The thread that you linked to was concerning one lens reversed and mounted to another. There is exposure factor to be considered.
The original thread in this case was concerning diopter or close-up lenses which is not the same thing at all.
I guess to be more correct in my response the statement should be "there is no APPRECIABLE light loss with diopters.
Originally Posted by John Koehrer
As I understand it, a reverse coupled lens behaves exactly like a high power diopter the value of which is 1/(focal length in meters). So a 50mm lens is a +20 diopter instead of the +2 or so of the usual canon or nikon dual element ones, but otherwise there is no difference. I don't understand why there should be an "exposure factor" like a filter.
Does anybody here actually take macro photos or do we all sit around and talk about it?
Seriously, you do not need to correct for bellows extension when you use a diopter. Get a TTL metered camera, a lens, a diopter, some extension, and see for yourself.
Here's some examples of one that prints critically sharp at 8x12". Nikon F3HP, AI 80-200/4.5 Zoom-Nikkor, Provia 100F, Nikon 3T diopter.
All taken with diopters and for convenience I normally use my incident meter so I didn't have TTL metering making corrections for me. Trust me, try a decent set of diopters with a telephoto zoom and you'll be sold on the technique too.
The comment about working distance is on the money. Working distance is increased with higher focal length and as already mentioned, diopters effectively shorten the focal length of the lens. Same goes for lenses with floating elements like the micro-Nikkor 105/2.8. The older 105/4 uses straight extension and has longer working distance.
Last edited by Mike Kovacs; 10-21-2006 at 09:57 AM. Click to view previous post history.
Very nicely done images and well stated comments. Much appreciated.
Good. Now that I know what gear to buy, I'll go out and buy some tubes, diopters and even a camera with a TTL meter and make some photographs instead of talking about it.
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Vivitar Close Up teleconverter
Originally Posted by Anupam Basu
To add to the possibilities....
I have this very interesting option that I use that sort of combines some of the above, and would be worth your consideration for close up purposes.
I found (on Ebay) a Vivitar Close Up teleconverter for use with my Olympus OM cameras.
It is a 2X teleconverter, that offers adjustable close up capability.
It is sort of like an adjustable close up diopter, that goes between the camera body and the lens.
It probably is closest in results to the close up filters, but it offers adjustable magnification, open aperture metering, and good results.
I used it in the closeup of the front of my old Six Sixteen Kodak that I posted in the Medium Format Folder thread here:
IMHO, it really leads to relatively effortless making of good quality photographs, at a cost much less than the macro lenses that yield the best quality.
Matt, I have that TC and quite like it. Thanks for suggesting it.
I also have several diopters - single and dual element, tubes - auomatic and manual, and lenses from ordinary macro to enlarger and cine lenses. And yes, many cameras too - with and without TTL metering both small and large format. And I do use them for macro photography, more than many people.
So my point was that asking me to buy a camera sounds a litle condescending and will not change my argument that effective aperture and effective focal length being equal, tubes and diopters need the same exposure for the same magnification.
Originally Posted by MattKing
Sorry, is that directed at me? Who told anyone to buy anything? I have dozens of perfectly exposed colour transparencies taken using a diopter, and a handheld meter. How can that be explained? One does not properly expose transparencies by dumb luck.
Originally Posted by Anupam Basu
Again, my experience with diopters does not agree. I see exactly what you are saying, but is there something else going on that you haven't considered? E.g. when you mount a diopter the effective focal length decreases - what of the aperture? I would expect the marked f/stops to open up, since the size of the diaphragm has not changed.
Not an authoritative treatment of macro photography but if you refer to Shaw's Closeups in Nature, he is sitting in my camp.
Thanks for that response. That is more reasoned and addressing the problem at hand. I apologize if my reply sounded testy, but I do appreciate a discussion of this issue rather than the claim that anyone who has really shot closeups would know this. I think all of us have had experience with the setups under discussion and know what a TTL meter is - so given that, we can try to figure out the problem of differing claims
I too, shoot tranparencies and since many of my reversed setups don't have auto diaphragm control, I calculate the effective apertures beforehand and then expose by eye or with an external meter. So far, my exposures seem to have been spot on too.
I think your point about effective focal length is the key here and I mentioned it in my last post - with effective focal length changing, effective aperture will change too. So when using either diopters or tubes the aperture set on the lens means nothing. Unless one calculates the effective apertures and focal lengths one cannot compare the two setups. Another thing that diopters will change is the pupillary magnification value of the lens and that contributes to how the effective aperture is calculated.
As for John Shaw, I am aware that he says diopters don't lose light. If you see the Bjorn Rorslett post I pointed out earlier in the thread, Rorslett too attributes this to Shaw and claims that it is a mistake on his part. I haven't found Shaw's claim in either Lefkowitz or Blaker, FWIW.
If I have time, I will do some tests this winter. The way I think of it, though, is that the diopter isn't collecting any more light than the lens on a tube when you think in lux (light intensity - or light per square area). So it can only achieve magnification by spreading out that light to cover a larger area as in my enlarger example above. So for a given magnification, the degree of the spreading out needs to be equal regardless of whether that spreading out occurs by moving the source further away (air itself doesn't absorb any significant amount of light, far less than glass in fact) or by interceding a glass element to bend the light. In fact, the above TC example as a kind of diopter behind the lens can illustrate this. A 2x TC needs two stops more or 4 times more exposure because it enlarges the image 4 times.
I see you are using the F3 too. Great camera but a pity about the spot meter. I use it with the DW-4 6x finder and meter externally too. So we agree on that