Sigma 20mm f1.8 EX DG ASPHERICAL RF 

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out of 5
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out of 5
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Lens Summary

Overview

Wide Lens
20mm f/1.8 EX DG ASPHERICAL RF

Wide angle lens with large aperture and superior peripheral Brightness

This super-wide-angle lens is ensured minimal light-fall-off with superior peripheral brightness. The iris diaphragm has 9 diaphragm blades to obtain beautiful out of focus images in the foreground and background. This is an ideal DG lens optimized Digital SLR camera.

- - -

Minimum focus distance of 20cm
The minimum focusing distance of this lens is 20cm and it has maximum magnification of 1:4 with fast F 1.8 maximum aperture. The minimum focusing distance of 20cm and 94.5 degree Angle of view allow close up photography surrounding the photographic subject.

Handling
The lens incorporates Dual-Focus (DF) mechanism. It is easy to hold the lens, since the focusing ring does not rotate during auto-focus, yet it provides adequate focusing torque of the focusing ring during manual focusing of the lens. The rear focus system eliminates the need for the front of the lens to rotate, thus allowing the use of a "Petal-type hood", which is superior light blocking effect.

Incorporated aspherical lenses
The use of Aspherical lens elements in both of the front and rear lens groups effectively compensates for distortion, Spherical aberration and astigmatism.

Lens Construction
 
13 Elements in 11 Groups
Angle of View
 
94.5 degrees
Number of Diaphragm Blades
 
9 Blades
Minimum Aperture
 
F22
Minimum Focusing Distance
 
20cm
Maximum Magnification
 
1:4
Filter Size
 
82mm
Dimensions
 
Diameter 88.6mm X Length 89.5mm
Weight
 
520g
SRP
 
£349.99

20mm f/1.8 EX DG ASP RF
 
SIGMA
   
CANON
   
NIKON (D)
   
SONY
   
PENTAX

Lens Specifications

Generic Lens Specifications
Lens Type: Prime
IS / VR / OS: None
Min Focal length (mm): 20
Max Focal Length (mm): 20
Number of Elements: 13
Element Groups: 11
Max Aperture: 1.8
Minimum Aperture: 22
Diaphragm Blades: 9
Closest Focus Distance (m): 0.2
Maximum Magnification: 1.4
Filter Diameter (mm): 82
Diameter at widest (mm): 89
Lens Length (mm): 90
Weight (g): 520

Details


 


 

 

20mm f/1.8 EX DG ASP RF
Lens Hood
Fitted Padded Case
Front and Rear Caps
Instruction Manual
1 Year Warranty Card
2 Year Extended UK Warranty Card

Price Tracking

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User Lens Reviews

Average user rating from: 9 user(s)

Overall rating (weighted)
4.2
Sharpness
4.0
Build Quality
4.4
AF Speed
3.9
Value for Money
4.6
 

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0 of 0 people found the following review helpful

Can't beat this one for the price, Friday, 17 October 2008


Overall rating (weighted)
4.8
Sharpness
5.0
Build Quality
5.0
AF Speed
4.0
Value for Money
5.0
Well built, well damped MF, solid all around, great Contrast and color, sharpness is fine at 1.8, maybe a Bit better than my Sigma 24-70/f2.8 at 2.8. I didn't notice serious light fall-off around the corners. At 1.8 it is soft around the corner as comparing to the center. But for the price and focus length, otherwise would be a miracle. This lens at 1.8 (wide open) seems to be more grainy than my Canon 50/1.4 at 1.4 and 100/f2 at f2.

AF is on par with my other non USM/HSM lenses, both speed and noise wise. For now this lens complete my primes for indoor low light use. I am a hobbyist and have no stomach for $$$$ L lenses. But I do notice that the only L I have - 70-200/F4L produces superior IQ/Contrast/Color consistently, comparing to the rest of the crowd. But this lens certainly performs good enough for my purpose. I did use Sigma 10-20 and Sigma 24-70, Sigma 17-70 for lanscape shots. The results are good for 10-12 prints. Flaw usually becomes apparent when zoomed to the original size on screen (I use a 27"). I expect this Sigma performs similar results.

Also, a small piece of good news: this lens has a front cap like Tamrons (rather than Canons) - you can pinch and hold the cap around the center rather than around the brim. This is very helpful with the hood on. This new design is great but the material used seems to be less solid than the older ones. But I really appreciate this change. On some of the lenses, I just have to remove the hood before I can do anything with the cap, very awful in the field, especially when you are in a hurry... Thanks, Sigma!

Bottom line - a great low light wide angle lens for crop sensor cameras if you are a hobbyist like myself.

I have a film camera I rarely use. Will update this when I do with this lens. But I don't have high hope there, considering the price.
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0 of 0 people found the following review helpful

Can't beat this one for the price, Friday, 17 October 2008


Overall rating (weighted)
4.8
Sharpness
4.0
Build Quality
5.0
AF Speed
5.0
Value for Money
5.0
Well built, well damped MF, solid all around, great contrast and color, sharpness is fine at 1.8, maybe a bit better than my Sigma 24-70/f2.8 at 2.8. I didn't notice serious light fall-off around the corners. At 1.8 it is soft around the corner as comparing to the center. This may partly due to the fact that when focused close at f1.8, the DOF is rather shallow.

Just did some quick AF test on a tripod shooting a ruler at 45 degree angle from 5' to 1' distance, AF are spot on! But the IQ is clearly better at the center when focus closely. At 5' f1.8, the IQ isn't great anywhere. Will try this lens on a better body (maybe 5D MkII) in the future to make sure the low IQ at farther distance wide open isn't caused by the sensor on my 40D, because low light shots are more taxing on the sensor.

For the price and focus length, otherwise would be a miracle. This lens at 1.8 (wide open) seems to be more grainy than my Canon 50/1.4 at 1.4 and 100/f2 at f2. But it is usable for me as a hobbyist for sure. Though there is nothing to be bragged about. IQ gets a lot better stop down at all distances. So I am glad I don't have the AF problem heard so often online. I did similar test on my other lenses, Canon as well as Sigma/Tamron. Some do have AF problems, front, off-center, back, you name it. Zoom is worse than prime of course. So I am just glad this Sigma is not one of them.

AF is on par with my other non USM/HSM lenses, both speed and noise wise.

For now this lens complete my primes for indoor low light use. I am a hobbyist and have no stomach for $$$$ L lenses. But I do notice that the only L I have - 70-200/F4L produces superior IQ/Contrast/Color consistently, comparing to the rest of the crowd. But this lens certainly performs good enough for my purpose. I did use Sigma 10-20 and Sigma 24-70, Sigma 17-70 for landscape shots. The results are good for 10-12 prints. Flaw usually becomes apparent when zoomed to the original size on screen (I use a 27").

Also, a small piece of good news: this lens has a front cap like the Tamron's (rather than Canon's) - you can pinch and hold the cap around the center rather than around the brim. This is very helpful with the hood on. This new design is great but the material used seems to be less solid than the older ones. But I really appreciate this change. On some of the lenses, I just have to remove the hood before I can do anything with the cap (e.g. Sigma 170-500, or Canon 70-200), very awful in the field, especially when you are in a hurry... Thanks, Sigma!

Bottom line - a great low light wide angle lens for crop sensor cameras if you are a hobbyist like myself, especially for subjects near by at close distance.
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0 of 0 people found the following review helpful

OK for the price, Friday, 17 October 2008


Overall rating (weighted)
3.8
Sharpness
3.0
Build Quality
4.0
AF Speed
3.0
Value for Money
5.0
Not great wide open, barely usable at low light. But still, something is better than nothing. Canon 50/f1.4 is far better wide open. But I can't get much of a shot sitting across from a restaurant table, there this Sigma comes to rescue. This lens is otherwise well build. Just that I wish it's better wide open. 1.8 is so much better than 2.8. In regular household light, 2.8 is not very useful unless the subject is completely still. I kinda expected this lens not to be sharp at 1.8 wide open. But indeed it isn't. For the price, I can't complain too much. Happy shooting.
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0 of 0 people found the following review helpful

Not bad, but not great, Tuesday, 12 August 2008


Overall rating (weighted)
4.0
Sharpness
4.0
Build Quality
5.0
AF Speed
3.0
Value for Money
4.0
Tried three copies of this lens. Great specifications. Nothing else is this fast at this width and this price. The image is acceptably sharp wide open, but only just -- definitely nothing like Sigma 30mm 1.4, which beats this lens hands down in everything but the width.

Good lens if you are a photojournalist and need to print small images at low Resolution. Then pixel sharpness doesn't matter much. But if you are a pixel peeper, beware.

The lens is well built, and looks great, but the motor is noisy and I assume eats up camera batteries.

By far the worst thing about this lens is unpredictable focus, which I encountered on all three copies. None of the copies had any distinct front or back-focusing issues, when focusing on paper. Three out of five times they were spot on. Then they would back or front-focus with equal probability. And yes, I know all about the Depth of field and this was not a factor in my tests. And my Sigma 1.4 does not behave like that. As this is an older lens, I think there may be some occasional issues of lens-camera communications that don't exist in the newer 1.4 30 mm.

The bottom line is, I am keeping the first copy of the lens. With all the deficiencies this lens has, I couldn't find any other options at this price. I guess with this lens on, I will have to take more than one picture of everything to make sure I got the shot.

Sigma, how about a newer APS-C version of this lens? Please?
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0 of 0 people found the following review helpful

Superfast wide angle at affordable price, Tuesday, 08 May 2007


Overall rating (weighted)
4.5
Sharpness
4.0
Build Quality
5.0
AF Speed
4.0
Value for Money
5.0
This is my fifth Sigma lens, and I couldn't be happier with it. Because of it's f/1.8, don't expect much depth of field when shooting wide open. Especially in close ups, that's the trade off for low light capability. This lens has opened up a whole new world of possibilities for me with indoor photography when a flash is inapppropriate (performances, candids, etc.). The wide angle is not so extreme that I have to deal with distortion at the edges, but in close ups it creates a different perspective on the subject, especially with faces. I also own a 10-20mm zoom which I use primarily for architectural shots, but this is my go-to lens for landscapes, group portraits and low light situations.
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0 of 0 people found the following review helpful

Great budget wide lens with f/1.8, Monday, 09 April 2007


Overall rating (weighted)
4.8
Sharpness
5.0
Build Quality
4.0
AF Speed
5.0
Value for Money
5.0
This lens is definitely not a Canon L-series lens so don't expect perfection with it. I bought this lens used mainly for the wide frame and incredibly low fstop and I'm very happy with it. It's a great lens for the money.

I usually only travel with my Canon XTi/400D and Canon 50mm f/1.8 budget lens, but I've really needed a wider lens for getting everything I want in my frames. This lens is perfect as my walk around lens for any available light in night or day.

For my travels where I can only take one backpack, I may be restricted to only taking the tiny 50mm f/1.8. But whenever possible, I will take this Sigma 20mm f/1.8 wherever I go.



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0 of 0 people found the following review helpful

Absolutely fabulous images, Thursday, 13 July 2006


Overall rating (weighted)
5.0
Sharpness
5.0
Build Quality
5.0
AF Speed
5.0
Value for Money
5.0
I've had this lens for three years. It takes absolutely wonderful portraits. If you want to see someone as you have never seen them before, take a full frame portrait shot of them using a Canon 10D or 20D with this lens. Gorgeous.

The lens rounds out such shots just slightly and really enhances facial features. The effect is almost like a very mild fisheye. I have used this to create some of the most compelling captures of the human range of facial expressions that I've ever taken.

Highly recommended product. Stunning clarity. John Kahrs was wrong in his review. Either he had a defective lens or he has some sort of disability that kept him from using it correctly.

This Sigma lens is an excellent value compared to similar Canon lenses, although both brands are of high quality, in my experience.
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0 of 1 people found the following review helpful

AMAZINGLY SHARP AND FAST SUPER-WIDE ANGLE, Sunday, 07 May 2006


Overall rating (weighted)
5.0
Sharpness
5.0
Build Quality
5.0
AF Speed
5.0
Value for Money
5.0
I have used this lens extensively with the 1D and the Rebel XT. Results have been excellent. My suspicion is that the previous reviewer got a defective or damaged copy of the lens. It is incredibly sharp, even at f1.8, which I did not expect - generally you expect a lens to be a bit soft wide open, especially 1.8. The degree of sharpness of this lens is quite surprising.

I have used, for example, both the Canon 50mm f1.8 and the Canon 35mm f2.0, both of which are deservedly renowned for their sharpness and contrast. I find this lens to be sharper than either of them wide open. The lens provides images which have excellent color saturation and contrast. Of course, at f1.8, depth of field is razor thin, by design, which is great for bokeh or out of focus background, but which also requires care concerning the desired focal point being in focus. Speaking of bokeh, I find it to be very attractive compared to any other lens I have used.

Its minimum distance focusing is also quite remarkable. I think it is rated at just under 8 inches, but I routinely focus at distances which seem a good bit closer than that. The lens works well as a macro for many applications, with a relatively strong multiplication factor.

Of course, given the inherent light-gathering of a 20mm focal length lens, combined with a huge aperture of f1.8, this lens is outstanding for shooting indoors or in other low-light situations with natural light and no flash.

Canon's nearest competitor to this lens is the 20mm f2.8, which is a full stop slower in terms of light collection. I consider this lens to be an extremely good value at the retail price, new. If you can get a good copy used on-line, it will be an incredible value. You may find that you never want to take the lens off the camera because of its versatility as a walkaround lens.

This lens has been extremely well-reviewed, by and large, on lens forum sites. I encourage you to check those out. Most people rate the lens 5 out of 5. A distinct minority give it 1 out of 5. I suspect that they either have defective copies which may need repair, or they have inaccurate perceptions of the lens. Also, popular photography magazine online reviewed this lens, as well as the 24 f1.8 and the 28 f1.8, very highly.

I would highly recommend this lens to anyone who wants a fast, sharp superwide angle lens.
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0 of 0 people found the following review helpful

Sounds good on paper . . ., Monday, 28 February 2005


Overall rating (weighted)
1.5
Sharpness
1.0
Build Quality
2.0
AF Speed
1.0
Value for Money
2.0
I'm amazed at how inferior this lens is. It looks good. It feels good, and I like the focus clutch mechanism. The specs are great and just what I wanted for my EOS 10D: a wide, fast, fixed focal length lens. I had never bought a third party lens before.

Images from this lens plagued with bad detail, poor contrast, and the out-of-focus areas are harsh and filled with unpleasant artifacts. I never think twice about bokeh, whether its bad or good, but this is bad. I kept waiting for something decent to show up but it didn't. The situation improves when then aperture is stopped down, but wide open this lens is abysmal (and wide open is what I got it for). Perhaps it is defective, but I doubt it.
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