CANON LEGRIA HF G70 CAMCORDER Review 2. Noise? What Noise? The swings and roundabout of sensor sizes and lens apertures

It is a truism that a large sensor will show less obvious noise in low light than a small sensor. Given equal processing and noise reduction algorithms, a camera with a large sensor and not too densely packed pixels must perform better in low light than a camera with a tiny sensor. That sounds obvious but in practice there is another factor at play in video recording: the lens aperture. Since the exposure for video is constant or virtually so (i.e. 1/50th of a second for 25 frames per second or 1/60th for 30 fps) the aperture of the lens is the determinant of how much light reaches the sensor over that period. More light equals a higher signal:noise ratio and, therefore, less noise. Some people, many online, interpret having to increase the ISO setting, or gain, as the cause of the noise. That is not so. Increasing the ISO setting simple increases the gain of the amplifier to make the image visible; both signal and noise are increased.

The Canon HF G70 has a 1/2.3”* sensor. The maximum aperture varies across the zoom range between f/1.8 and f/2.8. To see how good—or bad—the noise was in low light I compared it first with the main camera on the iPhone 14 Pro (‘main’  f/1.78, said to be size 1/ 1.28"). This test was done in a dim, northerly facing room in daylight. The Exposure Value was 4. In the deepest shadow area there was a little noise and I could not find any difference between the Canon HF G70 and the iPhone. I then compared the HF G70 with my Nikon Z7, which because of the very large number of pixels is known to be noisier than the Z6. I put on a 50mm f/1.8 lens. The Exposure Value was 4.3. Again there was a little noise at f/1.8 (ISO was 800), slightly less perhaps than on the HF G70 and iPhone. However, when I turned the aperture to f/4 (keeping the shutter speed at 1/50 and letting the ISO setting increase to 4000), there was marked noise. In other words, my Nikon Z7 in full-frame mode at f/4 was noisier than the Canon HF G70 and the iPhone 14 Pro at f/1.8. The difference between f/1.8 and f/4 is 1⅓ stops (EVs) but of course a more than doubling of the light hitting the sensor.

In other words we are talking about trade-offs with apertures, sensor size and depth-of-field. One advantage of using a full-frame camera is being able to isolate a subject in a narrow depth-of-field. However, with video, the depth-of-field at f/1.8 is wafer thin. With a 50 mm lens at a distance of 5 metres it is only around 20 cm. Therefore, it is highly likely that I would want to use a smaller aperture. With a smaller sensor, the same depth-of-field can be attained at a larger aperture so what you gain on the swings by using a camera with a larger sensor, in terms of noise, can easily be lost on the roundabouts of using a smaller aperture.

This is all a very long-winded way of saying that I am very pleased with the performance of the Canon HF G70 in low light. My guess is that Canon have got it as good as it can be with the current state of technology. All my trials have been with 4k video. I note that Canon in their marketing of this camera stress ‘Over Sampling HD Processing High quality Full HD. Uses the 4K UHD sensor to deliver superior Full HD images’. I haven’t tested that yet.

While I was doing all this I realised something I had not fully taken in before. When my Sony AX-53 (also a 1/2.3” sensor) broke down in use (cash refunded by Amazon) and I unwisely bought the Sony AX-700 just before covid lockdown (camera also broke down in use and just out of extended warranty but with very few minutes on the clock) that the advantages of the larger (the so-called 1” sensor) in terms of noise and of a slight isolation of any subject at larger apertures, were offset at least partially, by the smaller maximum aperture of the lens. The AX-53 is f/2-f/3.8 over its zoom range; the AX-700 f/2.8-f/4.5. The Canon HF G70 as I noted earlier is f/1.8 and f/2.8 (over a much wider zoom range).

Unfortunately, it is not worth trying to show the videos of the trials; the definition here and on YouTube is just not good enough for any difference to be illustrated. It is also worth pointing out that while I always try to take 4K, I normally put this on a 1080 timeline thus giving me the opportunity to zoom in by cropping without losing definition. I did that with all the samples (where I could spot the noise on playback on my 24” Mac with 4K Retina Display). However, when I did as I usually do, output the video as an MP4 file and looked at it on a television (no, not one of those huge things that fill a wall) I could see no noise, except for the slightest flicker evident in the footage from the Z7 at f/4.

*Desperately needed is some international standard for sensor sizes in cameras. The use of fractions of inches and the like can be utterly confusing. We need  the dimensions in mm--a simple statement some manufacturers are very reluctant to state. That, together with the number of pixels should be a standard imposed. 

Coming Next: Ergonomics and Setup

CANON LEGRIA HF G70 CAMCORDER Review 1.’ IR Mode’ Confusion

To replace the died-in-service Sony AX-700 which in turn replaced the died-in-service Sony AX53, I considered all sorts of options, from using my or another full-frame or aps-c mirrorless camera, to relying on my bridge camera, or, in a decreasing market, to get another camcorder. I should explain at the outset that I want a video camera for my specific purpose not, as most people write about, for commercial advertising or for making wedding videos for customers. Opinions from the latter seem to dominate online.

Having tried all sorts of cameras and having retried them after the Sony died, I still find a camcorder the best for wildlife. The weight and form factor are important. The grip is ideal for holding the camera steady and the microphone does not have to dangle from a perch on top. It can also be ready to use in seconds. If I were just taking personal travel videos I would simply use my latest-generation iPhone with its state-of-the art computational photography. But for wildlife, a long-focal length lens is needed, and some camcorders fill that bill.

There are very few camcorders now being made that fit into the ‘prosumer’ category. Sony had no new models and I did not want to pour any more money down that particular drain. I have used Panasonic camcorders in the past but have always been disappointed with the autofocus, limited to contrast detection and often found to focus on something that could be focused on rather than something which needed to be focused on. In that respect, the Sony, with its on-sensor phase and contrast detection, was superb.

Then I found that last September Canon had released a new range of camcorders. Amongst them was the HF G70, called a Legria model in PAL countries and Vixia elsewhere. But I could not find a single review of the model anywhere; nothing, apart from Canon’s own marketing material (website here).

Canon HF G70 (from Canon Website)

Reading the specifications I was in two minds. The Sony AX-700 hit that sweet spot of sensor size. The so-called 1-inch sensor produced relatively low noise in low light compared with the smaller, 1/2.3 inch and now, I see, 1/2.5 inch, of most camcorders aimed at the low-end and prosumer markets. Notwithstanding some excellent features, the HF G70 seemed a backwards step to a 1/2.3 inch sensor. However, it is a brand-new model compared with the Sony models still on the market six and more years since their introduction. There has been time for improvement in sensors and electronic processing of the signals over those years, so I decided to go with the Canon. Very few UK retailers had it in stock which I presume is still down to the shortage of chips. However, WEX did and were offering a free extra: a large additional Canon battery. WEX soon had it on my doorstop.

In this series reviews as I set up and use the camcorder, I will concentrate only on those aspects important for my purposes. But before that, in this first article, I should point out a puzzling mismatch between the marketing material, clearly derived from Canon, being used by some dealers, the instruction manual and the capabilities of the camera. That mismatch extends to within the list of specifications on the Canon website. The question is simple: what’s all this about an infrared or IR mode?

In the overview section on the Canon website:

A host of outputs and recording options include Infrared mode…

The overview of the camcorder’s features on the websites of a number of dealers throughout the world shows a bueelt point:

Infrared mode captures high-quality video in low light

Then the ‘Specifications’ section of the website contradicts itself. Here in the Exposure section we have mention of an |R mode:

Exposure Metering

Center-weighted average metering 

AUTO, P, Av, Tv, Portrait, Sports, Low Light and IR modes 

Segment evaluative metering 

Night Scene, Snow, Beach, Sunset, Spotlight modes 

No metering in Fireworks mode: Exposure constant

But then under Shooting Modes we see: 

Infrared Shooting Mode     Not supported

There is no mention in the instruction manual of an IR mode or of infrared. I have also searched the camera menus and controls for anything about an IR mode. I have tried the low light and night modes to see if there is any sign of infrared or near infrared detection being used in the imaging process even though the IR Mode is mentioned as something distinct. Again, no.

When I read the marketing blurb I assumed that there was an infrared mode, akin to Sony’s night mode which produces a green hued monochrome image in response to an infrared source or infrared illumination from the front of the camera. There clearly isn’t but what has been going on with the introduction and marketing of this camcorder? Was an IR mode planned for this camera but then ditched before release? Indeed an IR Mode is present in the 'professional range. Did those responsible for marketing not get the message or only half one? Whatever happened, Canon need to clarify what is and is not in the list of features of the HF G70. Otherwise those thinking they were going to get an IR video in the dark functionality will be disappointed.