Featured A new piece of kit for coin photography....

The 1:1 adapter for the Bokina is actually not just an extension. It has optics inside, thought I am not sure exactly what they do. I don't think it's a 2x teleconverter but somehow it allows the 1:2 lens to achieve 1:1.

The XS is a very good camera for coins. It is what I recommend to folks looking to buy a camera for coins. Even though it's only 10MP vs 18MP for the T2...5 series, that's not a huge limitation. This is because you will rarely publish a full-size image, so some level of down-sizing is almost always done. I recommend at least a 2x down-sizing to minimize sensor aberrations. I also recommend integer downsizing to maximize downsize quality. For the T5, you would likely downsize a factor of 4x, from 5184x3456 to 1296x864. A crop to 864x864 or perhaps 800x800 gives an optimum size for web publishing. For the XS, downsizing the 3888x2592 by a factor of 3x yields the same 1296x864 image. So the difference between the two cameras is either downsizing by 4x, or 3x, to yield a publishable image.

One other difference between the cameras is the Diffraction Limited Aperture, or DLA. The XS, with fewer pixels in the same size sensor, has a wider pixel pitch. This yields a smaller DLA versus the T5. For the T5, the DLA is f6.7, so any aperture smaller than that will start to show effects of diffraction. The XS has DLA of around f10, so is more forgiving of stopping-down the lens to get best DOF.

 

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Whoops! Looked through the manual and saw that the 1:1 adapter for the Bokina has 3 lenses in it, so it's more than an extension tube. They do pop-up on eBay for not too much.

I'm learning a lot from this. Thanks so much.

Cal

 

Not to mention "effective" aperture changes with increased magnification as well, pushing you closer to DLA. Effective Aperture is Aperture * (1 + Magnification) so that if you're using 0.5x magnification and set aperture at f/8 on the lens, you're actually getting 8(1+.5)=f/12. And you're into diffraction. At 1x mag, like you'd use for a Dime or Cent, you'd be at f/16.

And it's unlikely you can get the whole face of a coin into sharp depth-of-field with apertures wider than f/5.6....

 

Interesting great write up! What type of light do you use?