Lens advice for Canon 550D on Vortex Razor HD (1 Viewer)

BodyResults · Oct 2, 2012

I just got the Vortex Razor 20-60x85 HD Spotting Scope and have a Canon 550D that I thought I might use for digiscoping. I have never digiscoped before but do a lot of long lens bird photography.

I've ordered the digiscoping attachment that will allow me to connect the camera lens via the filter threads.

Now I'm wondering what type of lens is recommended for this? I have some fast primes like 50mm f1.4, 85mm f1.8 but also have some zooms.

What's the recommendation of a lens for this type of setup?

Thanks
Doug

bluedubius · Oct 4, 2012

I've always had good results with mine using a Nikon D40 and a Nikkor 50mm f/1.8. You need not worry about "fast" primes because the system is limited with respect to light by the scope and not the camera lens. So, you won't gain any additional advantage by using something like the 50mm f/1.4. May not hurt anything either, just a bit heavier than a slower lens. Are you using the Vortex DCA for attachment?

grumps · Oct 4, 2012

Just wondering what is the best set up? Using a 50mm lens or just attaching the camera body?

Hugh

BodyResults · Oct 4, 2012

Thanks for the response Rick.

Yes, I'm using the Vortex DCA. I just got it last night. I hooked it up and it seems to connect very nicely.

I'm puzzled by your response to about using a fast prime. It is almost like you are implying aperture doesn't matter. If I used a lens with max Ap of 5.6 I would get only 1/8 of the light compared to the 1.4 ap lens.

With the kind of focal length we are talking about on the scope I want to get as fast of a shutter speed as possible.

In a quick test last night I think having a bigger aperture will help. I'll do some more testing to see what focal length might be best.

bluedubius · Oct 4, 2012

Definitely using the scope eyepiece and a lens on the camera.

Paul Corfield · Oct 4, 2012

BodyResults said:
I'm puzzled by your response to about using a fast prime. It is almost like you are implying aperture doesn't matter. If I used a lens with max Ap of 5.6 I would get only 1/8 of the light compared to the 1.4 ap lens.

You can go up to around f11 before noticing any change in shutter speed, that's just the way primes work in digiscoping set ups. I think it's to do with the way the light exits the eyepiece.

Paul.

BodyResults · Oct 4, 2012

Paul Corfield said:
You can go up to around f11 before noticing any change in shutter speed, that's just the way primes work in digiscoping set ups. I think it's to do with the way the light exits the eyepiece.

Paul.

Interesting Paul. I'll spend some time testing this weekend.

In my quick indoors test last night I focus the scope on a computer screen about 30 feet away. If I recall correctly I used live view, f1.4 and ISO 6400. At full zoom on the Vortex to 60mm shutter speed was at about 1/25 ss. Then by zooming out on the vortex I was at about 1/200 ss.

I think at first I tried f2.0. When I went to f1.4 SS doubled as I would have expected.

Doug

SteveClifton · Oct 4, 2012

BodyResults said:
Interesting Paul. I'll spend some time testing this weekend.

In my quick indoors test last night I focus the scope on a computer screen about 30 feet away. If I recall correctly I used live view, f1.4 and ISO 6400. At full zoom on the Vortex to 60mm shutter speed was at about 1/25 ss. Then by zooming out on the vortex I was at about 1/200 ss.

I think at first I tried f2.0. When I went to f1.4 SS doubled as I would have expected.

Doug

Doug, like you I also find the theory doesn't hold up in practice, and also see an increase in SS when opening the aperture to its widest.

As for lenses to try with the 550D, I have had some success with both the 18-55 IS, 40mm 2.8 pancake, and also the 50 1.8 mark I.

The kit zoom works better than expected, though I prefer the shorter 40mm as it reduces the centre of gravity on an already back-heavy set-up.

I find with all of these (especially the 50mm as I remember) I needed to use an EV compensation of around minus 1-1.5 stops, or even more in bright light to get an acceptable exposure. Results can be quite good though obviously you need to use either the self timer or a cable/remote release to trip the shutter. Also, if it's at all windy, forget it! Video is especially successfull using this method. If you absolutely need to get a record shot at huge distance using video mode, then the x7 move crop mode provides a huge amount of magnification when the scope is zoomed to 60x!!

btw, I should add that I use the Swarovski DCA (don't know the Vortex DCA, but I assume it is similar?), however I would never dream of hanging my camera on the plastic filter threads on modern lens. Instead I rigged up a platform type adapter on which the camera can be mounted, allowing a gap of 1-2mm between the camera lens and scope eyepiece. This allows the use of live view AF for fine tuning focus once you get close using the scope's focusser.
If you have a legacy lens with metal threads that can be made to work, then that should work better in terms of a direct attachment to the DCA, but as you probably know, this is not an exact science!

Cheers

Steve

BodyResults · Oct 4, 2012

Thanks for the response Steve. It's great to hear about the lenses you have tried.

I looked at a video of the Swarovski DCA. The Vortex DCA is almost identical.

I do think it would be nice to have a small platform that supported the camera and lens weight so the are not creating so much of a level. I did try using live view and adjusting focus and that worked fine indoors. I can see in any sort of wind this would not work well.

Thanks

SteveClifton · Oct 4, 2012

BodyResults said:
Thanks for the response Steve. It's great to hear about the lenses you have tried.

I looked at a video of the Swarovski DCA. The Vortex DCA is almost identical.

I do think it would be nice to have a small platform that supported the camera and lens weight so the are not creating so much of a level. I did try using live view and adjusting focus and that worked fine indoors. I can see in any sort of wind this would not work well.

Thanks

No problem Doug. I should have added that, having tried various configurations of DSLR+Lens for digiscoping, I still find using a compact camera is easier to use, & better in terms of connection/balance and also the camera's AF system seems more accurate and responsive in actual use. Not to mention that shutter speeds are higher, which is all important in digiscoping.

There is a theoretical advantage in using a camera with a larger sensor but in my personal experience the trade off is barely worth it (with the possible exception of video).

I see you also use long lenses for bird photography. I have seen some very good results with e.g. Canon's 400 f5.6 & stacked TCs that gives very similar mag to digiscoping with the system described above (ATS 80/20-60 zoom/compact with 3x zoom). The long lens option also offers more versatility in terms of flight shots/ other applications etc. For absolute reach my digiscoping set up with a compact has the edge (just) but it's a close call.

BodyResults · Oct 5, 2012

Well I got home tonight just as the sun was going down so I decided to give it a quick try. Luckily there was an Anna's Hummingbird hanging out on the neighbor's bush right next to some flowers it likes.

I used the 50mm f1.4 at f1.4. Becasue these was so little light I cranked the ISO all the way up to 6400 on my Canon 550D. Adjusting for proper exposure and having the scope wide open at 20X only gave me a shutterspeed of 1/50 sec.

Attached are my very first tries of digiscoping a bird. While these pictures aren't great I feel good about the quality given it was my first time, I used ISO 6400 and only had 1/50ss.

In good light and with practice I think these might come out decent.

One thing I noticed was shooting through the scope wide open at 20X the camera was losing about 6 stops of light compared to if I shot the same scene without the scope. Then when I tried to zoom in to 60X I seemed to lose another 2-3 stops of light.

That's it for now. I'll try more this weekend.

Paul Corfield · Oct 5, 2012

I posted a thread a couple of years ago showing this but just to show the theory does work. 4 images with a 50mm lens ranging from f1.7 to f16 all at the same shutter speed on a 25X eyepiece.

Photos were from left to right, f1.7, f5.6, f11 and f16, all at ISO1600 and all at 1/50sec

To photograph the same image with just my camera lens, at f16 I was at 1/60 sec and at f1.7 I was at 1/4000sec to get the same exposure.

Paul

BodyResults · Oct 7, 2012

Interesting Paul. I have no idea what is going on in your setup. I know in mine it behaves as one would expect. Every change in aperture affects the light getting to the sensor.

BodyResults · Oct 7, 2012

I went out in the field today for my first real tests of the Vortex Razor HD with my canon 550D. I mostly used my 50mm f1.4 in this setup.

I used manual focus and tried focusing through the eye piece and on live view at 5X. still not sure which one I prefer. Focusing through the viewfinder had the advantage when I need to move the scope to view something else. It just seemed smoother to lock on to another target.

I'll have to practice more on getting sharper focus. I felt today's images could have been better with a better focus.

Attached are 3 images. They are all of the same target area which I estimated to be about 120 meters away. The first 1 is through the scope at 30x the second one is full zoom at 60x and the 3rd one is a 100% crop with my Canon 7D and 400mm f5.6.

My primary goal of digiscoping will be to ID birds from pictures that are out of reach with my camera setup. Because I have 500mm f4 I feel that I can use that to ID birds up to about 200 meters. I would like to be able to use the digiscope for ID purposes in the 200 to 400 meter distance. Not sure how reasonable this is but I going to see how it works.

All comments and feedback welcome.

Paul Corfield · Oct 7, 2012

BodyResults said:
Interesting Paul. I have no idea what is going on in your setup. I know in mine it behaves as one would expect. Every change in aperture affects the light getting to the sensor.

The eyepiece projects an image at a certain diameter and this is known as the exit pupil. The exit pupil of an eyepiece is usually only a few mm in size because the human eyes pupils can only open to around 7mm (in the dark). The eyepiece on the Vortex has a variable exit pupil because it's a zoom and the specs list the exit pupil as being 4.25-1.42 mm. When you photograph through the eyepiece with a dslr lens you shouldn't see any change in the image until the iris blades start to cut into the image at the exit pupils diameter and at that point it would make it darker. On my set up that theory is working correctly as my series of images show. Just changing the aperture of the lens wouldn't work as expected because until the iris blades cut into the narrow image projected by the eyepiece, there would be nothing to darken.

Paul.

Paul Corfield · Oct 7, 2012

The images of the gulls show the heat haze that has been talked about in your other thread on long distance imaging. The out of focus bokeh in the background in the first and third photo shows shimmering air currents perfectly.

Paul.

BodyResults · Oct 8, 2012

Paul Corfield said:
The eyepiece projects an image at a certain diameter and this is known as the exit pupil. The exit pupil of an eyepiece is usually only a few mm in size because the human eyes pupils can only open to around 7mm (in the dark). The eyepiece on the Vortex has a variable exit pupil because it's a zoom and the specs list the exit pupil as being 4.25-1.42 mm. When you photograph through the eyepiece with a dslr lens you shouldn't see any change in the image until the iris blades start to cut into the image at the exit pupils diameter and at that point it would make it darker. On my set up that theory is working correctly as my series of images show. Just changing the aperture of the lens wouldn't work as expected because until the iris blades cut into the narrow image projected by the eyepiece, there would be nothing to darken.

Paul.

Paul, my apologies to you. You were correct about the aperture not changing the amount of light getting to the sensor.

It turns out when I make the aperture smaller (f1.4 to f2.8) in aperture priority mode the camera does lower the shutter speed by two stops. However when the pictures is exposed the one at f2.8 is now overexposed.

Also, interesting was in live view mode when I would make the aperture smaller (leaving shutter speed the same) the liveview image would get darker. However when looking at the picture taken in review it was exposed correctly.

Thank you for the education on this.

Doug

BodyResults · Oct 8, 2012

I did a bit more testing today at home. The light was a bit better. Below the first two shots are digiscoped with the 50 f1.4 at iso 1600, f1.4 and 1/1600sec. The third is from my Canon 7D with 500 f4 and 1.4 extender to give me 700mm at f5.6 iso 400 and 1/1250.

Seems like I just couldn't get the sharp focus on the digiscope setup.

Lens advice for Canon 550D on Vortex Razor HD (1 Viewer)

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