Dave Richards AA7EE

June 18, 2012

Photography and Air Spaced Variable Capacitors

Several people have commented to me that they enjoy the pictures I take for this blog, and Mike VK1oo recently asked if I could write a post detailing how I take them. I don’t want to turn this into a photography tutorial and acknowledge that there are other (and perhaps better) ways to take pictures for a blog, but this is how I take mine.

Firstly, I use a DSLR. There is a noticeable difference in the image quality that comes from compact digital cameras with their smaller image sensors, and that of the images that emerge from a larger-sensor camera like a DSLR (Digital Single-Lens Reflex).  The number of megapixels is not that important, especially if you’re taking pictures mainly for the internet.  The common standard for images in print publications is 300 dpi (dots per inch), while you need considerably less than that to produce a great looking image on a computer monitor. Perhaps more important than the number of pixels on your camera’s sensor is the quality of those pixels. With the larger sensors of DSLR’s you can make the pixels larger, which makes for lower noise in the final images.  However, all these discussions aside, there is one factor that I think makes more difference than anything else in the perceived higher image quality of DSLR’s and that is the control over DOF (depth of field) that they give you. Put in layman’s terms, a DSLR makes it much easier to exercise some control over what parts of the picture are in, and what parts are out, of focus.  You can even control how out of focus they are. With a compact camera, almost everything is in focus.  This is good when you want everything to be in focus, but terribly frustrating when you don’t. With a DSLR, if you want very selective focus, you just open your lens aperture up to something nice and big, like f2.8, or even bigger if your lens is capable of it and you’re brave.

Why would depth of field make a difference, especially to pictures of radio and electronic parts? It doesn’t if your only interest is purely seeing how things look and how they go together, as in kit assembly instructions, for example. However, when we look at things in real life, we don’t look at everything – we concentrate on the things in our field of vision that interest us. The things that don’t interest us are not necessarily out of focus, they’re just not there (to our brains anyway).  The selective focus of a camera with a larger sensor can approximate this by throwing the things that are not central to the main purpose of the picture, out of focus. Occasionally, I have employed this technique in a rather extreme fashion. One or 2 of the pictures of my K2 build were like that, but I think the technique is more effective when it’s subtle. As an example, I’d like to offer up this photo of an air-spaced variable capacitor that turned up in the mail this week:

The background is moderately out of focus. If you look closely, you’ll see that the vanes of the capacitor are also very slightly out of focus. The front part of the capacitor is in focus, and so is the rule. Because the capacitor vanes are only slightly less sharp, there is no loss of detail, but this slightly limited depth of field helps to make the picture look natural and appealing (in my opinion). The fact that that the subject is a Millen 50pF air-spaced variable capacitor with ceramic end-plates and what looks like silver-plating is an important factor in the appeal too!

Another issue that is very, very important when you’re attempting to take good pictures is lighting.  When I say a “good” picture, I mean one that achieves what you initially set out to do. I don’t know much about how to control lighting for photography indoors.  If you don’t have flash, studio strobe lighting, reflectors, snoots, diffusion panels and all the other lighting gear that many serious photographers have, there is a quick and easy fix that will help a lot – go outside and take your pictures either out in the open if it’s overcast, or in the shade if it’s sunny. What you need is bright diffuse light. Direct light creates a lot of contrast and you don’t want that, because cameras can’t handle it. Photographers spend a lot of time controlling the contrast in their photographs, so our best defense is to look for lighting conditions that don’t create that contrast in the first place. I love bright cloudy days because it means that I can take pictures for my blog pretty much anywhere outside.  If the sun is out, I gravitate to a place in the shade that is still fairly bright.

Even when you’re photographing on an overcast day, the light does still cast shadows – they’re just not as distinct.  There may be certain parts of your project than need a bit more light so the viewer can see the details (especially the innards) so try and orient it so that a little more light gets into and illuminates the parts where you want viewers to be able to see details.

One more thing about light and this is really getting a bit esoteric, but late morning and early morning light has a special quality. The above photo of the variable capacitor was taken early in the morning. The sun had only just risen and there were some very weak diffuse rays of early morning sun lighting the capacitor. See that very slight warm coloration on the metal parts? I think it’s gorgeous but I wouldn’t go out of my way for that. I just happened to be taking photos for the blog at that time.

It’s important to really pay attention when you’re taking photographs. Make sure you get everything in the frame that you want your viewers to see, and don’t include anything that you don’t want them to see. That leaf or bit of dirt lurking behind your project – get it out of the way. It’s much easier to move these things at the time than erase them in Photoshop afterwards. Also pay close attention to the angle from which you take your photograph. Do you want the final image to show a certain detail to the exclusion of most others, or are you trying to give the blog-reader a good overall view of what your creation looks like?  If you make a habit of always asking yourself what the purpose of your picture is, then it sets the stage for the next step, which is doing what is necessary to have your picture achieve that purpose.

Many of my pictures are taken with the project at an angle and with the subject of the photograph not exactly in the center of the frame.  The reason I often orient the object at an angle is because I’m trying to give you an overall feel for what it looks like. If I just show you the front panel, you don’t get a sense of how deep it is.  The reason for not always putting the subject slap-bang in the center of the frame is more of an aesthetic one; I just think it looks nicer. If the foreground of the picture is a blurred piece of ground, and the project is set off-center, a bit further back, and is sharply in focus for example, I think that this helps to draw the viewer into the frame.  I could be wrong; this is all just opinion.

When you’re taking pictures, take your time and take lots from different angles. Don’t be afraid to lie on your tummy and get really close. This thing you’ve just built is your pride and joy and you want to show it off in the very best light to your online readers. If you’re using a DSLR, experiment with different apertures, so you can see the effects of different depths of field on the final image. I spend quite a bit of time crouched low down and lying on my stomach on the ground looking at my projects through the lens of my camera from different angles.  It’s fun.

Here are my bullet point suggestions for good home-brew blog photography:

  • If you have a DSLR (or other camera with a larger image sensor) and know how to use it, this should (IMO) be your camera-of-choice
  • If you don’t have a DSLR, use whatever camera you have
  • Take your pictures in bright diffuse lighting (unless you’re experienced with studio lighting). Outdoors on an overcast day works well. If the sun is out, look for the shade. The idea that only sunny days are good for taking pictures is a hold-over from the time of cheap film cameras with fixed (and small) apertures that, combined with the medium to slow speed films of the day, needed the bright light of a sunny day to get an image at all. Nowadays, sunny days are not your friend (unless you have the lighting tools to control the high contrast that direct sun causes);  bright overcast days are, as well as bright shade on sunny days.
  • Explore your subject – your home-brew project in this case, from different angles, both close-up and from a slightly further distance.  Shooting down from directly above might be the best way to show the layout of components on a circuit board if your main aim is show people what stages and components go where.  Pay attention to what aspects of the project you wish to display in each shot.  Take your time and enjoy looking at your creation through a lens.

Enough about photography, and back to my new preoccupation – air-spaced variable capacitors. Todd VE7BPO has a great page on his site about building VFO’s.  He has details of a very stable Vackar VFO for 40M with which he achieved a drift of the order of 5Hz/hour. That is about as good as you can get with a free-running VFO, and it’s a pretty astounding figure.  If I could get 10Hz/hour, I’d be pretty happy, and I’m thinking that the variable capacitor pictured above (which I got from an eBay seller for $12.50) might do well in this VFO. Here it is again:

I’m a novice on the finer points of variable capacitors for VFO’s but the fact that this Millen 21050 has 2 ceramic end-plates makes for a nice stable construction – more so than the ones whose frame is a single piece of metal bent in a u-shape. The vanes appear to be silver-plated (I don’t know if and why this is a good thing). I don’t know what metal the vanes are made of.  Brass is the best as it has a lower temperature coefficient than aluminum, which is a more common material for variable capacitor vanes. There are no bearings.

Another contender for a VFO could be this one, which was part of a care package of parts from a very generous ham:

The ham who sent me that variable also sent me this one  (this picture featured in an earlier post on the DSB80) :

I also received this variable capacitor, reduction drive and mounting bracket from The Xtal Set Society this last week (the candy and copy of The Xtal Set society Newsletter was also in the package):

It’s great to find a supply of new reduction drives (I don’t know of too many). The air-spaced variable capacitors are also new and while they are not the very highest quality in terms of mechanical stability and Q, there are many uses I can think of for them.  Even for non-critical VFO applications I think they’d do OK – they have to be significantly better than the polyvaricons which are used in some VFO’s nowadays.  It’s a single gang 365pF with a built-in 8:1 reduction drive, which has a nice smooth action.  The actual maximum capacitance is closer to 390pF.  I’d quite like to make a broadcast band regen with this little fellow – or perhaps a direct conversion receiver for 160 or 80M. The neat thing is that the mounting bracket in the above picture is specifically designed to hold the reduction drive at the right height for their variable capacitors, making the mechanics of connecting it all together a lot easier.

Here’s one more photo of the little beauty:

There has been some progress on the DSB80 this week – more on that in a future post.



  1. Hi Dave—thanks for your write up. You made some great points. Looking at your photos; although you light with soft, diffuse lighting, I still see a little directional/specular light in some photos; something I like.
    100% diffuse lighting sometimes gives a milquetoast effect. Occasional infusion of mid-tones, some shadows, highlights, reflections and so forth pump up a photo’s appeal over and above running the aperture open a bit to reduce depth of field in order to generate some nice blur/bokeh. Your point seems to be – good photos are mostly created by skill and effort. I agree. For me, the hardest task in digital photography is not to blow the highlights.

    You avoided discussing lenses (likely on purpose). From my adventure, it’s no lie that good (read as ‘often expensive’) glass makes/breaks photos. For general purpose circuit photography (not macro) I prefer prime lenses at a focal length of 50 mm in full-frame and 35mm in APS-C sensor DSLR cameras (1.5 X 35mm = a FL of 52.5mm on the APS-C). For macro work, I prefer 60mm prime macro lenses, but on the APS-C sensor that puts you up to 90mm for shots like this one (I aggressively lit this one with a small softbox flash and likely over lit):

    Another technique you apply that I like is that you mix it up. Not unlike listening to CW though narrow band-pass fitters, photos that all look the same fatigue the viewer. Photography is a great sub-hobby to building stuff –another set of experiments. My current lighting goals are to exact a lot of mid-tones to garner nice color in my shots; time consuming work that often requires white + colored reflectors, flags and scrims — all while controlling the color temperature. But worth it when the occasional photo actually turns out as expected.

    Keep up the good blogging Dave
    73, Toddly

    Comment by 7BPO — June 21, 2012 @ 4:01 am | Reply

  2. You’re right – I didn’t mention lenses, and although it wasn’t a conscious decision, I think there was some logic to it. I was aiming to describe how I take my blog photos in a way that can be applied by the average ham radio blogger (if such a person exists!) Pictures in most ham radio blogs are fairly straightforward snapshots, taken without too much thought about lighting and composition, so I figured a few simple pointers would help a blogger to elevate his pictures beyond that level if of course, he’s interested 🙂 Too much information might be counter-productive.

    Having said that, a few comments on lenses wouldn’t have gone amiss. My preferences are similar to yours. I went from owning 6 or 7 lenses to the 2 that I use the most. They are a 50mm f/1.4 and a 24mm f/1.4 and on this blog, the overwhelming majority are taken with the 24mm f/1.4 (not a cheap lens but a good one). I purposely didn’t mention brands as for this purpose, brands of camera are, IMO, not important (I notice you haven’t mentioned brands either.)

    A lot of the lighting qualities that lend my pictures a bit of extra interest aren’t particularly planned – they are happy accidents. As you know, it’s pretty hard to achieve 100% directionless diffuse lighting when you’re shooting outdoors, even under heavy cloud cover. I just arrange things so that the soft shadows fall in the best places. Much of this is done instinctively, so I have to think quite a lot in order to put it into words and even realize that I’m doing it. Same thing with the specular highlights – they’re hard to avoid when you’re photographing shiny things, so it’s lucky that they look nice!

    You put a lot more effort into your pictures than I do with mine. I’ve seen the one you linked to before and I love it! As I mentioned, I never came even close to mastering the art of using artificial lighting, which is why I opt for the standard “get outside on a cloudy day, or in shade” solution. For any blogger who isn’t too good with studio-style lighting, it’s a simple solution that seems to work well.

    The 7MHz Vackar VFO on your site may very well be the next project here. I’m thinking of moving my current project, the DSB80 TX/RX, to 40M and want a stable and clean signal to drive it. Truth is, I’m looking for a reason to build that VFO! When I sit and listen to the beat note of my home-brew VFO’s on my K2, I can hear fairly small freq variations and they drive me mildly potty. Giving a guy with OCD tendencies the ability to measure things is a recipe for trouble…… 🙂

    Todd – your site is a source of much inspiration. Thank you!

    Comment by AA7EE — June 21, 2012 @ 5:45 pm | Reply

  3. Hi again Dave. Thanks for the compliment.

    Some great points – what you wrote about finding “perfect” natural light rings true. Although, every once and a while – we find some magical soft light and rejoice.

    I carry a cheap, light, battered and discontinued DLSR (has a Sony APS-C sensor) with a 35 mm lens as my main digital street camera. When the light is nice, it takes nice pictures:

    http://www.qrp.pops.net/images/2012/misc/July 24, 2011-2.jpg …. AVRO Lancaster bomb-aimer’s Perspex.

    Wow – you own a couple of fast lenses with that 24 and 50 mm: My lenses aren’t that expensive either; just sharp lenses I’ve had the good fortune to discover and was smart enough to hang onto. I too, keep a 24 mm, except that it’s just a 2.8….. But it’s the sharpest lens I’ve ever put on my cameras at any aperture. I’ve never used it for circuit photography though – I’ll give it a try.

    The Vackar VFO stands out, but the temperature stability was realized by just following “the rules”, dumb luck and also I happened to own the 1 cap that perfectly balanced the negative and positive temperature drift in the tank circuitry.

    In 2011, I built a 7 MHz Hartley VCO that drifted 3 Hertz in 1 hour – again the trick was to spend days toiling to kill the drift and finally after almost giving up, I conquered my ultra-low drift (at room temperature) VCO goal. Now, I’m looking to PLL circuits for that chore and completed a few preliminary experiments this Winter.

    Best regards,

    Comment by 7BPO — June 22, 2012 @ 2:30 am | Reply

  4. Dave,

    Thanks for doing this blog. I was surprised to read that you don’t use a complicated set-up, artificial lighting etc; and delighted to realise that I have the means of doing the same.
    Please keep on providing your interesting articles.


    Comment by Mike - VK1OO — June 22, 2012 @ 9:59 pm | Reply

  5. It looks asthough the Xtal Set Societ ihasgone incommunacato. Impossable to get through to them. Anyway you have written this piece about Airvariable capacitors which I have a question about. I like making crystal sets a’la early 1920’s. I mean I make everything myself, and in the style of then. As to publications and plans , I would like to know more about slide and book style, like the Crosley one. I have built several book style ones using blank printed circuit copper plates and they work pretty well, Next project is makinga slide one where the movable plate slide goes back and fourth in front of the other. I frame them in either oak or maple and Verathane them, which is both beautiful NS STABILASES THE WOOD. aS MUCH AS i CAN WITH MY WAY OF CHECKING THE Compatence they are pretty close to what is needed. It would be nice to have info about then, etc. The only thing I know is from the pics ofa dismembered and broken Crosley book one . And I have a loop antenna kit with a cheap aluminum slide one. Why aren’t more of them used . Thanks John

    Comment by John of Vermont — March 18, 2016 @ 9:45 pm | Reply

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