A question of optics

A question of optics

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  • #24663
    Sam Stones
    Participant
      @samstones42903

      Use of close-up lenses on video camcorders

      #248434
      Sam Stones
      Participant
        @samstones42903

        Gentlemen

        I know there are some of you with specialist knowledge in cameras and lenses.

        I'd like to get in close and personal with some inanimate objects e.g. my skeleton clock. I have a Camcorder which has a (58mm) threaded lens for attaching filters etc.

        The camera is fitted with a Canon HD Video (3.67 – 73.4mm) 20x zoom lens.

        If I attach a quality (i.e. two-element) close-up lens (say 2 or 4 diopter), will there be much (or any) falloff in image quality?

        Thanks for any help,

        Sam

        #248436
        Bob Stevenson
        Participant
          @bobstevenson13909

          If you are using an ordinary domesic camcorder with fixed lens then close up lenses are pretty much your only option. However, decently made close-up 'supplementary' lenses work quite well for still photography so should be quite alright on a camcorder even when using HD. You don't have much to lose and even a simple, one element uncoated lens can give quite good reslts so try it and see….if you can find someone wih a close-up lens then attach it temporarily with tape or blu-tak and try some video to see for yourself what it looks like…..I doubt you will be disapointed………   Once you have 'proof of concept' you can buy a cloe-up lens with 58mm thread to fit your camcorder.

           

          …………There may well be someone here who will send you a close-up lens that they no longer use as a kindly gesture. Not many stills photographers use them now because many modern cameras either have interchangeable lenses allowing 'macro' lenses, extention rings or bellows to be fitted….or have fixed zoom lenses with a special close-up facility.

           

          Also, remember that most digital pocket cameras, although small, usually have video facilities of varying cleverness, and also commonly have a close up feature too……….if you can borrow a friends camera for a try you may well find that this offers a better video for close-up than your camcorder.

          Edited By Bob Stevenson on 29/07/2016 06:31:50

          #248440
          Michael Gilligan
          Participant
            @michaelgilligan61133

            Sam,

            Obviously other brands are available; but, the Minolta ones from the 1970s are the best achromats I have tried.

            These were quite useable on full frame 35mm, and are excellent on micro four thirds … So I would also expect good results on a camcorder.

            It's well worth searching for these secondhand.

            MichaelG.

            #248444
            Neil Wyatt
            Moderator
              @neilwyatt

              I see the world through a pair of 3.5 dioptre single-element lenses.

              Whilst there is CA in the corners, it's not particularly noticeable.

              I doubt that you would see any significant loss in quality with a cam corder.

              Neil

              #248454
              Michael Gilligan
              Participant
                @michaelgilligan61133

                Posted by Neil Wyatt on 29/07/2016 07:56:02:

                I see the world through a pair of 3.5 dioptre single-element lenses.

                Whilst there is CA in the corners, it's not particularly noticeable.

                .

                A good point, Neil, and well made

                But you omit any reference to curvature of field, which is typically a significant problem with photographic close-up lenses. … Your retina is [approximately] part-spherical, but the camcorder sensor is flat.

                The importance of field flatness will, of course, vary according to the cosen subject.

                MichaelG.

                #248508
                Ajohnw
                Participant
                  @ajohnw51620

                  I've had good results on a dslr using an achromatic one. I'd just advice not to go too strong. Quality varies. The one I have had best results with was made by sigma for one of their zoom lenses some years ago. I tried a supposedly Canon one and it was hopeless and later found that Canon didn't actually make them. I've also tried some other screw on stuff intended for compact cameras – nvg.

                  I would suggest you try one of these. They clip on and the brand has a good name. You may need to fit a step up ring to get it to fit but it does cover a range of sizes as it comes.

                  **LINK**

                  They also make a stronger one, the 250.

                  The sigma ones crop up on ebay now and again and aren't overly strong. I use mine on a 75-300mm zoom lens on micro 4/3. Quality doesn't drop off until around 220mm or so. I posted a link to some shots I took with this some time ago. I get decent levels of magnification of things like bees from a distance of about a foot or so.

                  You should bear in mind that depth of field drops off as magnification is increased. By increased I mean closer focusing than a typical camera lens. Some cameras will focus down to a couple of cms at the wide angle setting but that sort of working distance is pretty useless.

                  John

                  =

                  Edited By Ajohnw on 29/07/2016 12:24:47

                  #248513
                  peak4
                  Participant
                    @peak4

                    Again, I'd suggest looking for an Achromatic lens, likely with 2 elements. I've had decent results on m4/3s with the Sigma variety. Note that not all Sigma close up lenses are achromats.

                    This one is listed as UK delivery, but you could ask if he'd post to your part of the world.

                     

                    On the other hand, if the lens is a plain C mount, would it be possible to add an extension tube between it and the camera body?

                    Edited By peak4 on 29/07/2016 12:49:17

                    #248515
                    Ajohnw
                    Participant
                      @ajohnw51620

                      This page might help you decide what strength of lens you need.

                      **LINK**

                      You'll probably have to work out the native magnification of the lens on the camera. It relates to to size on the image on the sensor and the size of the object. To give you some idea it doesn't always need a lot of dioptres to reach one to one and I'd guess that the sensor in your camera is pretty small.

                      If you go too strong you will find that you haven't sufficient width of field to cover what you want to photograph.

                      John

                      #248525
                      pgk pgk
                      Participant
                        @pgkpgk17461

                        ..or if you want to get really close for under £20 : **LINK**

                        ..not that I've tried this..

                        #248575
                        Neil Wyatt
                        Moderator
                          @neilwyatt

                          Posted by Sam Stones on 29/07/2016 04:14:18:

                          inanimate objects e.g. my skeleton clock.

                          If your clock is inanimate, why do you want to take moving pictures

                          I hope your next clock shows more signs of movement

                          Sorry….

                          Neil

                          #248581
                          Ajohnw
                          Participant
                            @ajohnw51620

                            devil The amazon close up lens I linked to was initially aimed at higher end video cameras. Weird what ?

                            **LINK**

                            The site might even list your camera.

                            John

                            #248583
                            Michael Gilligan
                            Participant
                              @michaelgilligan61133

                              Sam,

                              I just found this page, with some good sample shots using the old Minolta achromatic close-up lenses.

                              https://joerghaag.com/2015/06/24/achromatic-lenses-the-always-with-you-macro/

                              Click on the images to see them in full resolution.

                              MichaelG.

                              #248585
                              Sam Stones
                              Participant
                                @samstones42903

                                Hey Neil,

                                I imagine that getting in close and personal with animate objects is a bit too risky at my agedevil

                                I did capture the clock's escapement in slow motion (on a Sony Handycam). Slowed significantly via PowerDirector proved to be a big help to another clock enthusiast. Sadly, there won't be another clock out of my stables.

                                As for the CU lens/filter issue, I'm still trying to resolve the issue. Your comment about ` … seeing the world through a pair of 3.5 diopter lenses …' sent me scurrying for my best `readers'. However, the (rather crude) camcorder tests simply showed how bad my astigmatism really is.

                                I must thank every Forum member who contributed.

                                Good gear chaps!!!

                                I'll be back on this one shortly (or longly).

                                Regards,

                                Sam

                                #248586
                                Neil Wyatt
                                Moderator
                                  @neilwyatt

                                  (I'm up late, letting my camera take multiple images of (hopefully) the North America and Pelican nebulas.)

                                  HD isn't very demanding on optics, its only1080 pixels wide. Is it worth experimenting with a cheap +2 dioptre lens like THIS?

                                  The other trick that works VERY well is a lens reversing ring, I still have a 52 – M42 one from years ago.

                                  Neil

                                  #248588
                                  Sam Stones
                                  Participant
                                    @samstones42903

                                    Hi Neil,

                                    It's heading for lunch time down here, and at last some sun is breaking through the clouds.

                                    Both of your ideas make sense, although I hadn't thought of reversing a lens. It should be easy to test by holding another lens (back to front) in front of the camera.

                                    Internet pictures of the North America and Pelican nebula show some spectacular colours. Good luck.

                                    Gentlemen all,

                                    I don’t know who to thank the most, so thanks to everyone.

                                    There is certainly much (more) food for thought, and I now find myself in the awkward position (geographically) of `Try before you buy’. We are short of good camera shops close to where I live, and as yet, I’m not ready to splash out buying on line.

                                    Here, however, is a bit of the background.

                                    One of my many reasons for replacing a small Sony Handycam with this particular camcorder (a Canon Legria HF G40) was that my still camera is also a Canon (EOS 300D/Digital Rebel) and, like the camcorder, it too has a 58mm threaded lens.

                                    With the still camera, I can get up close with either a Novoflex bellows and a choice of three lenses. Or I can simply jump in with a Canon 100mm macro, all of which have electronic coupling. With a couple of 58mm filters already in my camera kit (e.g. a circular polarising filter), it seemed like a good idea to aim for a little bit of compatibility. Unfortunately, that’s where the interaction and compatibility ends.

                                    Unlike the still camera, the camcorder lens is not removable from the camera body hence why I’m looking at a screw in (58mm) supplementary (CU filter) lens. Just to complicate (or improve) matters, and besides a zoom range of x20, the camcorder has manual and auto focusing.

                                    That aside, there is something rather odd about moving in close with the camcorder which I can’t get my head around. At full telephoto, the image will not come into sharp focus if the camera is any closer than 60cm to the subject. Conversely, at full wide angle the minimum focus distance is 10mm (1cm).

                                    Regards,

                                    Sam

                                    #248590
                                    Sam Stones
                                    Participant
                                      @samstones42903

                                      Here are my attempts using a standard lens back to back with the camcorder lens, as highlighted by Neil earlier.

                                      The vignetting might come in useful when I'm feeling a bit arty.

                                      img_0073.jpg

                                      img_0076.jpg

                                      Holding the lens against the camcorder by hand, leaves a lot to be desired from a camera-shake point of view.

                                      Can't say the focus is all that brilliant either.

                                      All this is looking good, so I might bite the bullet and get me a two-element diopter CU-lens/filter/achromatic/supplementary/…

                                      No promises!

                                      Regards,

                                      Sam

                                      #248622
                                      Ajohnw
                                      Participant
                                        @ajohnw51620

                                        Vignetting can crop up with various arrangement usually worse with shorter focal length settings.

                                        The weaker Raynox lens may be too strong for you Sam. The 150 is 4.8 dioptres. It will fit lenses with a filter thread of 52 to 67mm. The fact that it clips on is pretty handy. They are actually a 3 element design. Some people use them for micro photography and get results like this. There are plenty of examples on the web.

                                        That will be a stacked image needed because of the extremely shallow depth of field at this level of magnification which will be well over 1:1.

                                        What I did to avoid wasting money was to buy a cheap set of plain glass close up lenses and try those first. What I found was that some lens – camera combinations I had wouldn't focus correctly even going as far as not focusing at all. I suspect this is due to the software in the camera expecting a certain rate of focal distance change and not liking it being speeded up as much as macro work does.

                                        John

                                        #249228
                                        Howard Lewis
                                        Participant
                                          @howardlewis46836

                                          A 50mm lens, from a 35mm camera, fitted in reverse, via a reversing ring, as Neil suggests is a highly corrected 20 Dioptre close up lens, far better than a simple meniscus supplementary lens.. All that you need is a ring with threads to suit the digital/video camera lens on one side and the still camera lens on the other. A 50mm f/2 lens with faulty diaphragm operation is a good (and cheap) means of doing this.

                                          Howard

                                          #249355
                                          Sam Stones
                                          Participant
                                            @samstones42903

                                            Thanks for that Howard.

                                            My brief lash-up this morning (without a reversing ring), shows the effects of using two different zoom lenses. They were a 100-300mm and the standard (18-55mm) lens fitted to my stills camera. These were reversed and `snugged up to' the Legria. This camera was zoomed to full telephoto (equivalent to 73.4mm [35mm]).

                                            With such minimal DoF it is extremely unlikely that I'll ever find a (video) use for all but the 300mm . I'm still in favour of a popping on a supplementary CU lens/filter.

                                            An interesting journey so far, so thanks for your help and interest.

                                            Sam

                                            PS – I forgot to insert the composite picture and risk losing this note. I'll be back!!!

                                            composite---300mm---18mm---iii---04-08-16.jpg

                                            Oh! I almost forgot – the graduations are millimetres. 

                                            Edited By Sam Stones on 04/08/2016 00:47:06

                                            #249363
                                            Michael Gilligan
                                            Participant
                                              @michaelgilligan61133

                                              Sam,

                                              Those are astonishingly good results … Well Done, Sir !!

                                              Canon has produced an amazing, 20x zoom, lens; and yet you have clearly demonstrated that it's capable of adaptation.

                                              I cannot find an optical diagram of the lens, but I do know that it has twelve elements … Such beasts are usually optimised by the manufacture, to work within a specific 'envelope'; but performance drops dramatically outside that range. …

                                              MichaelG.

                                              #249382
                                              Ajohnw
                                              Participant
                                                @ajohnw51620

                                                This wiki page quotes the rather simple sum for the magnification this set up gives

                                                **LINK**

                                                There are a couple of complications in using sums like this. It might be called real magnification onto the sensor. In other words the size the object will be on the sensor. The sensor may not be big enough. The other one is that cameras sometimes have 35mm equivalent focal lengths on them, not their real focal length.

                                                To save you looking the magnification is focal length of lens on camera / focal length of the attached lens. These need to be the actual focal lengths.

                                                The general idea of reversing a lens is that the back end is optimised for working at short distances. The front for working at a distance. So in this case both lenses ideally need to be focused at infinity. If not the magnification will be different and the corrections built into the lens less appropriate. In the other case when a lens is reversed and mounted on extension tubes the lens focus is used to focus the image on the sensor. Both are really set ups for achieving rather high magnifications. When a lens is mounted directly on extension tubes there comes a point as the magnification is increased where better results will be obtained with it reversed. Both set ups are for very short working distances really and magnifications over 1:1. I'd guess that Sam's camera uses a rather small sensor so 1:1 or anything like it is probably completely unsuitable.

                                                John

                                                #249477
                                                Sam Stones
                                                Participant
                                                  @samstones42903

                                                  Gentlemen,

                                                  What an interesting journey and who do I thank the most?

                                                  Anyway, thanks again to everyone for all your contributions, it's much appreciated.

                                                  Having already chosen to use both zoom lenses set at their extremes (see previous images), this morning I’ll be doing another couple of tests with the 100mm macro, placed to `rub noses’ with the Legria lens. Well not quite.

                                                  John suggests … in this case both lenses ideally need to be focused at infinity … which makes me think that setting both to shortest focal distance will be unnecessary. Probably worth a try while I’m at it.

                                                  In case I forgot to mention, the Canon Legria HF-G40 lens is fairly complex, but not intended to be removed. As for the sensor size, all I could find was 1/2.83-type CMOS 3.09Mp, which might mean something to those who understand.

                                                  Regards,

                                                  Sam

                                                  #249480
                                                  Michael Gilligan
                                                  Participant
                                                    @michaelgilligan61133

                                                    This may not be immediately obvious, so I think it worth mentioning:

                                                    As Howard suggested; 50mm [and perhaps a little shorter] lenses from 35mm SLRs are particularly useful, reversed, as high power supplementaries … The surprise benefit is that 'working distance' is slightly greater than one might expect.

                                                    The explanation is that such lenses generally need to be 'retro-focus' in that the back focal length is longer than the nominal focal length … This is necessary because they need to clear the SLR mirror.

                                                    Incidentally; when used reversed, the helical mechanism has no focussing effect [think about it]

                                                    MichaelG.

                                                    #249481
                                                    Sam Stones
                                                    Participant
                                                      @samstones42903

                                                      Thanks Michael,

                                                      I tried just briefly holding the lens as Howard mentioned, and it sure does bring things up close. But as you intimated, creating more working distance than one would expect.

                                                      I can hardly wait to get my hands on a 58mm Male-Male adaptor ring, if only to remove the slight hand tremor while I'm holding the lens in position and trying to keep the subject in focus.

                                                      I've learned even more from your `helical mechanism' statement.

                                                      When the lens is reversed it (the glass bits) remains stationary while the bayonet end moves in free air.

                                                      Another arrow in my quiver (perhaps that should be vibrato).

                                                      Regards,

                                                      Sam

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