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Some digiscoping experiments with a dslr (1 Viewer)

Much has been written on this debate of DSLR versus P&S.

As I see it, the range of the DSLR is limited by weight and price. The 800mm Sigmonster will produce 50X (800x1.6x2) but a complete set-up with camera and tripod will weight in excess of 10 kg and costs 15K$.

The digiscoping setup can reach further and is reasonably priced. It is limited by atmospheric haze and the quality of the optics. IMO good quality very long range photography very difficult.

As far as my photography is concerned, I consider that the practical limit of my DSLR is around 20 meters (18X). Then my digiscoping setup takes over and will effectively reach to about 100 meters (60X). Further than those distances is cheating - sacrificing quality to get distance. Even if I consider I am an experienced photographer, I still find it difficult to produce good quality pictures when digiscoping.

IMO, quality is the big limiting factor in digiscoping. It is difficult to take pictures that compare to the quality produced by a DSLR. Most of the pictures posted on this forum are of very poor quality. Some photographers have outstanding results and their work is top notch - but these are a minority.

As I see it, very long range digiscoping is limited by 5 factors:

1- Light -the more you magnify, the less light you have - low light increases digital noise big time because of high ISO.
2- Stability - the smallest movement, shake or vibration is amplified by your magnification factor.
3- Atmospheric haze and pollution
4- Optics - high magnification optics need a lot of glass and fittings - the more you add, the more you loose.
5- Combine the above 4 and focusing becomes extremely difficult.
 
Ok Paul, you put up a fair argument, What size telephoto are we talking about, it would need to be 600mm to come up to my scope, and at what price, would it compare to a scope. The images above are great images, but they lack detail, different if you are only looking for identification. You say you can get closer, How close, closer that 2.8 meters. I use a 2 inch 2X barlow which gives me good reach.
As Neil says this is an on going difference of opinion, every man to his own.
Of course what Jules has to say is also quite true, but if some photographers have outstanding results, then surely itś the fault of the photographer not the equipment. Ernie
 
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Yep, it's the experimenting that gives me loads of fun. Sometimes good things happen and sometimes bad but you just need to experiment to progress.

Hadn't tried my 17mm Baader Hyperion eyepiece yet so gave it a try just now. No birds around but this is the same tree I took the Magpie photos earlier. This photo was with the 55mm Takumar f1.8 through the Hyperion at approx 100m. Photo is cropped and reduced by around 70% for posting. Pretty good detail I'd say at that range. Not fully sure how to convert it all to mm equivalent.

There's a 85mm f1.8 Asahi Takumar lens that would give some pretty high power. Quite a rare lens though.

Paul.
 

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I have some success using a Swarovski ATS 80HD scope attached to a Canon 400D using a Swarovski TLS800 but I still prefer to use the Nikon 8400
 

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Paul, you are quite correct, the experimenting is where the fun lies, that is why I like digiscoping , there are many challenges, I off course like coming up with new ideas for adapters etc. There is nothing wrong with the results you are getting. Ernie
 
Ernie, if you were only going to work within 30m or less then why digiscope? A dslr with a good telephoto and a 1.4 tc would be all you need.

Hi Paul
I think the reason most people digiscope is because of the cost & the convenience. I personally always carry a scope when birding, so a digicam is no extra hassle. Like Neil says originally digiscoping gave you the extra reach that was`nt being achieved with SLR`s, but now things have changed & DSLR`s can get you out there further. Your last post with the pine cones showed really good resolution for the distance but lacked any decent exposure although i suppose this can be fixed with software. Obviously you like "mucking about" with lenses etc, but i like birding & then trying to get some decent images of said subject. Not really sure where im going with this (it`s getting late!) so i`ll just post a couple of contrasting images & hope they can speak more than words. both pics were taken today, the Gull at c400m range at 50x & the Wheatear at c10m & 20x. Could your setup have got a better pic of the Gull, I expect so but i doubt it would have bettered the Wheatear & i usually try to close the distance between me & subject just to get a better view. Primarily i am a birder. Rob.
p.s. Been having trouble with the Iiceland Gull jpeg i wanted to upload, the forum wouldnt have it so ive put another one on but had to put it through a filter to bring the size down, just as crap but showing more softening. I need that Asahi Takumar lens !
 

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Hi Rob,

Not really sure where I fit into birding. First and foremost I just love playing with optics as you noted. I've got bagfuls of bits, lenses etc in my garage. When I got my first digicam many years ago I was always making little tele lenses to mount on the front or taking photos through my binoculars etc. People say Laurence Poh is the father of digiscoping but I don't subscribe to that. I was digiscoping before I even heard of the term or even knew anyone else was doing it. Beyond that I just like being out in the countryside with the family and while there I'll digiscope the wildlife. Over the years I've got more into birds and they are my number one quarry but it's probably only the last six months or so where I've started to look for birds I've not seen before.

Regarding range, yesterday I took what is probably my longest range photo so I'll post that. I went onto google maps and used the close up satellite view to accurately work out the range and it measured around 315m from where I was stood. The Kestrel was hovering by a pylon so it was easy to gauge where it was in relation to me. For 10m range you can see one of my best ones here http://www.birdforum.net/attachment.php?attachmentid=114886&d=1195915724

Nothing really in it at that range and I guess we would have to be side by side to see how they compare. Most digiscoping set ups should be good at that range though.

Happy birding,
Paul.
 

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Paul, that is a nice Robin shot, I am with you on who started digiscoping, I took pictures through an old telescope with a cine camera in the early 50s while in Korea.
Here are some pics from the FZ50 and williams optics scope.
 

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Still experimenting and this time I'm trying out eyepiece projection with my William Optics DCL-28 (24mm) eyepiece. This works by having no lens on the camera and allowing the image coming through the eyepiece to be projected onto the ccd. By moving the camera further away from the eyepiece using extension tubes you can greatly increase the magnification from the same eyepiece. This method tends to work best with simple Plossl or Orthoscopic eyepieces. Specialized eyepieces with loads of glass in them tend to be made that way because of the way the human eye sees. this isn't needed to get a good image on a camera ccd and an eyepiece with loads of glass doesn't work as well as a simpler design. From what I read you can also get eyepieces designed especially for projection but I've not looked into that yet.

This method I'm trying at the moment is giving me my best photos so far over all ranges. When funds allow I'd like to try some different eyepieces but for now here's some sample pics taken today.

My next expensive experiment will hopefully be with a 2.5X Tele Vue Powermate. With 4 glass elements they are supposed to be very sharp and very well corrected and will be an experiment worth trying. They come in power ranges all the way up to 5X which would be something like 3840mm on my scope.

Paul.
 

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Still experimenting and this time I'm trying out eyepiece projection with my William Optics DCL-28 (24mm) eyepiece. This works by having no lens on the camera and allowing the image coming through the eyepiece to be projected onto the ccd. By moving the camera further away from the eyepiece using extension tubes you can greatly increase the magnification from the same eyepiece. This method tends to work best with simple Plossl or Orthoscopic eyepieces. Specialized eyepieces with loads of glass in them tend to be made that way because of the way the human eye sees. this isn't needed to get a good image on a camera ccd and an eyepiece with loads of glass doesn't work as well as a simpler design. From what I read you can also get eyepieces designed especially for projection but I've not looked into that yet.

This method I'm trying at the moment is giving me my best photos so far over all ranges. When funds allow I'd like to try some different eyepieces but for now here's some sample pics taken today.

My next expensive experiment will hopefully be with a 2.5X Tele Vue Powermate. With 4 glass elements they are supposed to be very sharp and very well corrected and will be an experiment worth trying. They come in power ranges all the way up to 5X which would be something like 3840mm on my scope.

Paul.

Paul, good work on the experiments, The images are very good.
I am not up on this type of projection, so will not make any adverse comments, But one thing I don´t understand, you say that by adding extension tubes you get more magnification, well I have been using this method with the same scope, but of course using a camera lens, I do not gain extra magnification, what I do get, is closer focus distance, which is what normally happens with tubes. I would be interested to see images taken with and without the tubes with all the same settings. Ernie
 
Paul, good work on the experiments, The images are very good.
I am not up on this type of projection, so will not make any adverse comments, But one thing I don´t understand, you say that by adding extension tubes you get more magnification, well I have been using this method with the same scope, but of course using a camera lens, I do not gain extra magnification, what I do get, is closer focus distance, which is what normally happens with tubes. I would be interested to see images taken with and without the tubes with all the same settings. Ernie

I'll do that tomorrow for you Ernie. It's a method that astronomers have used for years for taking photos of planets. Without a lens on the dslr the eyepiece projects it's image straight onto the ccd. As you move the camera further away then it increases the focal length of the scope. The calculation is the distance from the ccd to the eyepiece which on average would be about 100mm for the projection method. The actual calculation based on my 24mm eyepiece goes like this. 100 - 24/24 = 3.17 That gives me a multiplication factor of 3.17 which you multiply by the scopes focal length. In my case it's 480mm x 3.17 = 1522mm on a 35mm camera. Then there's crop factor for dslr's as they have a smaller ccd than the old 35mm slr's. So multiply 1522 x 1.6 = 2435mm. If I was to use say a 50mm lens on the camera looking through the same eyepiece it would only give me a 1600mm lens. By using no lens on the camera I have added 835mm plus I can vary that my moving the camera nearer of further away. Image quality depends on the eyepiece though and that's something I shall experiment with some more. It's all good fun. :t:

Paul.
 
Paul, after a bit of searching, I can agree with the formula you give, except for the 1.6 crop factor, nowhere have I seen this added to the equation. The only reference I have found on this concerns when you are using old 35mm lens on digital cameras, surely this would not come into it as you are not using a lens, I don´t think the scope focal length is based on 35mm. I am not sure of this only what I have read. I don´t own a DSLR. Ernie
 
Paul, after a bit of searching, I can agree with the formula you give, except for the 1.6 crop factor, nowhere have I seen this added to the equation. The only reference I have found on this concerns when you are using old 35mm lens on digital cameras, surely this would not come into it as you are not using a lens, I don´t think the scope focal length is based on 35mm. I am not sure of this only what I have read. I don´t own a DSLR. Ernie

It's not so much to do with the actual lens. It's the size of the film plane that's different between 35mm slr's and dslr's. The ccd in digital slr's is smaller than 35mm film. The film plane of a 35mm slr captures a bigger image than the ccd of a dslr which makes the photo on a dslr appear to be magnified. I have seen this crop factor applied to telescopes as well in the past so I think it is correct.

Paul.
 
It's not so much to do with the actual lens. It's the size of the film plane that's different between 35mm slr's and dslr's. The ccd in digital slr's is smaller than 35mm film. The film plane of a 35mm slr captures a bigger image than the ccd of a dslr which makes the photo on a dslr appear to be magnified. I have seen this crop factor applied to telescopes as well in the past so I think it is correct.

Paul.

Paul, I hope you don´t think I am questioning your word, itś only because I am unsure, and like to get facts correct, I will accept your findings. Ernie
 
Paul, I hope you don´t think I am questioning your word, itś only because I am unsure, and like to get facts correct, I will accept your findings. Ernie

No problems Ernie. It's good to ask questions. I spent some more time browsing the web and as far as I can see it's correct to multiply by the crop factor of a particular dslr to get the 35mm equivalent as 35mm is considered the industry standard. With some dslr cameras it's 1.5X, others it's 1.6X and some like Olympus it's 2X. A smaller ccd sensor just sees a smaller section of the image. For a 35mm film camera to take that same smaller area of the photo it would need to zoom in by that amount. The dslr doesn't provide any extra magnification by having a smaller ccd, it's just the illusion that it does.

It's the same reason why a lot of astro photographers use web cams to take photos of the planets like Jupiter, Mars and Saturn. A web cam has a tiny ccd, just a few mm across but because of the crop factor the apparent image seems to be magnified by a huge amount. I've adapted my own webcam to do the same thing. I removed the lens of the webcam and fixed on a 1.25" chrome barrel so that it goes in the eyepiece holder of the scope. I've pointed the scope at targets in daylight and targets that appear tiny at a long range come up huge when viewed on the screen. A single photo is poor quality but astro photos are taken by stacking a few hundred photos on top of each other with a degree of transparency and over that many photos the details are resolved.

Paul.
 
Thanks Paul, that explains a lot, and I understand the stacking of inages, as I do a similar thing in photoshop with some of my images. Ernie
 
Here's an example I've done today showing how eyepiece projection works. For this example I've used my 2X teleconverter but it will work for anything from eyepieces, barlows to teleconverters etc. All the principle involves is increasing the distance between the camera and the eyepiece by using some sort of extension tube. It's easy with a teleconverter as the extension tubes already have the correct bayonet fittings and they are usually blackened and baffled to stop stray light.

Instead of this method you could stack barlows or teleconverters together or you could use a more powerful eyepiece. The only problem there is the amount of light you lose compared to this method where the light lost is much less and shutter speed is affected very little.

The first image in the series below was taken using a 76mm extension tube, the 2nd image was with a 50mm tube, the 3rd was with a 26mm tube and the last photo was taken with just the teleconverter and no extension tube. It was early morning, dull and cloudy so I shot this series at ISO800.

Paul.
 

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Paul that difference shows up very well, but say you are using just extension tubes, how much difference would it make, and how far can you open up the distance between CCD and eyepiece. Ernie
 
Paul that difference shows up very well, but say you are using just extension tubes, how much difference would it make, and how far can you open up the distance between CCD and eyepiece. Ernie

You wouldn't be able to use just the extension tubes on their own as there needs to be some sort of eyepiece/barlow/teleconverter between the objective lens and the camera for it to work. The way I had it set up was in this order : camera + extension tubes + 2X teleconverter mounted to the scope. The changes in magnification were made by altering the distance between the camera and the 2X teleconverter using the different extension tubes. I suppose there's a limit as to how many extension tubes you could use. I could probably add another 50mm before I ran out of focus to reach infinity. Also, the more extension tubes you add then the closer you can focus. With the 76mm tube I can focus down to around 6 feet.

If I was using an eyepiece instead of the teleconverter then the magnification would depend on the eyepiece being used. For me the teleconverter produces the brightest image when compared to a similar eyepiece and it's easy to set up with the camera because of the bayonet mounts. With an eyepiece it's harder to make adapters and you need an erecting prism. With the teleconverter on this type of astro scope you don't need an erecting prism, the image is already the correct way up in the camera. Just waiting for some sunny weather now to try it all out properly. Even with todays dull weather it was pretty good out to 100m. A good filter like the William Optics VR-1 or the V-Block anti-fringing filter will also make a big improvement to the photos and increase sharpness,contrast and resolution. About £40 here in the UK so that will have to wait. getting close to a set up that I'm really happy with now.

Paul.
 
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Also, the more extension tubes you add then the closer you can focus. With the 76mm tube I can focus down to around 6 feet.

Paul now this is exactly what I was referring to earlier, I do the same thing by extending the barrels of the eyepieces so far my minimum is between 7 and 8 feet.
Maybe I misread your earlier post as I assumed you were speaking of using no lens only the eyepiece. Keep the experiments coming. Ernie
 
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