Discussion in 'Lens Matters' started by PMurrell, Apr 14, 2015.
Anyone had experience of this combo? If so - any sample images?
Not sure what you are after. Extension tubes come in different lengths to achieve different magnifications so you need to say which tube. The cambridge in colour website has a calculator which shows the magnification/ minimum focussing distance.
Was thinking of trying macro shots of flowers, possibly insects.
Extension tubes tend to come in two main varieties. Those with the electrical connections, and sometimes mechanical linkages, to achieve full autofocus and autoexposure, and those that are basically just straight tubes, with no coupling between the camera and the lens.
The simpler tubes are a lot less expensive, but obvious require manual focus, and working out the required expsure can be a bit of a faff - the tube effectively extends the focal length, so for a given size aperture, you get a higher f/number. Also, many auto diaphragm lenses (almost everything made in the last ~30 years) have a sprung loaded diaphragm, which will stay at either maximum or minimum aperture - I'm pretty sure the 50/1.8G is like this. Some lenses have a manual aperture ring, and I believe there are some extension tubes with some form of aperture control.
Another option for relatively inexpensive macro is a supplementary close up conversion lens, which screws on the front of the main lens like a filter. These vary from the very cheap uncoated ones on Amazon, which give pretty bad distortion, chromatic aberration, and edge softness (sometimes centre softness isn't too hot either), to the the better quality, but more expensive ones from Raynox or Marumi, that have multi element achromatic construction, and good coatings, and can be fairly sharp in the centre, but still tend to be a little soft and distorted in the corners.
The main advantage of the close up lens is that all the autoexposure and auto focus systems work normally.
The G lenses lack an aperture ring so they require tubes which either allow mechanical linkage through the tubes to the aperture control arm or have some other mechanism for closing the aperture. If the tubes lack this then the lens will default to minimum aperture - great for DoF but hopless for focussing.
I suspect that for use with extension tubes a secondhand 50mm F1.8 D lens with aperture ring may be a better bet.
Thanks all. Think I'll save for a used macro lens.
Probably the best option, in terms of both ease of use and image quality.
The Tamron 90mm f/2.8, in all its various forms, seems quite well regarded (I'm pleased with mine, earlier non-stabilised version), and often turns up second hand at reasonable prices. The 90mm focal length gives a reasonable working distance (from front of lens to subject), which is helpful for shots of live insects etc. - shorter focal lengths sometimes make it hard to get light on the subject because of the shadow cast by the lens.
Sigma's 105/2.8 is also reputedly very good (I believe it's what AP use for the test chart shots in camera tests), as are the various Nikkor 105/2.8s, though these tend to be pricier.
By all means save for the ideal bit of kit but have some fun in the mean time.
Close up lenses to use like a filter are not that bad. For printing even A4 they are not bad.
Another possibility which is actually very good indeed provided you have the self discipline to not push the rules is to use a ring which reverses one lens in front of another. The idea is that light from every point in the subject is collimated between the two lenses. The lens fitted directly to the camera must be focussed on infinity and its diaphragm is used to set the aperture. The second lens has the aperture set wide open. The distance between the flange of the supplementary lens and subject is about the same as the distance between that lens and sensor if it was in normal use. The setup gives a constant magnification. Turning the combination round on the camera gives a reciprocal of the magnification but severe corner shading may result.
As usual SRB Gritum is the source for the connecting ring.
P.S. The second lens not even need to be a Nikkor; even an M42 £29 Pentax SMC Takumar prime is not even ok but excellent.
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