Canon EF 50mm F1.8 II review To πλαστικό Διαμάντι της Canon σε ένα αναλυτικό Review

Μέ κόστος κάτω από 100€ αλλά με εξαιρετικά οπτικά ο prime φακός της Canon χωρίς usm,is και άλλα καλούδια συνεχίζει να προκαλεί να ασχοληθούν μαζί του ,ένα review σε βάθος λοιπόν από το έγκριτο Dpreview.com
Canon EF 50mm F1.8 II review

The Canon EF 50mm F1.8 II is the least expensive lens currently available for the EOS system, and has been in the lineup since late 1990. It's a simplified version of the original EF 50mm F1.8 of 1987 (often referred to as the 'Mark I') which was supplied as standard with some of Canon's earliest 35mm EOS SLRs; however it can trace its lineage back a lot further than that, as the company has been making 50mm F1.8 standard lenses since 1959. Like its predecessor, it uses simple symmetric Gaussian optics with six elements in five groups, in a well-proven formula which is known to offer excellent correction of aberrations.

Although designed as a 'standard' lens for 35mm film, these days the 50mm F1.8 is far more likely to be seen doing service on APS-C format DSLRs, on which it behaves like a short telephoto portrait lens (80mm equivalent). With its remarkably low (sub-$100) price, it tends to attract the interest of Canon SLR users looking to start experimenting with fast lenses for low light and shallow depth of field work, or simply hoping to get sharper results than those which can be provided by the kit lens bundled with the camera body. It's also a potential option for those seeking a near-disposable lens to use in adverse conditions.

Angle of view
The pictures below illustrate the angles of view on 35mm full frame and APS-C camera bodies:



Canon EF 50mm F1.8 II specifications
Street price • $90 (US)
• £90 (UK)
Date introduced December 1990
Maximum format size 35mm full frame
Focal length 50mm
35mm equivalent focal length
(APS-C) 80mm
Diagonal Angle of view (FF) 47º
Diagonal Angle of view (APS-C) 31º
Maximum aperture F1.8
Minimum aperture F22
Lens Construction • 6 elements/5 groups
Number of diaphragm blades 5
Minimum focus 0.45m (1.5 ft)
Maximum magnification 0.15x
AF motor type DC Micro Motor
Focus method Unit focus
Image stabilization • None
Filter thread • 52mm
• Does not rotate on focus
Supplied accessories Front and rear caps
Optional accessories ES-62 hood
Weight 130g (4.6 oz)
Dimensions 68.2mm diameter x 50.5mm length
(2.7 x 2.0 in)
Lens Mount Canon EF only

On the camera


Mount the lightweight, insubstantial 50mm F1.8 on a higher-end EOS bodies such as the 5D and you could almost be forgiven for forgetting that it was even there; this is one lens which won't be a chore to carry around all day. It's perhaps best matched to the small entry-level EOS models such as the 450D, on which it forms a particularly lightweight and unobtrusive combination ideal for low-light shooting.

The lens's handling is best described as functional; the manual focus ring works OK, but you probably wouldn't want to use it all the time. It is also coupled to the focusing motor when the lens is set to AF; this means that it rotates during focusing, so care must be taken to avoid holding it when using autofocus.

Autofocus
This lens uses a very basic micromotor to drive the autofocus, which isn't the best system Canon has ever made. AF performance is overall quite similar to the 18-55mm kit lenses, i.e. a little slow and slightly noisy (although a lot better in this regard than some similar systems we've used, such as the Olympus 50mm F2 macro), however the large maximum aperture does mean that it continues to work happily in much lower light levels before starting to struggle and hunt for focus.

In use, the AF generally works very well in good light, but as illumination levels fall it becomes progressively more hesitant and less reliable. It has a disconcerting tendency to misfocus slightly in low light (most visible when shooting with large apertures) and whilst the camera body's AF system must share some of the blame for this, the EF 50mm F1.4 USM does appear to be more reliable in these situations.

Resolution The Canon 50/1.8 is quite sharp in the centre wide open, but the corners are noticeably soft, and the lens needs to be stopped down to F3.5 when sharpness in these regions is important. Best results are obtained at F5, and beyond this diffraction slowly takes its toll; as usual on APS-C, anything smaller than F16 should be treated as emergency only.
Chromatic Aberration Lateral chromatic aberration is essentially a non-issue (a fundamental characteristic of the symmetric Gaussian design of the lens).
Distortion
Distortion is very low at just 0.4% barrel, which will be essentially invisible in real-world use.
Despite the moderate magnification, image quality is good. The centre is soft wide open but sharpens up nicely by F2.8, with corners catching up at F5.6. There's just a slight hint of barrel distortion, and no chromatic aberration at all.
Specific image quality issues
As always, our studio tests are backed up by taking hundreds of photographs with the lens across a range of subjects, and examining them in detail. This allows us to confirm our studio observations, and identify any other issues which don't show up in the tests.
Soft corners at wide apertures
Not unusually for a full-frame optic used on the resolution-hungry APS-C format, this lens isn't at its best at wide apertures, and although central sharpness is OK the corners look distinctly soft. In this regard it's worth noting that depth of field is very shallow at F1.8, and real-world results are mainly dependant upon focus accuracy, with the slightest relative movement between photographer and subject resulting in a misfocused image. Of course depth of field issues also mean that the corners of the frame are often out of focus at F1.8 anyway.


Canon EOS 450D F 1,8------------------ F5,6


The EF 50mm F1.8 II performs much like any other 'fast 50' on full frame, with pronounced softness across much of the image area at large apertures, but giving truly excellent results on stopping down. It's not quite as good as the EF 50mm F1.4 USM when compared like-for-like (central sharpness is similar but the corners slightly softer), however it's very close indeed.

Resolution

The 50mm F1.8 is sharp in the centre even at F1.8, but the corners (and much of the rest of the frame) are very soft. Corners sharpen up progressively on stopping down, and by F5.6 look very good indeed. The very best performance is at F8, where this sub-$100 lens is a good match to even the EOS-1Ds Mark III's 21Mp sensor right across the frame.

Chromatic Aberration Lateral CA is extremely low, and even on the EOS-1Ds Mark III there's no measurable fringing. There's also only a very slight level of colour blur due to spherical aberration - overall nothing of any real-world consequence.

Falloff We consider falloff to become perceptible when the corner illumination falls to more than 1 stop less than the centre. The 50mm F1.8 II behaves much like any similar lens on full-frame; there's significant vignetting (2.7 stops) wide open, but this disappears progressively on stopping down and is insignificant by F3.5.
Distortion
Distortion on full frame is about 1.2% barrel; just a hair less than the 50mm F1.4 USM, and potentially visible in the occasional shot with straight lines right across the frame (although scarcely problematic, and easy enough to fix in software).

Specific image quality issues
As always, our studio tests are backed up by taking hundreds of photographs with the lens across a range of subjects, and examining them in detail. This allows us to confirm our studio observations, and identify any other issues which don't show up in the tests. We used the lens on both APS-C and full-frame bodies, namely the EOS 450D and the EOS 5D.

Flare
As we've come to expect from large maximum aperture lenses, flare can sometimes be an issue with the 50mm F1.8 II. With it's deeply recessed front element, the lens effectively has a permanently attached hood, and so is generally resistant to veiling flare from light impinging the front element at an angle. However the moment you point the camera towards the sun things can start to go wrong, although on the whole the lens generally seems to fare a bit better than its F1.4 big brother in this regard.


F2 CANON 5D

F5,6 CANON 5D SUN IN THE FRAME
Background Blur ('bokeh'): lots of little pentagons
One genuinely desirable, but difficult to measure aspect of a lens's performance is the ability to deliver smoothly blurred out-of-focus regions when trying to isolate a subject from the background, generally when using a long focal length and large aperture. The 50mm F1.8 can produce substantially blurred backgrounds at wide apertures, a huge advantage for portrait shooting especially on APS-C.
Overall it's a pity Canon didn't implement a slightly more complex diaphragm construction with seven or eight blades, as this behaviour somewhat spoils the performance of an otherwise extremely fine lens.


Chromatic aberration
Lateral chromatic aberration is negligible in our studio tests, and is equally near-impossible to find in real-world shots; quite simply it's not an issue when using this lens. However some bokeh chromatic aberration can occasionally be visible at F1.8-F2.2;

Optical performance at wide apertures
Our studio tests show that this lens is not at its best at wide apertures on full-frame; central resolution is just fine, but the corners are extremely soft and subject to significant darkening through vignetting. However in this regard it's also important to appreciate that with the extremely small depth of field afforded by a 50mm F1.8 lens, and assuming a reasonably centrally-placed subject, the likelihood of any object in the corners of the frame being remotely in focus is in fact minimal, and corner resolution therefore near-irrelevant.

The images below illustrate the lens's performance for those inclined to shoot flat subjects at wide apertures, here using the 13Mp EOS 5D (this is admittedly not the most aesthetic of test subjects, but about as interesting as you'll get when looking for soft corners wide open on this type of lens). Contrast is clearly a bit low at F1.8, and the corners suffer from a combination of low contrast and significant vignetting (although the actual resolution of fine detail isn't too bad). Stop down to F4, and much as we saw on APS-C, the lens produces perfectly good results from centre to corner.

FINALY
Conclusion - Pros

Excellent image quality when stopped down
Essentially no lateral chromatic aberration

Extremely cheap
Conclusion - Cons

Extremely cheaply built
Harsh and distracting bokeh due to pentagonal aperture
Vignetting at wide apertures on full frame (which only disappears at F3.5)
Inconsistent autofocus in low light (most problematic when using large apertures)

Overall conclusion

The Canon EF 50mm F1.8 II may be one of the cheapest lenses currently on the market, but its optics belie its lowly price. As befits a classic standard prime lens, it's very sharp when stopped down (especially in the centre), shows minimal chromatic aberration, and has relatively low distortion; APS-C users will also benefit from extremely low vignetting. In most regards it comes very close indeed to its much more expensive bigger brother, the EF 50mm F1.4 USM, lagging marginally behind in corner sharpness at any specific aperture. The only real blight in imaging terms is the lens's bokeh, or rendition of out-of-focus backgrounds, which is anything but smooth with a distinct tendency to render bright highlights as obvious pentagons (it's a pity Canon didn't choose to use a diaphragm with 7 or 8 blades instead of 5).

Of course getting great optics for relatively little money means that corners have to be cut somewhere along the line, and in this case it's in the build quality. The 50mm F1.8 II may not be the most flimsily-constructed lens ever made, but I can't think of another currently on the market which can rival it for a sheer impression of plasticky-ness. Of course the flipside of this is that it's extremely light, and won't add much strain on your shoulder carrying it around all day, so it's a great option to throw in your bag for low-light shooting when travelling.

The other slight fly in the ointment is the autofocus; the micro-motor system is a little slow and therefore not an ideal choice for moving subjects. More problematically, focusing can be inconsistent and inaccurate in low light, something that will be most obvious when shooting at large apertures.

Given the price, it seems reasonable to assume that this lens will overwhelmingly be used on APS-C bodies, and in this context it's worth pointing out that it's sharper than any of the EF-S lenses we've tested so far (the 18-55mm F3.5-5.6 IS, 18-200mm F3.5-5.6 IS or even the 17-85mm F4-5.6 IS USM, which is at its best at 50mm). We suspect full-frame users will on the whole be buying more expensive optics, but to overlook this budget option completely would be a mistake, as it can demonstrably perform very well even on the 21Mp EOS-1Ds Mark III (and therefore also 5D Mark II) at its optimum apertures. That F1.8 maximum aperture lets in more than four times as much light as a typical kit zoom, and so allows shooting in low light while keeping shutter speeds relatively high; this therefore provides a useful alternative to IS when the aim is to keep moving subjects sharp. It also enables the user to experiment with selective focus techniques impossible with slow zooms.

So ultimately this is a lens which we'd encourage any Canon DSLR owner currently shooting with 'kit' zooms to try. The overall image quality when stopped down a bit is very impressive indeed, and the fast maximum aperture offers creative options which are well worth exploring (while sharpness, particularly in the corners, may not be the best wide open, the point is that you can get to F1.8 at all). It's a pity about the build quality and harsh bokeh, but ultimately this lens hits a price:performance ratio that's very difficult to beat.

Detail Rating (out of 10)

Build quality 5.5
Ergonomics & handling 7
Features 7.5
Image quality 8.0
Value 9.0

Κώδικας:

Πηγή : dpreview.com