Dot Sight Device

[sillbeers15]

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A third party maker Dot Sight Device (used on riffles to assist precision sight & aim) with a coldshoe attachment can be mounted on the hotshoe of a camera to perform as a target/sight locating device instead of using the camera's EVF or LCD for the following purpose when a telephoto zoom exceeding 200mm in focal length is mounted onto DSLR/Mirrorless:

1.   Fast target location over EVF/LCD as user sees the complete view upfront beyond EVF/LCD especially tracking a subject to fill the entire frame;

 

2.  More accurate tracking subject as dot sight device's viewer is fixed size and clarity irregardless of lens focal length and shallow depth of view;

 

3.   Addresses the short coming of lens focus hunting problem that removes target sight in EVF/LCD that forces the tracking of fast moving subject to be terminated.

 

The first BIF pics shows an actual image taken using the Sigma 150-600mm (@600mm) this morning aimed with the dot sight device mounted on SL2 and camera settings: ISO800 / F6.3 / 1/3200sec / AFC / Tracking mode / Medium drive speed.

The second pic taken with iPhone (ignore the poor image resolution) showing the center frame of the Dot Sight device (with the red cross hair) calibrated to the center of frame of the SL2's EVF (with white cross hair aimed at the tip of the lighting protector on my neighbour's roof).

 

 

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[jaapv]

It also shows the problem of such a device, that it must be mounted quite high to avoid being obscured. by the front of the lens, which will lead to perspective shift. Thus it must be adjusted for each distance.

Another problem is the tracking mode. You must first "hit" the subject with the AF to make the camera lock on; I suspect that Multifield would be more consistent. 

I tried a similar construction using a 13,5 cm viewfinder. 

[sillbeers15]

17 minutes ago, jaapv said:

It also shows the problem of suc a device, that it must be mounted quite high to avoid being obscured. by the front of the lens, which will lead to perspective shift. Thus it must be adjusted for each distance.

Another problem is the tracking mode. You must first "hit" the subject with the AF to make the camera lock on; I suspect that Multifield would be more consistent. 

I tried a similar construction using a 13,5 cm viewfinder. 

What you have described is relevant.

Based on my user experience, the Multifield mode certainly makes focus lock much easier, however it was only useful when the background is plain. ie the sky or waters. When the BIF subject enters the bushes, the Multifield autofocus selection quickly becomes useless. Therefore I have sticked to tracking mode over AFC so far. Then again, the dot sight device worked like a charm on my SL90-280mm with high AFC success rates. Using the same device over the Sigma 150-600mm, I start getting lower AFC success rate with Autofocus Tracking mode. Both in terms of locking focus and sharp pics. I am still experimenting with different AF settings to determine the optimize methodology. I am also seriously looking at how best can I avoid perspective shift ( due to the inconsistent results I'm receiving so far). At 600mm focal length, the angle of view is less than 5% vs 46% for a 50mm lens. I would be happy to hear other user experience of the dot sight device over the Sigma 150-600mm.

 

[jaapv]

I consider a DIY construction with a mark on the screw of the hood and a the 135 mm viewer mounted high and tiltable.

[sillbeers15]

1 minute ago, jaapv said:

I consider a DIY construction with a mark on the screw of the hood and a simple frame on the hot shoe. 

Your intended purpose is to drop the dot scope mounting height?

On my SL90-280mm application, I screwed the dot sight device directly onto the base of the lens tripod mount as it could be detected easily and re-position above the lens for dot sight device mounting. Perhaps I should the same for Sigma 150-600mm?

[Boojay]

If you feel it's working and helping then that's all that matters, but it's not convincing me to try it out😉.  

Having used rifle sights I can understand your thinking behind it but apart from the frankensteinian  looks, I can't see how it helps with focus lock, while looking through the sight the camera could be focussing anywhere surely.  Certainly wouldn't want to carry that lot out in the field, and the beauty of the 150-600 to me is ability to shoot handheld.

The reason for differing results between 90-280 and Sigma 150-600 is just down to focal length, less dof, and more room for error.  

The only answer for me is more practise I'm sure, here to learn and always interested to see and hear others experiences and suggestions.

 

 

 

[sillbeers15]

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2 minutes ago, Boojay said:

If you feel it's working and helping then that's all that matters, but it's not convincing me to try it out😉.  

Having used rifle sights I can understand your thinking behind it but apart from the frankensteinian  looks, I can't see how it helps with focus lock, while looking through the sight the camera could be focussing anywhere surely.  Certainly wouldn't want to carry that lot out in the field, and the beauty of the 150-600 to me is ability to shoot handheld.

The reason for differing results between 90-280 and Sigma 150-600 is just down to focal length, less dof, and more room for error.  

The only answer for me is more practise I'm sure, here to learn and always interested to see and hear others experiences and suggestions.

 

 

 

I only shot both my SL90-280mm (for more than 4 yrs) & Sigma 150-600mm handheld. It is only to demonstrate that both camera lens & dot sight device coincide and calibration that a tripod is used. When you start chasing fast moving subjects, you will experience the limited ability to accurately focus lock or worst loosing the subject entirely in the EVF when the lens starts focus hunting. Even a simple task of keeping BIF with frame over continuous shooting can be challanging when your subject almost fills your frame.

[Boojay]

2 minutes ago, sillbeers15 said:

I only shot both my SL90-280mm (for more than 4 yrs) & Sigma 150-600mm handheld. It is only to demonstrate that both camera lens & dot sight device coincide and calibration that a tripod is used. When you start chasing fast moving subjects, you will experience the limited ability to accurately focus lock or worst loosing the subject entirely in the EVF when the lens starts focus hunting. Even a simple task of keeping BIF with frame over continuous shooting can be challanging when your subject almost fills your frame.

Oh.. I totally understand all of that... been trying long enough, mostly DSLR days with Canon though (15 yrs).    With the 150-600 so far I have been using the hood lock (push/pull) and zooming in and out to re-acquire focus, fun, frustrating, when it's no longer fun I'll stop!   

 

 

[jaapv]

13 minutes ago, Boojay said:

If you feel it's working and helping then that's all that matters, but it's not convincing me to try it out😉.  

Having used rifle sights I can understand your thinking behind it but apart from the frankensteinian  looks, I can't see how it helps with focus lock, while looking through the sight the camera could be focussing anywhere surely.  Certainly wouldn't want to carry that lot out in the field, and the beauty of the 150-600 to me is ability to shoot handheld.

The reason for differing results between 90-280 and Sigma 150-600 is just down to focal length, less dof, and more room for error.  

The only answer for me is more practise I'm sure, here to learn and always interested to see and hear others experiences and suggestions.

 

 

 

I would trust the camera to lock focus (hence no tracking) as everything is going too fast to check focus anyway. I agree that the lens intrusion is the main problem with these external sight constructions. Still, I would love to be able to see  outside my field of view.

[jaapv]

I just ordered the Olympus EE1

[Boojay]

33 minutes ago, jaapv said:

I just ordered the Olympus EE1

I will be really interested to hear how that goes Jaapv, it looks an interesting option, though some things still leave me wondering if it's really going to help.  Having just watched this you tube video, I'm guessing with the 150-600 you would set it up for 600mm, as it seems you have to calibrate for different focal lengths.  Please keep us posted.

 

[jaapv]

I'm off to Zanzibar in a lodge next to a bird reserve forest end of next week. I hope to get some nice bird shots then. Stay tuned.

[Boojay]

4 minutes ago, jaapv said:

I'm off to Zanzibar in a lodge next to a bird reserve forest end of next week. I hope to get some nice bird shots then. Stay tuned.

Brilliant... lucky you - enjoy!

 

[sillbeers15]

5 hours ago, jaapv said:

I just ordered the Olympus EE1

+1. Tried & tested the dot sight device, it works well and since the Olympus unit is better built.

[jaapv]

BTW. If you remove the hood, the hot shoe tower can be reduced considerably. I tried it with my 135 mm viewfinder.

[jaapv]

On 9/18/2021 at 12:01 PM, jaapv said:

I just ordered the Olympus EE1

Just got it on n. Actually it appears to be quite good. Sleek design well built and quite effective. On the CL I needed a hot shoe adapter to clear the lens hood of the 150-600, on the SL probably not needed. Centering the dot was a matter of a couple of minutes. I’ll try it out next week but I think it will work just fine. LCD to frame, dot sight to aim and multi field to focus I guess. It 

[Ktsa5239]

The Olympus looks promising, I imagine using zone focus with the dot might be easier than just the evf especially now the AF is more accurate after the update. 

[jaapv]

iI don’t think that zone focus will be very effective when DOF is a few cm.  Why not use the excellent AF of rhe 150-600?

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[sillbeers15]

27 minutes ago, jaapv said:

iI don’t think that zone focus will be very effective when DOF is a few cm.  Why not use the excellent AF of rhe 150-600?

you can select AFS or AFC combined with either Tracking / field / Zone depending on the type of background ( focus might select background over subject if zone focus is selected). The dot sight device can come in handy when the lens start hunting (shutter trigger release will not work and subject disappears from EVF/LCD screen) happens. All you have to do is to continue following the subject via dot sight until the focus is successful and the shutter trigger gets released.

[jaapv]

Indeed, and bird photography needs as critical focus as possible. Zone focus with a DOF of 30 cm @ 30 m is a no-go. It is a pity we have no trap AF. I use prefocus-trap for manual lenses, but that is another story.