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Old Friday 11th July 2008, 08:56   #1
bartolli
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Camera focussing problems

For several months now I have been playing with the various settings on my canon a510 and generally failing quite miserably when it comes to focussing thro my bresser scope.

I use a swingout adapter, scope at min zoom (20x) and just enough camera zoom to get rid of vignetting. I locate the target, focus the scope and swing the camera back to take pics with a cable release.

I generally shoot at ISO 400, but use 200 if light permits. Usually I have the camera in aperture priority mode and use centre spot exposure (although I have also played witrh centre-weighted).

For focussing I originally used the option where the camera picks one of nine central squares, but then changed to spot focus in the central square, yesterday I tried the 9 square option again. (There is probably a technical term for this!)

I have tried the above with the camera in macro and landscape modes, I have tried manual focus with the setting at infinity.

I have also tried manual focus, but find it virtually impossible to tell from the LCD screen whether the focus is ok.

I have tried pushing the release half-way and then refocussing the scope but again this relies on the LCD screen to see if the pic is in focus.

Occassionally, using any of the above settings, I get one or two shots which are in reasonable focus. None of the above settings seem to have any better success rate than the others.

The only way I have found to improve the situation is to have no zoom at all on the camera. The photos are then quite well focussed but I obviously end up with BIG vignetting. I can crop/resize these but with 3.2mp this is a bit limited.

So, what am I doing wrong with the focussing? Any suggestions whatsoever greatly appreciated as I am getting a bit frustrated, especially when I see all the beautiful photos on this site!! Note that I don't really expect to take awesome photos, I just want some that are reasonably well focussed!

Thanks for reading this far!

The attached pic has just been cropped to get the size within limits.
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Old Friday 11th July 2008, 09:45   #2
IanF
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I think that anyone would struggle in these circumstances. For digiscoping you really need a scope with high quality glass such as ED, APO, fluortite etc. which reduces chromatic aberration and improves sharpness. I think the Bresser has ordinary glass. Even scopes from the big brands have two ranges - ED and non-ED scopes - with the latter nothing like as good for digiscoping.

Overall the photo shows detail in the foliage and even the rocks but very soft and grainy with quite a lot of CA (bluey-purple) in shadow areas - which I suspect is down to the optic quality rather than technique - though there does seem to be some movement as well.

Having said that you should still be able to get reasonable results under some conditions. Ideally you want the sun behind you shining onto the subject preferably early morning or late afternoon with a bit of a breeze so heat haze is reduced and with the subject quite close - c.20m. That way CA will be minimised.

Using the whole image downsized will give apparent sharpening and whilst the subject will be smaller in the frame overall will be quality much improved. Try just cropping to remove vignetting and then resizing to smaller than you usually use - things should look better.

Other than that your technique sounds pretty good. How stable is your tripod though? Even a top end scope will produce soft pictures if the tripod isn't stable enough. Even a heavy one needs to be firmly positioned and everything tightened down. Apart from wind affecting things, walking near the legs and touching the camera imparts vibrations that take several seconds to settle down.

Maybe worth setting things up in your garden or park and taking photos of something quite close 8-10m using the camera timer at 10 sec and shutter release cable to see if things improve.
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Old Friday 11th July 2008, 16:22   #3
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While achromatic (non-APO,ED) glass can lead to a loss of contrast and SOME color fringing it shouldn't be as bad as you post.

I think the tip-off is when you said "The only way I have found to improve the situation is to have no zoom at all on the camera. The photos are then quite well focussed but I obviously end up with BIG vignetting. I can crop/resize these but with 3.2mp this is a bit limited."

Just a guess on my part but I think the optical match between your camera optics and the the scope's optics are way off somehow. There is something wrong besides the quality of your scope IMO.

A few examples of a properly matched NON-ED NON-APO scope to a DSLR camera...
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Old Sunday 13th July 2008, 08:48   #4
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Thanks for the comments.

IanF: My tripod is a velbon, I will try 10sec release next time I venture forth and see if this has any effect.

Maxxx: Could you try to explain what you mean by optical match?

I've spent the last 2 afternoons running off loads (approx 1000 in all) of shots in the garden, range about 10m.

Approx 80% of the shots I took with no zoom on the camera were ok for focus, whether I used 9 pt or centre focus. When I zoomed the camera, this rate dropped to about 20%. This would be acceptable if I could replicate this in the field where range is usually a lot more than 10m. But I guess if I'm getting 20% at only 10m range then I have no chance at higher ranges!

I also tried zooming the scope a bit (but not the camera) and again was getting ok results for focus. This seems to go against general advice to leave the scope unzoomed, I guess maybe I was fortunate that it was light enough.

I think I will have to live with not zooming the camera if I'm to get any half-decent shots, and if conditions allow I can zoom my scope a little bit.

The attached greenfinch was taken yesterday with the camera unzoomed and handheld to the scope.

The first photo was actually one of my first efforts (before I realised you could remove vignetting by zooming the camera!), since then my photos have generally been "a bit poor"! This photo shows 2 canada geese protecting their chicks from a couple of angry lapwings, meanwhile our recent celebrity black winged stilt watches on.

Thanks for your time, I will keep you informed of progress (or otherwise!)
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Old Sunday 13th July 2008, 09:56   #5
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"Maxxx: Could you try to explain what you mean by optical match? -"

OK in general:

You are using a complex setup with the light path going through two zoom lens' both of which may be set independently of each other. On axis alignment between the two lens' is critical. Also your zoom lens on the camera moves back and forth in relationship to the eyepiece zoom and this could be throwing off your focus. Also as you zoom up in power the image gets dimmer so the auto focus may not work well in the camera. Finally the camera lens and zoom eyepiece just may not be a good match no matter what you do.

I am not the best person to ask about this. I don't shot through a PS camera and a zoom lens so most of the issues I'm talkin about here are a non-issue with me.

Perhaps there are others that could give you advice in more detail than I can.

good luck,
Maxxxx
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Old Sunday 13th July 2008, 19:49   #6
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Bartolli,

I believe that your problem is that your camera will not focus closely enough to come to focus through your scope when you have zoomed in. I have the same issue with my Canon A570.

Here is why I believe that is your problem. When you shoot at maximum wide angle (no zoom) your images look pretty good. At this setting your camera will focus down as close as 2" (5 cm). As soon as you zoom at all your camera will only focus as close as 11.8" (30 cm). Some experimentation will my A570 showed that my camera needed to focus at around 9-10" to match what I saw as in focus visually. This would mean that you could not zoom and still come to focus.

There is a way around your problem. Here is what has worked the best for me:
-Depress the shutter release half way
-Hold the shutter release there
-Re-focus your scope using the camera's display
-Remove your finger from the shutter release
-Depress the shutter release half way again and recheck focus
-Repeat if necessary

Depressing the shutter release half way will lock the auto-focus.

Adjusting the scopes focus after the camera has gotten as close to focus as it can should allow the camera to come to a sharp focus.

I find that I get the best results if I adjust focus a little beyond what looks sharp, that gives the camera some latitude to come to sharp focus.

Also, since you are using the camera auto-focus again after you make your scope focus adjustment the focus is less critical compared to manual focus.

I know that it is counterintuitive that you should change your scopes focus from what looks sharp to you visually, try it and let me know how it works for you.

Good luck,
Mike
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Old Tuesday 15th July 2008, 14:53   #7
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OK Chaps, many thanks for all your suggestions, greatly appreciated.

jmepler: I tried your suggestion and vast improvements, see photos attached. The only mods I have done is cropping, slight rotation & resizing. OK they aren't brill but vast improvement and with a bit more practice should get better.

The blue tit was taken in our garden at 10m, the others at a similar distance (75-100m) to my very first posting. The lapwing is actually in the same place as the very first post, so the improvement here is obvious!

Many thanks to everyone for your time!
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Old Tuesday 15th July 2008, 16:30   #8
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Bartolli,

Another consideration that can affect overall image quality is noise, which seems exceptional in most of the images here. As an avid point & shoot user, I default to 100 or 200 ISO only to avoid pixellation from higher ISO's (I find 400 too noisy). I understand this means slower shutter speeds and some images will be missed due to motion blur, but I've gotten some great images even at full 1 second exposures at times. The Streak-chested Antpitta image attached below is one of these that was shot on a cloudy day under the full Canopy of rain forest near the Canopy Tower in Panama!

Just for fun, experiment with the lower ISO's and higher ISO's on the same subject and see what you find. At these lower shutter speeds I recomend use of 2 sec delay or cable release, and shooting in shutter bursts. That way if/when the bird moves you are more apt to get a crisp image. Limiting these variables will give you the best images possible, however this will always be limited by the lowest quality link in your set up be it glass in the scope, camera lens, compatibility between the two, tripod, adapter, etc. It takes a while and some testing to realize the limitations of any setup and best bets for eliminating these as best you can, but once done you can generally get consistent best results for any given system.

Also, in low light don't forget your movie mode. Sometimes for documentation a series of frames in a clip can provide a better image as well, even though this are more comressed.

Best,

Jeff Bouton
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Old Wednesday 16th July 2008, 08:11   #9
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thx Jeff.

The blue tit was taken at ISO400, the others at ISO200. I generally set the ISO to give a decent shutter speed to suit the conditions, but you're right I need to experiment a bit more!

I generally use a release cable & shoot bursts of abt 6 shots at a time.
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Old Wednesday 16th July 2008, 08:19   #10
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In the first image of your second posting, it shows vignetting in just one corner, is this left behind after cropping, or is as taken, if so your camera and scope are not aligned properly, this could have an adverse effect.
You do not say how the two are interconnected, can you slide the camera back and forth so you can adjust for the zooming of the camera, have you tried adjusting the distance between scope and eyepiece, some setups need a space between them, some do not. Ernie
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Old Wednesday 16th July 2008, 08:30   #11
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I have just looked at the preview of your camera and it looks just about the same as the A640 that I use, I have used this with an acromatic type scope with excellent results, so there is no reason that you should be getting the results you are. Zoom eyepieces are not the best for digiscoping, but do work. I would suggest that the method of connection is at fault here, How are you connecting them, if you are using the adapter made by Canon for attaching conversion lenses, you will be flat out getting good results. Ernie
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Old Wednesday 16th July 2008, 09:15   #12
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Can you change the eyepiece on the Bresser? I've had quite a few low end spotting scopes that were useless for photography with the eyepiece that came with them. Once I changed the eyepiece for a decent one the problems were solved. I've also bought cheap spotting scopes on ebay and just used the objective lenses to make my own refractors. They all gave excellent performance for viewing and photography when used with a high end eyepiece which shows the eyepieces on these cheap scopes are quite poor.

From experience I'd say that your photos are the result of the zoom eyepiece. If the Bresser scope is too good to modify then upgrading to something better is your best bet.

Paul.

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Old Thursday 17th July 2008, 09:02   #13
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Again thanks for all your comments and time!

Ernie: The canada geese shot was one of my "first" efforts when I was handholding the camera against the eyepiece without any aids at all. The remaining vignetting is just the result of the crop. The shot of the greenfinches was again handheld against the eyepiece but using a cut-out film cannister lid to centre the camera within the eyepiece cup.

Stirred by my "success", I thought an adapter was a worthwhile investment & bought a visionary "L" swing-out adapter, all the other photos I have posted were taken with this adapter. In hindsight I may have been better getting the SRB-G adapter.

Your comment does raise the issue that I have noticed that when using this adapter, the ring is not centred on the LCD screen (but it is when I handhold). This is a bit strange because when using the adapter the ring is sharp and complete, but if I try to move the camera to get the ring centred then the ring goes hazy & not complete!

Generally when setting up the adapter, I set it up with no zoom and the lens against the eyepiece and adjust the position to get the ring sharp/complete. I then slight zoom the camera to get rid of vignetting, note that the slight zoom actually retracts the camera lens a bit, so the lens is a few millimetres away from the eyepiece when taking the shots.

I have tried my handholding method (with the cannister lid) so that when zooming the camera, the lens is still against the eyepiece, more or less same results.

The canon adapter you mention, is that the ringthing which replaces the screw ring around the lens? If so how do I use this to attach the camera to the scope?

Paul: As far as I am aware I cannot change the eyepiece. I'll start another thread to see if anyone else has experienced such probs with a bresser.

So far, there seem to be 3 possibilities, or poss a combination of these?:

1) Camera can't focus down thro scope when zoomed, solution use jmepler technique;
2) Quality of scope/eyepiece or using zoom eyepiece;
3) Adapter not adequate;
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Old Friday 18th July 2008, 10:26   #14
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Getting a bit better!

OK, dashed off to Burton Marsh yesterday to see the Glossy Ibis & took the opportunity to put into practice some of the suggestions thus far.

Before going I tinkered with the adapter a bit to try to centre the vignette in the viewfinder a bit more, possibly the angular alignment was a bit off?

Anyway, fairly good results overall using jmepler suggestion again, but still room for improvement I think. Light was far from ideal, being fairly overcast, so I am greatly encouraged by the results, thx to everyone for assisting thus far.

The attached photos have not been modified apart from resizing and cropping.

The heron was only about 25m away, the common terns were about 100m, the fox appeared on the other side of the lake about 100m, the Ibis was approx 50-75m away and the ruffs(?) maybe 15-20.
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Old Friday 18th July 2008, 10:35   #15
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All pretty good results

You're right in that the camera lens/adapter should be parallel to the scope eyepiece and not at an angle.
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Old Friday 18th July 2008, 20:34   #16
Texun
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Bartolli, Excellent results are a combination of excellent equipment and excellent technigue. My equipment of choice is:
Canon A640 camera

Home made adapter capable of setting exact optical centering of scope
and camera axes.

Pentax 14mm XL eyepiece.(provides 25X with scope below)

Takahashi FS-60C Astronomical scope.

Home made shutter release cable bracket.

My technique includes using the lowest possible ISO, use of auto focus, use of spot focus, use of spot metering in difficult lighting situations, no or minimal camera zoom, and always using a cable release. Add lots of practice.

I'm attaching a photo of my setup and a recent image (Texas Spiney Lizard) so you can see what happens when everything comes together.
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Old Tuesday 22nd July 2008, 09:37   #17
bartolli
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thanks all.
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