Screw In Close Up Lenses... Thoughts?

[CP140]

I was doing some tidying and found a couple of my 1980's vintage "close up lenses". These are the filter style that screw onto the front of the lens. Any advantage to hanging onto them (keeping in mind I have Sigma 70mm macro)... or should they join the Polaroid and the HP 2MP P+S in the "recycle" pile?

[Inkanyezi]

As you have a macro lens, there is hardly any use for closeup lenses.

Those lenses are most useful as a complement to a telezoom, for someone who has one and would not invest in a macro lens, so someone might have use for them. Closeup lenses are also a nifty complement to a bridge camera, as those mostly don't focus very close at the tele end.

[rpcrowe]

If I wanted to increase the image ratio of any macro lens beyond the 1:1 ratio, I would not opt for a "close-up filter" but. rather an extension tube which will allow closer focusing. An extension tube will not degrade the image as could a close-up filter. However, you may find that the lens to subject distance of a macro lens + extension tube is too close to effectively shoot. This is particularly true when shooting little creepy crawlies.

I have a 77mm "no-name" close-up filter which I purchased on a whim at my camera club's used gear sale. t was exceptionally cheap at under five U.S. Dollars. I purchased it to try with my 300mm f/4L IS lens for travel close up shooting on my trip to Alaska. I ended up never using it except for this very quick and dirty test:

This is what I got using the lens alone (the 300mm f/4L IS lens has fairly decent closeup MFD)...


This is what I got when adding the close-up filter to the 300mm f/4L IS lens...


I did not experiment comparing the shots with the close up filter against shots with the bare 300mm lens cropped to the framing that the close-up filter gave me.

I don't shoot very much with the close-up filter because I have a Tamron 90mm f/2.8 Macro lens. But, If I were traveling again with my 300mm f/4L IS lens, I would consider bringing this "el-cheapo" filter for occasional close up capability at little weight and at virtually no cost.

BTW: I have not tried the filter with my 400mm f/5.6L lens. One of the drawbacks of this lens is its long MFD.

Note: Canon sells a 500D close up filter which is supposed to be fairly decent.

[Hero]

I have a +1 and a +2 from B+W for use on my nikkor 70-300. For me they are opportunity lenses for when I'm out and about in the field and suddenly see something small like flowers or bugs (size bees and beetles), worth taking a photo of. It' s quicker than mounting another lens and prevents dust getting into camera/lens while swapping lenses. IQ isn't too bad as long as you stay below 200mm (that's partly due to the nikkor which gets quite soft above 200mm), but not as good as the achromatic ones or a dedicated macrolens. With a price-tag of around $40-50 they aren't as expensive either.

[CP140]

Thanks for your thoughts gents... I might as well hang onto them... perhaps I'll set up a test and see what results I get.

[xpatUSA]

. . . found a couple of my 1980's vintage "close up lenses". Any advantage to hanging onto them (keeping in mind I have Sigma 70mm macro)... or should they join the Polaroid and the HP 2MP P+S in the "recycle" pile?

I bought one for my Sigma 70 macro and then a Raynox DCR-250

www.raynox.co.jp/english/dcr/dcr250/indexdcr250eg.htm

Not surprisingly, the Raynox gave better images, but I'm keeping the close-up filter in case the Raynox ever needs a boost.

[jcuknz]

The simple answer is that the 'macro' lens has its limit and the CU lenses will enable you to get a bit closer. But in practical terms that bit will be a very small bit and probably the loss in IQ from adding more glass will more than equal the loss from cropping slightly.


The advantage of the CU lens is that it can permit the use of a long lens at closer than normal distances so you use the small angle of view of the long lens to achieve tight framing instead of going in close.

Taking first a 50mm lens which focuses to 1:1 ... that means at closest you have a 20 dioptre focal length ...adding a +1 or even a +4 CU lens gives a total of 21 or 24 .... not much difference .. better off IMO without them You would need to be adding a 10 or 20 dioptre lens to make a big difference and the IQ from such a lens is likely to be drack, an exception to that could be a LF camera lens of say 7 dioptre focal length which is a quality lens in itself ... if you have one lying around like I just happen to have You could also add a reversed 50mm camera lens [ 20 dioptre ] though likely it will vignette due to it being smaller than the camera lens as even my f/1.4 50mm lens does and the camera lens doesn't have a sufficient narrow angle of view to see through it. Two similar problems in the exercise. the 7 dioptre f/4.5 LF lens is quite a lump of glass but likely would not work on a fast and long DSLR lens without vignetting .. works nicely with a bridge camera.

Now a 420 lens [ zoom] which focuses normally to 2 metres [ 0.5 dioptre] you add a low powered 2 dioptre [ x2] close-up lens and we have 2.5 dioptre focusing 1000/2.5=400mm or about sixteen inches but from 16 inches you have a tight framing from the 420 zoom's narrow angle of view. [ 2 dioptre more likely to maintain IQ than more powerful lenses ]

Incidentally there is no difference in depth of field with the same framing of the subject, just a perspective difference, whatever focal length you use ... so the greater DoF of the shorter lens is countered by it having to get in closer for the same framing..

Sorry for this ramble but I like and use CU lenses and played with various options over the years.

[xpatUSA]

Sorry for this ramble but I like and use CU lenses and played with various options over the years.

Interesting examples. I did think that "diopter" was simply 1/focal length(m)? But I then saw the term "diopter focal length" so now I've become unsure . .

[Inkanyezi]

Interesting examples. I did think that "diopter" was simply 1/focal length(m)? But I then saw the term "diopter focal length" so now I've become unsure . .

It's actually very practical to think about focusing in diopters, as it gives you an idea of the range in which you can focus when you have a close-up lens attached. Say you have a telezoom that focuses down to 1.2 m, and the lens itself is about 20 cm long from the sensor. Then its close distance corresponds almost exactly to +1 diopter. The conclusion then is that if you put a +1 lens on it, its far distance becomes one metre from the edge of the lens, and the close distance 50 cm from the edge of the lens. With a +2 diopters lens, distances for focusing correspondingly fall between 50 cm and 33.5 cm from the lens. If you have a lens as the most common kit lens, that focuses down to about 30 cm, it corresponds to +4 diopters, and there is really not much idea to complement it with a close-up lens, because strong lenses degrade quality quite visibly. Some kit lenses are a bit longer and focus down to 45 cm only, but at a larger focal length than 55 mm, and their close distance corresponds to about 3 diopters. Hence they may have use for a close-up lens of +3 diopters, preferably achromatic, providing a working distance of between 33 and 18 cm, and close-up lenses of +1 or +2 diopters are pointless with such a lens.

[xpatUSA]

It's actually very practical to think about focusing in diopters, as it gives you an idea of the range in which you can focus when you have a close-up lens attached . . . . With a +2 diopters lens, distances for focusing correspondingly fall between . . . .

Thanks Urban,

It does indeed become clearer if I say "dioptric distance for focusing" instead of "diopter focal length".

So, a 70mm macro lens is about 14-diopter. And my close-up lens is 10-diopter. Together they become 24-diopter which can then be said to have a close distance of about 1000/24 = about 42mm. Is that correct?

[Inkanyezi]

Thanks Urban,

It does indeed become clearer if I say "dioptric distance for focusing" instead of "diopter focal length".

So, a 70mm macro lens is about 14-diopter. And my close-up lens is 10-diopter. Together they become 24-diopter which can then be said to have a close distance of about 1000/24 = about 42mm. Is that correct?

Probably not correct. The dioptric focusing range is its working distance, i.e. distance from lens to subject at its shortest focal distance.

A 70 mm macro lens might be focusing by extension or it might be inner-focused. Most modern macro lenses are inner-focusing, effectively changing focal length instead of increasing lens to sensor distance. A 70 mm lens that focuses by extension alone to 1:1 would extend 70 mm and get a focusing distance of 28 cm, which corresponds to about +7 diopters focusing range.

An inner-focusing 70 mm lens would have a focal length of 35 mm when focused to 1:1 at 28 cm distance, effectively having 14 diopters of focusing range.

In those cases the "diopter" calculation is impractical, and you shouldn't put a 10 diopter lens on it, unless you want the fringing and soft-focus effects that you'd get with a +10 close-up lens.

Actually, a +10 closeup lens is fairly useless, except when you want the effects it provides, as it has all kinds of optical defects one could think of, all of them clearly visible.

I have tried various concepts of closeup lenses, and found the best ones to be achromatic lenses, when they are more than +3 dopters. Even a +3 single lens has chromatic aberration to a degree that is not negligible, but it is easily corrected in software. All closeup lenses however have other defects, coma and curvature of field. Simple lenses up to +3 diopters and achromatic up to about +6 diopters work fine for general photography closeups, where flat field is not necessary, but they are not good enough for reproductions of stamps or similar, as curvature of field and/or chromatic aberration makes them soft as well as distorted away from the centre of the image. That is the primary reason why they work best with small angles, as a tele lens. Achromats of +2, +3, +4 and +5 are readily available, from Canon and from Dörr, and I have scavenged +6 achromatic lenses from binoculars.

For a macro lens, if you want larger reproduction, it is better with extension tubes.

There are instances where closeup lenses are invaluable, as for example with a bridge or compact camera that does not focus close at its longer focal lengths, but only in the wide angle end of the zoom, and then at a very short distance, close to the front element. Often those cameras focus down to about 1 cm, but only at the wide angle end. If a closeup lens can be attached, closeups can be taken at any focal length, providing far more versatility and large reproduction scales at convenient working distance. Also for a tele zoom, they are a good complement for closeup work as flowers, insects and other objects down to a field of view of about the size of a postage stamp, but not an actual postage stamp, as field curvature is unsuitable for flat objects.

[jcuknz]

There is always a way to attach a close-up lens even if one just cellotapes it to the camera. For my first digital camera, a cooli-cam, I ac'd a couple of plastic bits on the front of the camera to hold the scrap of plastic reading glass I used as a CU lens. The camera was of course fixed focus and the addition enabled me to get sharp close-ups

It was used for illustrations for the club magazine I was editing and after being reproduced by photo-copying the usual defects were not that apparent.

One of our members made this marvellous model for his son who was mad on the motion of locos. Andrew Quick.
I think I would have cleaned it up with MS Paint in those early days ... today I am intrigued by the shadow I achieved edit ... just checked the original and I didn't! I had a rough plain background and since there is a flash shadow on another I guess it wasn't the cool-i-cam but my next camera the Canon s20 and I may have had PSP by then.

[Inkanyezi]

Been there, done that. The image below is my Canon PowerShot G7 with a +3 lens attached (scavenged from 1€ reading glasses), glued to the cutout bottom of a medicine canister that is drawn over the tube of the lens. The image is taken with the same camera in a mirror and just flipped in PP.



Later I conceived something a bit more permanent and versatile, that did not need touching the lens tube, which could make the camera shut off. I adapted a piece cut from a plastic drinking glass, to which I glued the rim of a filter, so I had a filter thread to which I could screw any closeup lens. The contraption is put into the tube for a wide angle attachment that is put on the outer bayonet around the lens.



And here's an image taken with two stacked +6 achromatic binocular objectives, totally +12 diopters, of a small flower. To the right in the image the millimetre marks of a steel tape measure are seen, to give an idea of the size. Depth of field is very shallow, so rather little of the flowers are sharp in the image. As can be seen, the chalice is about two millimetres long and somewhat less wide.



And on my Panasonic Lumix G1 I also used a closeup lens occasionally. This miniature rose is taken with a Carl Zeiss Sonnar 85 mm and a +1 closeup lens. The Sonnar focuses down to 1 metre, so the +1 fills the gap down to about ½ m from the lens.

[jcuknz]

Thanks Urban,

So, a 70mm macro lens is about 14-diopter. And my close-up lens is 10-diopter. Together they become 24-diopter which can then be said to have a close distance of about 1000/24 = about 42mm. Is that correct?

I would suggest that if the macro works by extension the 70mm lens at 1:1 is actually a 7.14 dioptre lens in considering further adjustment by extension tube or CU lens. I have been picked up by others that though while it seems a 'practical' way to think as Urban kindly suggests becuase of the different way modern lenses work it is not true in practice, even though the end result is. To me and how I think is based on the operation of a simple lens in a bellows camera with no tricks of optical design being considered. And NO too to the suggestion of dioptric distance for focusing versus diopter focal length ... but then as the renowned NYT wordsmith said 'words mean what I mean them to mean' Innitially I am describing the focal length of the lens in question in dioptres and normally I then talk about the focusing distance in inches or millimetres.

Remembering the point that a 50mm lens becomes a 100mm lens at double extension and all the ramifications of that

[Inkanyezi]

Well, it's like in the song "Man Piaba", it's clear as mud, but it covers the ground.

[xpatUSA]

I would suggest that if the macro works by extension the 70mm lens at 1:1 is actually a 7.14 dioptre lens in considering further adjustment by extension tube or CU lens.

. . . . . .

Remembering the point that a 50mm lens becomes a 100mm lens at double extension and all the ramifications of that

Yes, my Sigma 70mm extends 57mm from infinity to 1:1 and focuses at distance of 257mm from the image plane at that magnification. It has "floating focusing" whatever that is.

But the terminology used in this thread is becoming more troubling:

I really did like the bellows analogy :-) but was floored again by that phrase "diopter focal length".

So, talking the thin lens + bellows analogy:

Is a "50mm lens" one where parallel rays from afar focus at 50mm behind it?

Is a "50mm lens" focused at 1:1 still a "50mm" even though the distance to the image plane behind the lens has doubled compared with say a 1:1000+ magnification, or does it somehow become a "100mm lens"?

If I use a 10-diopter thin lens at 1:1, do I have to scratch the "10" off the side and replace it "5"?

Does the unit "diopter" refer to an invariant value (for a non-zoom lens) or does "diopter" refer to a variable number which depends on the lens' usage?

The only definition I've read for dioptric value is 1000/f where f is the focal length in mm. That would make it invariant.

[jcuknz]

From your description the Sigma is not a 'simple' lens and is using both internal and external adjustment to achieve 1:1 or what with a simple lens would be double-extension.

In my book the 50mm lens is one where light from infinity is focused 50mm behind the lens [ where you measure that from is another aspect which I never consider.]
Double extension is twice that distance and the 50mm lens has become a 100mm lens for purposes of calculating the effective aperture. It remains a 50mm lens but has to be treated/considered a 100mm.
I understand a dioptre to be measurement used by opticians and a one dioptre is 1000mm... so as a definite quantity/measure other distances can be measured by it and expressing them in terms of dioptres. a metre is 1000mm and a kilometre is a thousand times a '1000mm' ....I guess the 50mm lens could be called a 50md lens

A 10 dioptre lens has a focal length of 100mm at infinity focus and at double extension [ 1:1 ] has a 200mm focal length which could be called 5 dioptre.

So YES the dioptre is a definite distance but fractions of it and multiplications of it can be described as 5d or 0.25d ... when I buy my hobby glasses at the store I have a choice in 0.25 stages between 0.5d and 3.25d.

I guess I am giving you a way of using the dioptre as a descriptive term which your reference doesn't. I cannot remember seeing it used this way but it seems a logical use of the term to describe what is happening. I doubt if I originated it

[Inkanyezi]

Of course it is impractical to use the dioptric analogy of focusing distance when we approach larger scales, but it is indeed practical as long as the extension of the system is negligible and we can use the term as the opthalmologist/optometrist does, for dioptric correction. And for distances longer than 10 times the focal length of the lens it is practical. A 200 mm lens that focuses down to one metre by inner focusing has reduced its focal length by remaining the same physical length, effectively acquiring the same result as if we put a closeup lens on it. If we focus it to 1.2 m, and the lens extends 20 cm from the sensor plane, the focusing has accomplished the same as if we put a +1 diopter closeup lens upon it. It is a very practical way of seeing it when we want to know whether it is useful to put such a lens on it. We can clearly see, that an 18-105 mm lens that focuses to 45 cm and extends about 15 cm from the image plane has a focusing power comparable to a +3 diopters closeup lens.

Hence to evaluate what closeup lenses make sense, this way of seeing it is practical. We can see that such a lens may be complemented with a +3 diopters achromat in order to double the reproduction scale, and that closeup lenses of less power than +3 are useless. Also, a bit more pragmatically, we can see that using a +5 diopters achromat, which takes us to a working distance of 20 cm, might be optimal, as it covers reproduction scales that are larger, but at a closer and less variable distance, but where adjustment of reproduction scale is easily accomplished by zooming. The span of working distance can be calculated from the +3 power of the lens focusing mechanism and the addition of the +5 lens, i.e. +5 to +8 diopters or between about 33 and 13 cm from the lens.

So maybe the terminology is limping a bit, but it is a practical way of understanding within what range you can have the AF of the camera fine tune focus.

And I still regard the closeup lens primarily as an upgrade for an existing telezoom, in order to take small objects. The juggling of diopters is to understand what closeup lens you need and makes sense, and within what range of distances it will function.

So the focusing mechanism has a focusing power that can be compared to a dioptric value, which is the same as the working distance, i.e. distance from the subject to the front of the lens. Using a closeup lens of that diopter value or stronger may make sense, particularly for a lens with a narrow field of view, a narrow angle, i.e. a tele lens. The longest distance with that closeup lens attached is the same as its focal length, i.e. 1/diopter_value. The closest distance will be the combined diopter values of the closeup lens and the dioptric equivalence of the focusing power for normal close distance.

[jcuknz]

There is a possibly interesting practical aspect that whereas normally the focus of a camera lens is measured from the sensor/film plane and marked with a circle and horizontal line through it on the outside of the camera, the close-up lens is measured from the front of the CU lens ... as Urban and others have aluded to but not spelt out as I am here

Trouble is focusing scales are largely absent with modern lenses

[Inkanyezi]

I see it as a purely practical issue. First evaluating what closeup lens might make sense for your lens. Hence if you have an 18-55 mm lens that focuses to 28 cm, it is impractical to add any closeup lens, as the lens itself has a "focusing power" that is maybe five to six diopters, as at 28 cm the working distance is perhaps 20 cm or less from the optical center of the lens. Adding a closeup lens of less power accomplishes little and is a waste. Adding one of the same or more power will degrade image quality and take you to an unpleasantly close distance, with little margin of fine tuning by AF. So adding a closeup lens to the most common kit lens is not a very brilliant idea.

On the other hand, with a longer focal length, as the 18-105 that focuses to 45 cm, the focusing power is +3 diopters, and adding another three does make sense, as it can double the scale while still staying at a reasonably large distance. Or if you have a tele zoom of 55-200 that focuses down to 1,1 m, which corresponds to +1 diopter, a lens of +1 will let you work between about 1,15 m and 65 cm. On a tele, a +1 closeup lens will not degrade image quality noticeably, and stabilisation is still fully functional, just as when you use the lens at a larger distance without any closeup lens. So the combo will probably be more comfortable for shooting insects than a macro lens without stabilisation.

And the calculation of the focusing power in diopters is practical for knowing within what range you can get a sharp image. With a piece of string attached to the camera, just as long as the far distance, and with a knot at the close distance, it is easy to find the right distance and let AF do the fine tuning. These calculations indeed have practical aspects. And once you know those two distances, you won't need the distance scale. The close limit of the lens is often written on it but at least it is in its specs, and it is all you need to know to calculate within what range AF will help you get sharp images.