Close up filters.

[Lee L]

Mr. Koehrer is correct. Lens extension tubes increase the lens to film distance, and so light intensity per square unit of area decreases. However, diopter lenses shorten the lens to subject distance, and do not change lens extension from the film plane, so light intensity per square unit area on the film isn't changed.

If you want to stick with the enlarger analogy, projecting the same size negative with a 50mm or a 100mm enlarging lens, both to the same size final print, will still give you the same light intensity on the paper with the same f-stop.

Lee

 

[Anupam Basu]

Mr. Koehrer is correct. Lens extension tubes increase the lens to film distance, and so light intensity per square unit of area decreases. However, diopter lenses shorten the lens to subject distance, and do not change lens extension from the film plane, so light intensity per square unit area on the film isn't changed.

If you want to stick with the enlarger analogy, projecting the same size negative with a 50mm or a 100mm enlarging lens, both to the same size final print, will still give you the same light intensity on the paper with the same f-stop.

Lee

How is magnification achieved without spreading out the light? The fact that 50mm and 100mm enlarger lenses at the same print size will give the same times just confirms my point that it is the enlargement size of the print and not the distance that matters.

I had the same idea from John Shaw that diopters don't lose light. But Bjorn Rorslett corrected me on another forum and I have since done many tests to confirm his claim. See this thread for that exchange.

-A

 

[naturephoto1]

How is magnification achieved without spreading out the light? The fact that 50mm and 100mm enlarger lenses at the same print size will give the same times just confirms my point that it is the enlargement size of the print and not the distance that matters.

I had the same idea from John Shaw that diopters don't lose light. But Bjorn Rorslett corrected me on another forum and I have since done many tests to confirm his claim. See this thread for that exchange.

-A

Hi Anupam,

The diopters (the Nikon, Canon, and Leica Elpro are 2 or more? elements and do produce very very good to excellent results) have a negligible amount of light loss when mounted on the camera lens. There is substantially less light loss than working with extension tubes, extenders (basically an extension tube with lens elements), or a bellows. Regardless of the conversations on other sites or threads, if you question the small to no light loss of using such lenses just meter with your 35mm or medium format camera through the lens alone and/or through the lens with these diopter lenses attached. That will confirm how little light is actually lost. These lenses allow for much greater working distances than the extension tubes or bellows. I assure you you will see little (perhaps 1/6 stop or so) or no change to your meter reading.

Rich

 

[Ole]

The diopter changes the effective focal length of the lens, so that the same extension gives a higher magnification. The "light loss" is the same at the same magnification, but since the effective focal length is shorter, the effective aperture is larger [/i]at the same setting[/i].

 

[Anupam Basu]

Regardless of the conversations on other sites or threads, if you question the small to no light loss of using such lenses just meter with your 35mm or medium format camera through the lens alone and/or through the lens with these diopter lenses attached. That will confirm how little light is actually lost. These lenses allow for much greater working distances than the extension tubes or bellows. I assure you you will see little (perhaps 1/6 stop or so) or no change to your meter reading.

TTL metering is exactly what I have been using to make my claims. And in my experience extension tubes give much more working distance than diopters with the same magnification.

Ole, that is very well explained. I agree.

-Anupam

 

[John Koehrer]

Anupam,
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.

 

[Anupam Basu]

Anupam,
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.

John,

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.

-Anupam

 

[Mike Kovacs]

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.

 

[naturephoto1]

Hi Mike,

Very nicely done images and well stated comments. Much appreciated.

Rich

 

[Anupam Basu]

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.

-A

 

[MattKing]

Vivitar Close Up teleconverter

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.

-A

Anupam:

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:

(there was a url link here which no longer exists)

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

 

[Anupam Basu]

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.

-A

Anupam:

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:

(there was a url link here which no longer exists)

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

 

[Mike Kovacs]

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.

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.

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.

 

[Anupam Basu]

Mike,

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.

-Anupam

 

[Anupam Basu]

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

 

[Helen B]

Would some example numbers help? A slightly simplified example:

Think of a 100 mm (10 D) lens set at f/8 and focussed at infinity. The rear nodal point is 100 mm from the film plane, and the diameter of the effective aperture (entrance pupil) is 12.5 mm.

Now add a +3 diopter lens, and suppose that it is 50 mm in diameter. Being simple, it has an exit pupil of 50 mm, which is larger than the entrance pupil of the main lens.

Because of the diopter, the lens is now focussed on an object 1/3 m away, ie 333 mm. The combined lens has a focal length of 13 D or 77 mm. The rear node is still 100 mm from the film plane and the object is 333 mm from the front node, so the magnification is 0.3x.

If the entrance pupil diameter was unchanged you might say that f/8 had changed to f/6.2 because the focal length of the lens was now 77 mm – in fact it would be marked as f/6.2 if it was marked for infinity. But the rear node is 100 mm from the film, not 77 mm, so the effective aperture is still 12.5/100 mm, ie f/8. Magic.

In fact the entrance pupil may be larger, because of the magnifying effect of the diopter. It could be about 5% larger, so 12.5 mm would change to 13.1 mm and the aperture would be 13.1/100 = f/7.6. Offsetting that would be the extra air-glass reflection losses, so you could be back where you started from.

If you wanted the same magnification with only the 100 mm lens without a diopter the rear node would be 130 mm from the film plane and the effective aperture would be 12.5/130 = f/10.4 when the lens was set at f/8. If the lens was set at f/6.2, the effective aperture would be f/8.

If you wanted the same magnification with a 77 mm lens set at f/8 with no diopter, the diameter of the entrance pupil would be 77/8 = 9.62 mm and the rear node to film distance would be 100 mm (as above), giving an effective aperture of 9.62/100 = f/10.4

Anupam’s statement that "effective aperture and effective focal length being equal, tubes and diopters need the same exposure for the same magnification" appears to be in agreement with the above simplified calculations. The point is that, in this situation, with a diopter the marked aperture is close to the effective aperture; but with an extension tube with no diopter the marked aperture is not the effective aperture. More or less.

Best,
Helen