Canon EOS 70D: Performance

by Jim Keenan Reads (1,401)
Editor's Rating
9.00

TG Ratings Breakdown

    • Image/Video Quality
    • 10
    • Features
    • 8
    • Design / Ease of Use
    • 9
    • Performance
    • 9
    • Expandability
    • 9
    • Total Score:
    • 9.00
    • Rating 1 to 10, top score 10

Performance

The 70D starts promptly (Canon specs say .15 seconds), but like the 60D has a default setting of sensor cleaning at both start up and shut down. Sensor cleaning can be immediately aborted by a half press of the shutter button and sensor cleaning altogether can be disabled. There is also an internal menu setting that permits manual sensor cleaning. Single shot-to-shot times are typical mid-range/high end DSLR: a function of how quickly you can reacquire focus and press the shutter button again after each shot. With a high-speed continuous shooting rate of up to 7 frames per second the 70D has the potential to rack up a lot of frames in a hurry if you hold the shutter down for any extended period of time. Fortunately, Canon has provided a fairly decent buffer capacity to match the motor performance, at least if you stick to RAW or JPEG Fine images: utilizing a Lexar 32GB 600x SDHC card produced 18 shots in RAW format and 64 shots and JPEG Fine before the shooting rate slowed. Shoot RAW/JPEG Fine combinations and the 70D slows up after only 8 images.

Write times for the complete bursts are impossible to calculate as the camera allows you to resume shooting as soon as there is buffer space available – the “busy” designation that appears in the viewfinder goes away as soon as space becomes available. But even after a full burst of RAW or JPEG Fine images, the camera could resume shooting at full speed in a few seconds, albeit for only 2 or 3 images.

Much of the advertising buzz surrounding the 70D has to do with the new autofocus system — “Dual Pixel CMOS AF employs a revolutionary CMOS sensor on which all of the effective pixels are able to perform both still imaging and phase-detection AF simultaneously to achieve dramatically improved AF performance over other EOS cameras during Live View shooting and when shooting video”. We’ll discuss video AF performance later but first a few observations about AF performance with still images.

The 70D AF system does seem to offer improved AF performance during live view shooting of still images, principally in shorter focus acquisition times in good light than have been available in past cameras. AF acquisition with live view for still images is quicker in good light than it was in the 60D, but not as quick as times obtained using the viewfinder. In dim light the 70D system has not impressed me as being a measurable improvement over the older camera – our review unit struggled in dim light with live view and often could not acquire focus on a scene in which switching to the viewfinder produced a quick acquisition of focus. If I was shooting the 70D for still images I would shoot live view only if the viewfinder was absolutely, positively unavailable for the shot I wanted to make.

Still image AF using the viewfinder with the new system is capable and fairly quick – possibly a bit quicker than the 60D – but overall I’m not sure I noticed that much difference between the two cameras (with the caveat being that I shot the 60D back during its introduction over 3 years ago). Adding 10 more focus points to the mix doesn’t seem to have demonstrably upped still image autofocus performance over the older camera.

The built-in flash guide number of the 70D is a bit lower than the 60D, approximately 39.4 feet at 100 ISO versus 43 feet in the older camera. Given the f/4-f/5.6 maximum aperture range of the 55-250mm that translates to a maximum flash range of about 9.85 feet at wide-angle and about 7 feet at telephoto. Flash recycle times on the 70D were fairly quick with a fully charged battery — full discharges recycled in about 2 seconds while partial discharges took even less time. With the flash enabled the 70D will not allow you to take another photo while the flash is recycling.

Battery life is listed as 1300 images using available light; this figure drops to 920 images with 50% flash usage. Live view shooting figures are 230 and 210 images under the same conditions. There is an optional Battery Grip BG-E14 that utilizes a second battery, doubling the above listed battery life.

Lens Performance
The EF-S 55-250mm f/4-5.6 IS STM zoom lens provided with our 70D is a new addition to the Canon lineup and is notable for the inclusion of the quieter STM stepping motor; Canon also makes a stabilized 55-250 without the stepping motor. This lens is currently available at reputable Internet vendors for about $349; the non-STM version is about $50 cheaper.

The lens features a composite barrel and lens mount and Canon reports its stabilization system can provide up to 3.5 stops of shake correction. The lens appears well-built; point of manufacture is Malaysia. The zoom ring requires — turn to go from one focal length extreme to the other and I found this action to be smooth and consistent. The front element of the lens does not rotate during either zooming or focus changes.

Maximum aperture at the 55mm wide-angle end of the lens produced an image with a bit of softness in the corners and edges, but not an overly dramatic change from the center of the frame, which was fairly sharp. Closing down two stops to f\8 produced improved sharpness over the entire frame. At the 250mm end maximum aperture produced noticeably soft corners and edges, but at f/8 edges had improved to closer to center frame sharpness while the corners had lost most of their softness. Vignetting (darkening in the edges and especially corners) was noticeable at maximum aperture at both focal extremes.

There was longitudinal chromatic aberration (purple fringing) present at both ends of the lens with the effect being more pronounced at the telephoto end. In both cases the defect was relatively benign and required enlargements in the 300 to 400% range to be readily visible. The 70D features a two-stage lens aberration correction setting that is enabled by default and helps correct for chromatic aberration along with peripheral illumination (vignetting). I shot the camera with this feature both enabled and disabled and found no change in shooting times due to processing with it enabled; the improvement in image defects was apparent, particularly pixel-peeping with regards to chromatic aberration.

Video Quality
While I found the new autofocus system to be capable, if unspectacular, with regard to still image capture the same cannot be said for AF performance during video capture. The 70D is by far the best autofocusing DSLR in video capture that I have ever had my hands on. Not just in the Canon family (where the 60D didn’t even offer continuous video AF) but Sony, Olympus, Pentax and Nikon. While it turned in a stunning continuous AF performance in good light, the 70D struggled to acquire focus in dim light to the same degree as the camera did with still images – and in both cases we’re talking about dim light but some fairly contrasting details that the camera acquired promptly in still image capture using the viewfinder.

Canon has been producing nice image quality with videos out of their DSLRs for some time now, and the 70D is no exception, but to me the strong point of this camera is clearly the autofocus system and performance with regard to video capture. One of the tests I threw at the AF system was to acquire focus and initiate video capture on some plants at my feet, about 5 feet away. I then swung the camera immediately to capture rosebushes and a mailbox about 25 feet away; this was followed by a rapid pan to a neighbor’s house across the street perhaps 100 feet away and another rapid pan to a palm tree about 100 yards away. Finally, I panned directly from the palm tree back to the plants. Focus was established promptly on all these separate points with no hunting whatsoever, and in fact it seemed that focus had been established by the time the camera stopped panning in each instance. Here’s a look at this test clip–decide for yourself just how well the 70D performed.

Another aspect of video recording that I like in the 70D versus 60D is the movie capture process has been removed from the mode dial. It’s a more simple matter to simply flip the live view/movie shooting switch with the thumb of the right hand, establish focus with the shutter button and then initiate capture with the thumb. So, a more seamless video capture interface than the earlier camera along with a simply amazing AF system makes for a very potent video capability.

The 70D utilizes a CMOS sensor so rolling shutter effect can be a concern, but I found the effect well controlled with the exception of exaggeratedly fast pans. The built-in stereo microphone can be supplanted by an external microphone, and is susceptible to wind noise. Audio may be captured automatically or by manual control and there is a wind cut feature available. There is an in-camera video editing suite available and, as always, the camera may shut down before video capture limits are reached in order to prevent damage due to overheating.

Image Quality
Default still image quality of the 70D was quite nice, with accurate color rendition and fairly pleasing sharpness.

Even so, I maximized sharpening in each picture style within the camera. “Auto” is the default picture style but there are also standard, portrait, landscape, neutral, faithful, and monochrome options available. Visually, there’s not a lot to separate the various picture styles with standard, neutral, faithful, and auto offering very accurate color renditions while landscape saturates colors a bit more deeply. Disneyland images used in this review were shot in the “disable flash” auto mode where the camera handles all settings; other shots were generally aperture priority in the standard picture style. Here’s a look at the auto, standard, landscape, neutral, faithful and monochrome offerings.

AUTO                                                                                            STANDARD

LANDSCAPE                                                                                           NEUTRAL

FAITHFUL                                                                                          MONO

A 3:2 aspect ratio is the default setting for still images, but 4:3, 16:9 or 1:1 ratios may be enabled by the user. Maximum resolution (file size) in both RAW and JPEG images is achieved in 3:2. Images are output at 72 dpi regardless of aspect ratio – great for email transmission but needing resizing for printing.

Evaluative metering is the default setting for exposure calculation and recommended for most shooting scenarios – creative zone shooting modes offer partial (center, approximately 7.7% of viewfinder), spot (center, approximately 3.0% of viewfinder) or center-weighted average metering options. I found the 70D when shot utilizing evaluative metering seems to be biased a bit more toward shadow detail than the 60D – the 70D seems to fairly consistently lose highlights, particularly in high contrast situations (which are a difficult exposure test for most cameras). But I was somewhat surprised that the 70D also seemed to overcook highlights in a lot of scenes where the light distribution looked a lot more average. If I were shooting a 70D as my personal camera I’d probably introduce a bit of exposure compensation for JPEG images or shoot RAW files and fix any blown highlights in post processing.

Auto white balance was used for all the images captured by the 70D in this review and worked well across a variety of light types, including daylight, cloudy, open shade and flash. Like the 60D, the 70D shot a little bit warm on auto white balance under incandescent (3200K) light. In addition to auto there are presets for daylight, shade, cloudy, tungsten light, white fluorescent light and flash, as well as a user-defined custom setting and a Kelvin temperature setting.  Not surprisingly, the 70D was spot on with white balance when shot at either the tungsten or Kelvin option when set to 3200 degrees – it turns out the tungsten preset is based on a 3200K light source.

ISO noise performance in the 70D reminded me strongly of the 60D, which is to say quite good. Because my personal preference is to leave high ISO or long exposure noise reduction to post processing, the initial batch of ISO samples were shot with all noise reduction disabled in the camera. 100 and 200 ISO are virtually indistinguishable and the bulk of my creative zone shooting for this review was shot at 200 ISO in order to pick up an extra bit of shutter speed. 400 shows a bit of grain beginning to appear and there?s a bit more at 800 but ISO settings from 100 through 800 are basically interchangeable for large print work. 1600 picks up a proportionately larger increase in grain but is still quite clean and might possibly be useful for large prints as well; 3200 shows a marked increase in grain and the beginnings of some chroma (color) noise and I would probably leave it for smaller prints unless there was no other way to get the shot. 6400 looks like the tipping point for this sensor, with grain, chroma noise and artifacts ramping up noticeably. 12800 shows a modest increase in grain, chroma noise and artifacts and 25600 displays another large deterioration as colors begin to fade in addition to noticeable jumps in grain, chroma noise and artifacts. 6400 might be usable for small prints and Internet traffic but 12800 and 25600 are best left as sensitivities of last resort if you don’t plan to employ noise reduction.

ISO100                                                                               ISO200

ISO400                                                                               ISO800

ISO1600                                                                          ISO3200

ISO6400                                                                         ISO12800

ISO25600

However, remember that the above samples don’t include noise reduction – for comparison purposes here are 3200, 6400, 12800 and 25600 ISO images with the 70D default high ISO noise reduction setting (“standard”) enabled. There are also “low” and “high” NR in-camera settings that may be user specified.

ISO3200 NR ON                                                           ISO6400 NR ON

ISO12800 NR ON                                                         ISO25600 NR ON

Clearly, noise reduction offers some significant gains in the higher ISO settings, whether you choose to have the camera do it or save it for post processing. Canon advises that when shooting at 12800 or above in the continuous high-speed setting with noise reduction enabled that the 7 fps shooting rate will be greatly slowed due to in-camera NR processing. 

Additional Sample Images


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