrive, been waiting over a month now. Shall have to chase that one up today.
Paul.
Regarding extension tubes, I still use them but usually just a 60mm one between the camera and TC. That will take my 1.4X TC up to the same as a 2X one so it's a good solution if that's all the magnification you need and just own the one TC.
Still waiting for my Antares 3X barlow to arrive, been waiting over a month now. Shall have to chase that one up today.
Paul.
erniehatt
Well-known member
Yes Paul full frame and at about 40meters. I didn't do much to it just a bit of denoising.
Look forward to seeing some results from the 3X. I am looking for something to get me some of the bigger birds ie. pigeons from about 10-12 meters. Ernie
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erniehatt
Well-known member
Paul, tried you little conversion trick, by removing the lens module from the 3X TC and putting it in one of my own making. Reduced the size down from 2 1/4 inches to 9/16 it fits nicely into the T2 to 2" barrel, slide back and forth to add and reduce magnification, had a little accident on the way though, dropped and chipped one of the lenses, luckily I cannot see anf effect in the images. Managed to get one image with it today, not a 100% but getting there, need some practice. I will try this with the other lenses, as it reduces the weight and the distance between Camera and Scope. 45 - 50 meters give or take. Ernie
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erniehatt
Well-known member
Had a little more success yesterday, again not perfect but getting there, this is the best I could achieve under the circunstances, wind blowwing between 34 and 38 Kls/h, Had the bird blowing in and out of the frame as well as focus, had to wait till it reach it's peak and hope for the best, lucky to get this musch of a result. Have discovered that a lot of my problem is these tied old eyes, But I think I may have found a solution. Ernie
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erniehatt
Well-known member
Thanks John, you can say that again, they are active little buggers. Hope you are keeping well. Everyone seems to have deserted this site now adays. Ernie
