SJ8 Pro minimal focus distance

Discussion in 'SJ8 Series' started by Sauron, Dec 8, 2018.

  1. karjak

    karjak New Member

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    All makes sense as to what you are saying. I actually missed reading the part in your posting of your estimate for clear focus at 30 cm. I did see the 8 cm figure and wondered if perhaps lens was not distanced correctly (threaded in too far?). It would be nice to know an actual official figure from SJCAM. Perhaps not a critical setting as most users not concerned whether it's 3 inches or 3 feet. In fairness I may not have the settings correct on the SJ8 for inside shooting. Side by side with the "real" 4K Thieye , the SJ8 didn't seem to match even on the more distant objects. Comparison Screen grabs in previous post.

    I think what Sauron and I both were disappointed about, was that we expected to obtain similar results in comparison to the cameras we previously used for nature closeups. I have used a LightDow 4000, LightDow 4K ultra HD, Apeman 4K, and Thieye T5edge "true"4K. All of these cameras are ultra wideangle and are in focus under 15 cm. I had a quick chance to set SJ8 on tripod next to stump with some peanuts. After letting it record about 30 minutes I only had wasted footage of blurry birds. I have a screen grab from the video. I am thinking lens was about a foot away. As I look at the more distant objects you are probably correct in saying the lens is ok.
     

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  2. Sulev Svilponis

    Sulev Svilponis Elite

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    I think, that SJCAM focuses those lenses to infinity, because they think, that it's the best compromise for action camera users. If they fixed the lens into the position, that is unscrewed by ca 15 degrees, compared to the current position, then the camera should take nice closeups. I have broken loose from the hot glue several lenses of my SJCAM cameras, and this trick works for all of them. But at closeup position you loose somewhat (or even much, depending on how deep into macro shooting you will go) of the far distant sharpness.

    I have posted this sample (camera SJ5000X, lens unscrewed by ca 15 degrees, distance to the subject ca 20 cm) before:
    https://www.flickr.com/photos/svilponis/26683491655/in/dateposted/
     
    Last edited: Feb 17, 2019
  3. karjak

    karjak New Member

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    I have to agree with you on that. Some snowboarder with cam on his helmet not concerned how his camera would record birds a foot away. I just wonder how wide the tolerance range is. If you would screw lens out say only 5 degrees would you loose infinity clear focus? SJCAM lists focal length of 2.8mm. Knowing FOV is 170 degrees I wonder if any way to calculate what minimum distance for objects to be in focus should be? I thought your picture of Hawfinch was great! That was a photo not a screen grab correct? I can see the loss of clarity in the background. Curious as how you took the picture?

    The Apeman A80 4K(interpolated) I owned similar to your SJ5000X. I was amazed at how close I could set camera to subject and get a clear screen grab from video. My attached picture of Rose Breasted Grossbeak is cropped a small amount but I thought pretty good for a still frame. I just leave my camera recording and walk away. I did return as not real 4K. I did notice also that background not clearly in focus so I am assuming lens maybe not turned in close enough. Maybe Sauron feels a little better about the camera after reading your comments. I don't think I am going to change lens setting unless I find out from SJCAM not set right and I wouldn't screw up by breaking the glue seal.
     

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  4. Sulev Svilponis

    Sulev Svilponis Elite

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    Unscrewing the lens by 5 degrees will only very slightly decrease the clarity of distant objects. But by 15 degrees will decrease it already considerably. You need to unscrew the lens by more than 720 degrees to fully unscrew the lens, so up to 180 degrees is pretty safe to unscrew it, for macro focusing. And that is, according to my taste, maximum usable range too, because the more you unscrew the lens, the longer the lens appears (the narrower the FOV will be) and the shallower the DOF.

    I don't know, how to calculate minimum distance for objects to be in focus. By testing with a camera, connected with a TV, I found, that I can go as close as few millimeters, and then the camera works like a microscope, but the DOF is so shallow, that I can take sharp photos of flat objects only.

    The Hawfinch was indeed a photo. I fixed the camera on the branch of the maple and shoot it remotely as I knew, that a pair of Hawfinches visited that tree often (because it was nearby my bird feeder). I have also tried to do interval shooting (time lapse photo mode), but that results with enormous amount of pictures to sift from, and as I take photos in RAW format, this wastes my disk space too. But I have captured some very nice pictures this way.

    You can see macro video quality from my video of tiny young natterjack toads:


    or of butterflies (sorry, I was testing with this video, and in some scenes I put hand held camera too close to subject, rendering it out of focus):
     
    Last edited: Feb 18, 2019
  5. karjak

    karjak New Member

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    Very nice videos and cool how you have experimented with this type of camera. I wish these cameras were sent out with the lenses movable. They could put a White centerline at middle above lens to line up with a small dot marking on the rim around lens. This so you go back to a preset position. Opens camera up to some more uses. I am myself a little apprehensive to try this out on this particular model. I did replace a lens on my HD LightDow LD-4000 with a glass lens but didn't think helped so went back to original. I do wonder on all these action cameras how careful they are threading in lens to make sure to have clear focus at infinity?

    As you mentioned with your Butterfly vid, it is handheld and butterflies and bees fall in and out of focus. Since you had such neat macro subjects I was curious what a screen grab would look like. I used VLC and was quite amazed how good your SJ5000X produced in Macro. Even from a downloaded mp4 at 1280x720 the screen captures look pretty good, even cropped ones. I would think a real 4K with lens turned out could give some great macro shots. Let me know if you want me to remove these pics but I thought you might be curious to what you could get from screenshots.
     

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