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Sigma 500mm F7.2 APO

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2 20,069 Sun December 31, 2017
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100% of reviewers $177.50 8.00
Sigma 500mm F7.2 APO

Compact (worlds shortest refractive 500mm!) ultra telephoto launched according to this archived page in 1990, in both MF and AF versions (pentax mount only in MF??). Apochromatic and low dispersion lens elements, internal focus IF, tripod collar with foot and carry strap buckle, hood.
KA mount has a ricoh pin, but it is the harmless rounded variety. Note that on a Pentax DSLR with the aperture ring in "A" position, the lens registers a wide open aperture of f8 on the displays, not f7.2.
Note too that sigma lenses from this era are a bit notorious for having the "non-slip zen" body finish that deteriorates with age and becomes sticky. Meths/denatured alcohol/iso-propanol/similar can clean it off.
Scan of original sigma brochure here.

Filter Size: 72mm
f/Stop Range: F7.2-45
Iris: 6 blades
Minimum Focus Distance: 12' (3.5m)
Magnification 1:15
Angle of View (full frame): 5 Deg.
Groups/Elements: 9/12
Length (hood not extended): 23.3cm/ 9.4"
Tripod mount, with a buckle to attach a carry/support strap
Maximum Diameter : 8.4cm/3.35"
Weight ~1.1kg/ 2 lbs 8.7 oz

Bob Atkins has a good page comparing 500mm mirror to 500mm refractive (Canon) and discussing the pros and cons.
Sample Photos: View Sample Photos
Mount Type: Pentax KA
Price History:

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Site Supporter

Registered: November, 2012
Location: North Wales
Posts: 2,434

1 user found this helpful
Lens Review Date: December 31, 2017 I can recommend this lens: Yes | Price: $130.00 | Rating: 8 

Pros: Compact, pka, "most compact refractive 500mm", good iq, excellent value (can be acquired opportunistically at a bargain price due to eg deteriorated zen)
Cons: "Zen" coatings become sticky, difficult focus (handling 9/10 for size and weight, 6/10 for twitchy focus), can suffer from hazed cemented optics
Sharpness: 9    Aberrations: 8    Bokeh: 8    Handling: 7    Value: 10    Camera Used: K5, NX20    New Or Used: Used   

My impression is there aren't many of these old sigma 500mm f7.2's around. The original spec is impressive: 12 elements in 9 groups with 3 LD elements, USP of "smallest non-reflex 500mm" (that's my tamron 500mm mirror behind for comparison) and the indicated price bracket is of prosumer proportions.
However these have the infamous disintegrating "zen" rubberised coating that was a sigma "thing" at that time. Yep, that's sticky!

However the more the coating is deteriorated the easier it cleans off with meths/similar - see pic above, post cleaning. Only trouble is the distance scale and other markings come off with it. A post in this thread on suggests using an artists spray fixative (update - which is what I used later, taking off the adhesive tape you can see on the lens in the pic above).
This lens certainly is relatively light and compact compared to other 400mm and 500mm MF lenses I have tried, indeed positively casual compared to eg my SP 31A 200-500mm adaptall zoom, , but it's still not a lightweight. It has a useful strap attachment point by the foot of the tripod mount so that it can be carried without the camera/mount taking the strain. Both the built in hood and TM are good, however the TM isn't quite at the balance point - distinctly front heavy, and more so with lighter cameras like my mirrorless NX20.
I am quite favourably impressed with the performance of the lens - images are sharp and well corrected, the only fringing I have noticed has been a few pixels wide PF in some backlit circumstances. But focus is really ticklish, due to that base f7.2 (I really notice increased difficulty by eye through an OVF as lenses get slower than f5.6), and the really short focus throw on this IF lens - only ~ 135 throw to cover from 3.5m to .
Test crops f7.2, f11, f16 - samsung NX20. I was looking for good performance straight from f7.2 and I can suggest that the lens delivers.

Pentax K5, mostly f9, varyingly cropped, resized.

Samsung NX20.

Some more birds at a feeder, samsung NX20.

This image showed some more significant CA - purpling seeping into the head and neck of the tit. Ameliorated with fringing tools and reducing purple luminence and saturation in LR3.

1:1 pixel peeping crop of a mallards head. At 800ASA the NX20 is much noisier than the K5, but the underrlying resolution is quite good.

If you want 500mm then this is a very good option. As a 500mm I would give it 9/10, in fact I can suggest this might be the best price/performance M/F 500mm on the s/h market, based on typical prices it goes for. It's certainly way better than those long "wundertute" 500mm f8's, and I would overall put it ahead of my tamron SP 500mm mirror. Particularly stopped down to eg f11 the images (bokeh) are smoother and contrastier and more pleasing, and the slighly larger depth of field helpful, even if the sharpness is not that much greater. But 400mm alternatives are likely to be easier to use/focus - I get constently better results witth my FD 400mm f4.5, or my adaptall 300mm f2.8 + 1.4x tc, hence the 8/10. That faster nature of those optics makes more difference than any reach gain 500mm vs 400mm/420mm. But the sigma has a particular cachet as a value grab-and-go, fits in my camera bags lens pocket, option. Let's face it, to really make the next level you're looking at 10-times-as-much four digit prices for a 500mm f4.5, or, even s/h examples of sigma x-500mm zooms will be much more, without really offering anything much more in IQ or speed (but AF).
New Member

Registered: February, 2012
Posts: 4
Lens Review Date: May 27, 2013 I can recommend this lens: Yes | Price: $225.00 | Rating: 8 

Pros: Well Built,Smooth Focus,Auto,Fair Close focus
Cons: Focus Scale
Sharpness: 8    Aberrations: 8    Bokeh: 8    Handling: 8    Value: 8    Camera Used: Pentax k5II    New Or Used: Used   

Before getting this lens read reviews that went from Rubbish to really quite good . Not sure what my final conclusion will be but I'm getting there ! It's heavy - needs a neck strap on the tripod mount .
This lens is often criticised for being 'not sharp' . It's certainly not the sharpest lens in the world but the length(rotation) of the focusing scale does not help . The interval 7m-Infinity is 30mm , 100m-Infinity 6mm. (On an old Ensinor 400mm 7m-Infinity is 85mm , 100m-Infinity 17mm ). Focussing this sigma requires a lot of care . DOF approx +/- 1.5 Foot @ 100 Foot - That looks about 8/1000 inch of focus rotation ! I'm currently trying to develop the best technique based on the focus indicators and viewfinder image. I think manual focus will be quicker ( and more accurate ) than the autofocus version would have been .It's also criticised for being 'Slow' , but a loads of modern lenses are barely half a stop faster - modern sensor technology ( reasonable results at 1600 asa+ ) and the pentax in-camera stabilisation make this (almost) irrelevant . In UK daylight the viewfinder is bright enough for most situations on the Kr. To keep this really steady resting on a wall or fence-post with a beanbag or 'pod' is good.

This was at about 50-100 feet

And this about the minimum focus ( 12 Feet )

Thought it time to update this ! Weight could be worse! Sharpness upgraded for 2 reasons...Some of the marking down was really due to it being a touch out of focus - The compressed scale make focusing very tricky and the optimum stop seems to be f11 , so it's only focussed a stop over the taking aperture.
Some of the sharpness marking down was really due to a UV filter ( Slight but there - A mixture of it being a new filter and imperfect focus leading to coming to wrong conclusion ) Filter will be staying off ! Again the better the focus it's easier to see that the aberrations are better controlled.

The following processed from DNG in rawtherapee - ( Exposure adjusted by defaults , no sharpening )

The following processed from DNG in rawtherapee - ( Exposure adjusted by defaults , sharpening by RL Deconvolution Radius 1.5 - rest defaults )

The following I think show's indications of sharpness ant the minimum focusing distance ?
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