Explanations:

* Effective work distances: if the front lens element is relatively deeply built into the lens, a lens hood can seem almost unnecessary; on the other hand, a lens hood is a must if the front glass determines the length of the lens. Since some of these lens hoods can be quite long, they can change the effective work distance. In these cases, ( As can be seen in this column above.) first, the effective distance is indicated, then the length of the lens hood is substracted from the effective working distance (-), and the remaining effective distance as the third number. Since the lens hoods of the 180mm lenses are bulky, one could consider changing them for a smaller type if they effected one's work.

* Canon MP-E 65: the lens can be adjusted within a range from 1:1 to 5:1 (Relative to 35mm film.) Using it on a 1.6 crop camera (Such as a Canon 20D.) 1.6:8X related to 35mm. The indicated work distance refers to 1:1 and/or 1.6:1.

* Sigma 50: Because the working distance at 1:1 magification is so very small, the lens hood, if used, will strongly shade the photographic object, this limits the hood's usability greatly in this mode.

 Sigma lenses:

The 180mm is really durably built, all tubes free from play, it has the most solid lens hood connection of all three 180mm macros. AF speed is poor, despite the ultrasonic drive.

The two other focal length Sigmas are mechanically the weakest of all lenses in the test. The extending tubes have considerable slackness, the 50mm more than the 105mm; their AF speed is the slowest of all, often still "hunting" with back focus tendency. I have the impression that "available steps in focussing" are too large.

The front glass of the 50mm and still more of the 105mm, are quite deeply built into the tube, so they can be used without a lens hood under most circumstances.

 Canon lenses:

The 180mm, as is the 100mm are ultrasonic lenses, the 100mm is very fast, in maximum telephoto mode it is the fastest objective lens in the tests, however not always accurately, which can be partly seen in the test results. Despite the USM the 180mm is very slow, it can be helpful to focus manually to the desired point, then switch to AF and allow this to take over, this way accurate focussing is most rapidly reached. If one starts with infinity, some seconds may well pass until AF kicks in. The MP-E65 illustrated in the center of the photo to the left, is a magnifying lens without AF, the focussing tubes extend tremendously making this easily the longest of the lenses tested when in fullest extended macro mode. All Canons are built very sturdily, in another class to all others, but unfortunately considerably heavier. All adjustment rings work very freely and smoothly and it is of a huge benefit to be able to manually over-ride the AF. Coupling rings for macro flash are integrated alongside the filter threads at the front of the100mm and the MP-E65, the 180mm needs an adapter ring. The Canon plastic lens hoods are the weakest from the range of lenses we have here on test.

Tamron lenses:

Both lenses are made of plastic, which can be seen immediately with the 90mm, whereas the 180mm gives the impression it is more solidly made of metal. Despite it's plastic fashion the 90mm is completely free of slackness. Both lenses have the lowest weight of their class. The mechanical AF is heard clearly, only moderate in speed, but faster than the mechanical Sigma drives. Astonishingly, the outstanding AF accuracy is better than Canon's lenses. To change from AF to MF one slides the focussing ring foreward for AF and backwards for MF; the problem is that in order to do this, one inevitably loses the focus point selected and one then needs to start the procedure of reselection over again, this can be very frustrating. The 180mm Tamron has an additional feature which yet again has advantages and disadvantages. It has an adjustment ring, which can be used to rotate the front filter thread, a big advantage when needing to turn a polarising filter and especially if the lens hood is attached. An example of the disadvantages is discovered when using the Canon MT24-EX Twinflash, in that the two small flash heads will often turn spontaneously, (Always when it's a huge inconvenience!) depending on the angle of one's camera: A locking switch would solve these problems and offer perfection to this feature. The 90mm really doesn't need the additional shade of a lens hood under most circumstances, due to the front element being so deeply embedded in the front tube. On the otherhand, the180mm will need it's very sturdily built lens hood; an additional excellent feature is that the inside of the hood is manufactured with black grooves which reduces light reflection to a minimum.

Results:

The robustness of the Canon lenses is unequalled, although the Sigma 180 and Tamron 180 are also very solid. Canon's plastic lens hoods are very flimsy and seem cheap, this includes the bayonet fittings on the hood and camera, inevitably with time, the bayonets start to break up, resulting in very badly fitted and unsafe hoods: The hoods of all other lenses are clearly better. Both other Sigma lenses feel a little shaky and the tubes have some slackness. The Tamron 90mm looks somewhat cheap due to it's plastic design, but mechanically however it is an excellent lens, which is absolutely free from any slackness between the tubes.

2. Test object: Shown to the right, a Fern Frond. The selected cut-outs are framed in blue. In order to keep the fern frond flat, a normal 35 mm slide frame was fixed to the frond. Some shading of the cut-out at the edges occured because of the slide frame, but has had no effect on the results. With this fern frond, only the 100mm lenses were tested, as explained earlier.

Results:

1. overview: all lenses near the center . 2. overview: all lenses at the margin.   Comment/evaluation: The performance of the Canon MP-E65 is outstanding, it is as good at the corners as it is in the center and at all apertures. The performance of the Sigma 50mm is also outstanding, however this lens' contrast behavior may have gained some benefits from the changed light conditions. (Due to the very small distance from front element to the test object, only 3.9cm, I had to change the position of the lights to avoid shading). This becomes clearly apparent with the colour; nevertheless, optically it is an outstanding lens over the entire image field. Within the row of the lenses around 100mm sizes, the Tamron 90 clearly topped all it's competitors, further, is the remarkable sure-footedness of it's AF. Though the Canon, in this comparison performed better than in the "fern test", it does not reach the quality of the Tamron's AF; it's AF problem can be seen at f=11. The clear loser is the Sigma 100, at the edge images are only usable above f=8, in the center at f=5.6. I even tried it by manual focussing, but didn't get better results. At apertures higher than f=16 all "100's" show a remarkable decrease of performance due to diffraction. Within the180mm row, again the Tamron is king, immaculate from the edge to the center at all apertures. At f=4 the Canon has some weakness at the corner but at f=4 in the center it is perfect. The Sigma is really good in the center at f=5.6, best at f=8, at the edge only good at f=11. Amazingly with the Tamron 180mm as high as f=22 returned some very useable images!.

3. Test: Shown here to the right. The three100mm (Approx') lens tests at all apertures, in the centre and in the corner. Here, there is no doubt over Tamron's leadership in any optical situation.           dramatic improvement of the optical performance at higher magnifications can be reached by use of a high-quality add on lens/macro filters. (Eg: Leica Apochromat for the 2.8/100 Apo macro or the Canon D500 Macro Filters). Therefore all further tests with lenses were completed with a Macro filter attached, please see below.

4. Test: Now using the Macro filter on the lenses, they were adjusted to give the same view as in test 3 above, of approximately 24x36 mm; to do this only a slight extension of each lens was necessary, but now they are able to work in the "optimal range". Shown here are the results for aperture f=6.3 which may well be the most relevant for Macro use. The lowest improvement came from the Tamron which shows just how good it is without the filter! the other two lenses show a remarkable improvement. Using f=8 and above brought all lenses to the same level. The most striking improvement is visible with the crops at the corners, whilst the centres were very good prior to the filters being used anyway. The improvements felt by using the Leica apochromatic macro filter and the Canon 500D macro filter, can be gained by using your own make as long as it is of very high quality. In any case the improvements gained with this method will be superior to using extension/ distance rings as they will extend the lens it's self in most cases, too close to the subject and overextend them to outside their best range specification Now all lenses can work in a fully corrected dimension leading to a great improvement, especially of the lenses, which did not perform so well prior to the attachment being used.

5. Test: Using the Leica macro filter it is possible to reach a magnification of 2.5X. All these test images were done at apertures of f=11 or higher, however the resulting DOF is very small indeed. Again the best results were produced by the Tamron. Apertures above f=16 show a remarkable decrease in quality due to increasing diffraction. NB: Sorry, I lost one picture from the Sigma at f=22, therefore the white gap.

My conclusions: