I think the point is that for a single shot with the usual RGB filter in front of the light sensors, the light intensity and colour at each pixel position must be calculated as an average of surrounding pixels in order to get the contributions from all 3 colours (RGB). Pixel shift improves on this by taking successive images with different filter colours (RBG) at each position so the calculation at each pixel is from RG and B at the same position (i.e. not averaging over adjacent pixels). Removing the usual RGB filter also removes the need to average over adjacent pixels so has a similar effect to pixel shift but, of course, it's only for mono not colour. Importantly, though, it does not need multiple exposures for a single image so does not have the pixel-shift problem of subject movement between successive pixel-shifted shots. The overall effect will (should ) be better handling of grey shades than a single shot with RGB filter because of the absence of averaging. Whether most of us would notice the difference is another thing entirely...

Steve

That definition of a FL is only true if the image is actually in focus. The way I think about it is to imagine a beam of parallel light rays entering the lens. When the beam leaves the other end of the lens it is converging to a point of focus behind the lens (it's what I used to do as a child with a bright sun, magnifying glass and combustible paper :twisted. The focal length is the distance between the optical centre of the lens and the point of focus. It's a property of the lens and exisits whether of not there is a capture medium behind the lens.

The add-on lens on its own also brings a beam of parallel rays to a focus. So when the main lens is put behind the add-on, the beam is already converging when it enters the main lens. Add the convergence from the main lens to the already converging beam and the point at which it converges to a point of focus behind the main lens is closer to the rear of that lens than in the absence of the add-on lens. Thus, the focal length of the combination is less than that of the main lens on its own. I'm pretty sure that the mathematical formulae for this sort of thing was covered in A-level physics, but that was a looooong while ago !

Steve

The focal length of the lens isn't changed, of course, but the camera now has two lenses in sequence and thus SR needs to take into account the focal length of the two lenses in combination. It's the same as wearing glasses or contact lenses - the focal length of the eye isn't right, adding the extra lens brings the focal length of the combination to the correct value.

I've found a closeup filter calculator on the Extreme Macro website link. Give it the focal length of the main lens and the dipotre (1/f) of the add-on lens and it calculates (among other things) the focal length of a lens that is equivalent to the combination.

Steve

And it's not just the focusing that's excellent, so is the lighting. Together they give a distinctly 3-D feel to the pictures (at least for me). It's a joy to see them.

Steve

Here are a couple of the better shots from my first attempts with a recently acquired Raynox DCR-250 macro adapter attached to a DA 55-300mm (the original model). The Raynox was acquired as a light weight 'macro in the pocket' capability when I really don't want to be carrying the weight and bulk of a macro lens 'just in case'. More practice is definitely needed - the success rate was much lower than I'd expect if using the Sigma 105mm or Irix 150mm macro lenses - but I think that's just due to different ergonomics. I'm pleasantly surprised at what this relatively cheap add-on can achieve when everything comes together.

Incidentally, the buds are crab apple 'Cheal's Weeping'. There were no buds at all last year. It looks like this year is going to make up for it!

Thoughts, comments etc. welcome as usual.

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Steve

Interesting. The 1.4TC is almost permanently attached to my DA*300. I've sometimes thought that OOF long grass or reeds can look a bit fussy, but assumed that it was the price to pay for using the TC. Perhaps it's due to the lens itself.

Steve

I've recently acquired a Raynox DCR-250 macro adapter for those times when I only want to carry one lens around and don't expect to take macro, but just in case something pops up... Anyway, trying it out for the first time today (with the 55-300mm), it dawned on me that I had no idea what to do about shake reduction. The camera (K3) didn't know that the Raynox was attached so would have been doing whatever it does for the 55-300mm. However, that surely isn't appropriate with the Raynox. So... what should I do if using the Raynox (hand held of course)?

Steve

That is astro - it has to be 'cos Orion is posing above the island. And it's superb, particularly when seen big. .

One tiny niggle from an artistic point of view: that star/planet on the right hand edge is a bit distracting - easy to remove of course.

Steve

No. 3 is top of the list for me - grape hyacinths have never looked so good! And No.2 is close behind.

The OOF branch in the squirrel shot doesn't bother me, it's just the way things are. But it's a pity the squirrel has a grey coat, if only it were red ... .

The lens is obviously a good 'un, but is it significantly different (better?) than the DA*300mm f4 (apart from the slightly smaller max aperture)?

Steve

One of those sights that are easy to miss but impressive if you see it. Those clouds seem almost alive and malign. I like it .

Steve