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Sunday, 1 January 2012

Review: Canon EF-S 55-250mm F/4-5.6 IS


I purchased this lens based on hearing good things said about it, it seemed to offer a lot of ability for the price and was also very small and lightweight making it an ideal for travel or just when you don't want to be weighed down with a bag full of heavy lenses. On paper the lens offers a lot for the money but does it deliver in the real world?



Build quality, finish and operation:

It's not an L lens but it's better made than the kit lens and the 17-85mm lens and even the 17-55mm lens! It feels surprisingly solid with smooth actions and the finish has that mottled effect that Canon is using more often nowadays, it's a small touch but it goes a long way to making the lens look better and feel better in the hand. The zoom ring is nice and big and the lens actually has a decent focus ring too unlike the 18-55mm kit lens which is possibly the worst excuse for a focus ring ever! The lens has a plastic mount but it's a light lens so I have no reason to believe this will cause problems any time soon. For the price I cannot fault the build and finish at all.

The autofocus is pretty quiet for a non USM system and not particularly slow either but accuracy and consistency can be a major issue which I will go into later but I will point out right now that it is this lenses biggest Achilles heel.

The image stabilizer was a brand new design at the time this lens was released and was designed to be cheap to produce but also highly effective and it is certainly that! Canon claim a 4 stop advantage which I'm sure is quite possible if you have steady hands, I have very unsteady hands but I can certainly see a strong advantage with the system activated, another impressive quality for the price.



Image Quality:

Optically this lens is very impressive considering the price, it's unusual for cheap tele zooms to be sharp at the long end especially wide open but thanks to the inclusion a UD glass element this lens manages it and also adds an additional 50mm reach over comparable models, the lens is actually slightly sharper at 250mm than it is as 200mm! This lens is really commendably sharp at 250mm, the edges are somewhat softer at some focal lengths but not terrible, sometimes there appears to be uneven sharpness at the edges of the frame which could be down to the stabilizer rather than decentring but overall, considering the price of the lens the sharpness is nothing less than astounding, you'll struggle to find anything as sharp in this price range by any other manufacturer.

The colour this lens produces seems to be in line with most other Canon lenses and is vibrant and well saturated. Contrast is also pretty good although it fades very slightly towards the long end but it's easily restored with post processing.

The bokeh is another pleasant surprise with this lens, overall it's commendably smooth and when the lens is used wide open highlights tend to be rendered quite attractively. It's not perfect and the aperture is not rounded so out of focus highlights will look somewhat angular when the lens isn't wide open and if you encourage it you can get the lens to produce ugly bokeh but overall it's really quite decent all things considered.

The lens suffers from only very mild chromatic aberrations in the most extreme circumstances and for day to day use it's pretty much a non issue, how do they manage it all at such a cheap price? There has to be something bad right?

Well as it turns out there are a few negatives, which is reassuring because I need every justification I can get for owning the 70-300mm L!

Firstly the lens vignettes like a mofo! The corners are VERY dark indeed when the aperture is wide open which can be very noticeable in some shots, it's not always a big hindrance and at the longer focal lengths subjects tend to be somewhat centralized anyway so it can be a non issue but it's worth mentioning because it is very strong and very pronounced in unfavourable circumstances. Some people don't mind vignetting at all and think it adds to a photo, I tend to agree a lot of the time but I would prefer to just add the effect in photoshop and have a choice! With this lens you will have vignetting if you use it wide open whether you like it or not!

Another issue I have found is that sometimes the image doesn't have consistent sharpness on each side of the image and whilst this could be down to a centering issue it doesn't happen all the time and only seems to occur when the stabilizer is active which leads to my crazy theory! I think the image stabilizer may play a role here because at this price point especially it's entirely possible that the corrective element/s show somewhat higher resolution in their centres than their edges so the harder the stabilizer works the more of the non optimum area of glass will be in use which could result in lower resolution in some parts of the frame, this is more a crackpot theory than fact although edge sharpness does appear to be more consistent when the stabilizer is turned off and it is a fact that the true optical path is interfered with when the stabilizer is active so who knows!

Those two problems although notable are rarely serious enough to spoil what is generally a sharp and punchy lens, what really spoils the party is actually not an image quality issue but something that can prevent you accessing that image quality which is the autofocus!

This lens seems to have a mind of it's own when it comes to focusing, sometimes it's fine and other times I can struggle to get one sharp shot out of a burst of ten! It doesn't matter if you're using AI servo or single shot there just seems to be a lot of inconsistency, I've stood at Cardiff bay with the sun nearly down and achieved good focus lock on speedboats going flat out in both single shot and AI servo mode and then on other occasions something as slow paced as my wife walking towards me at the beach has resulted in the lens missing focus almost every time regardless of focus mode!

Obviously some of this is just down to price, when I failed to get good focus with fast jets at an airshow it was obvious that I was expecting too much from the lens but when you have to take two or three attempts to get a photo of a building locked on you know there's something amiss. It's a pity because the focusing is actually very quiet for non USM and isn't too slow either but in terms of accuracy it's just not very reliable.

It's doubly maddening because a lot of the time the lens will get it spot on and often I sit at the computer going through images and the consistency is great until you get to that one perfectly timed photo that you've been waiting to check out on the monitor since you took it and you realise that was exactly when the lens decided to miss focus! I suppose I may have a bad one but I have heard similar stories from others so who knows?

In overall IQ terms this lens is a fantastic performer for the price but be careful of the autofocus, digital memory is cheap so take a few attempts at each shot and your chances of one being in focus will rise sharply but sadly this doesn't help when you have only a brief opportunity to get the shot where you will just have to hope for the best! The lens gets it right a lot of the time but there's definitely a higher than average failure rate so watch out! I think a lot of the time people just write this lens off as being cheap and soft when they are just experiencing focusing issues.


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100% crop taken wide open at 250mm
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100% crop taken wide open at 180mm
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100% crop taken wide open at 250mm
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100% crop taken wide open at 250mm
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Conclusion?:

This lens has some flaws, it vignettes badly and the autofocus can be unreliable but overall the combination of image quality and build quality and overall performance is exceptional, the fact that the lens is sharp at 250mm wide open on an 18mp sensor is truly impressive, I can't think of any autofocus tele lens with image stabilization that comes close to performing as well as this for the price, it's genuinely unrivalled and represents value for money at it's most extreme!

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