What is a “White Paper”? Good question. Canon haven't released white papers for a while. They are highly informative documents that explain why a product has been built and how it compares to previously existing products.
Our in-house, Senior Technical Specialist from Canon, Phil Reid, helps us to unpack this dense treasure trove that explains everything you need to know about the new EOS R system.
Who makes a White Paper and where do they come from?
This White Paper came from Canon USA.
My understanding is that a white paper is a report of the development of a product. A White Paper can also be a guideline as to what a product is when it is released, usually distributed to sales divisions.
Canon hasn’t released a white paper for an EOS product for quite some time. I think the main reason for releasing it is to give people a really good, thorough background to the EOS R and range: what it is developed for, what the designers were thinking.
For the skim readers out there which parts jumped out for you?
I think the outstanding part is actually the lenses. The new shorter flange back allows lens designers to minimise distortion due to better angles for the light travelling through the lens to the actual sensor. You can see in the MTF graphs that the lens development in RF lenses is so much more advanced than what they’ve been able to achieve with the EF lenses.
How do you explain MTF graphs to people who haven’t looked at them before?
The actual name for it is Modulation Transfer Function, but the graph when referring to a lens actually measures the contrast and resolution from the centre of the lens to the corners of the lens.
I am a big believer in MTFs as they show you resolution performance and my base guideline for any new product is the MTF graphs. The MTFs compare previous EF versions to the new RF versions just released. And comparing the graphs for them last models or equivalent models, you can see that the RF 28-70 f2/L USM is an f2 lens but it is outperforming the current EF 24-70 2.8 MII at nearly all focal lengths.
Gradual natural fall off across a lens is normal. But with the new RF lens set and system design, they have been able to improve this phenomena.
This goes a long way to answering the question I think a lot of people have which is: why develop a whole range of new lenses for this system?
In lens design and body design, the shorter the flange to focal plane distance - that is the mount surface to the CMOS - the better you can design lenses to suit. But if you go too far there is also added distortion introduced as well. Canon has come up with a 20mm flange back distance for this camera, focusing on how they can get the best out of lenses. And it’s all about a compromise. You still need mechanics to fit: a blade shutter, contacts for communication and all the electronics. With a Canon DSLR the distance is 44mm.
When you are out on the field shooting with a camera with a shorter flange distance, what impact will this have on the way you work and what you can do?
Dramatic improvement in optical fall off is the biggest thing you’ll notice. You can also improve the centre performance of the lens just as much as the corners.
The biggest improvement is possibly the RF 28mm-70mm which is amazingly sharp at all focal lengths, from centre to corner. And you can only achieve that by changing the flange focal plane distance. The second biggest improvement I think is in the 50mm lens. So the current EF 50mm 1.2 L was originally released in 2005 and it was advanced at that point because no one else was doing a 50mm 1.2 autofocus lens. The optimal performance was slightly compromised at the maximum aperture - it has some softness. The development of the new 50mm lens means they’ve been able to greatly improve the performance at 50mm in both the centre and the fall-off. Dramatically. I would say just based on the MTF alone it is the best 50mm lens out there.
So I think this is the area that people need to focus on. The lenses are actually outstanding. The 35mm MACRO, though it is not an L series lens, performs incredibly well even against other flagship lenses. It has some natural fall off. But when you look at it against one of the best lenses we’ve ever produced, the 35mm 1.4MII, it’s not that far behind. And this is one of the sharpest lenses Canon has ever produced! This will be noticed by aerial shooters who need an image to be very sharp from corner to corner. And the f1.8 is a faster aperture sharp the whole way through.
I know some people are a bit skeptical about filters, saying why have all this beautiful expensive glass if you are putting a filter with inferior glass out in front of it? Does it make a difference if you place filters behind a lens?
Having this drop-in circle polariser and drop-in ND enable you to put in the filters behind these wide angle lenses. This has a few advantages. Normally you’d have to buy very expensive large diameter filters to enable them to be used. But now you have a more reasonable option. You are not producing as much glass and you are just dropping them in behind.
Optically there could be subtle advantages. When making filters you can have imperfections in glass. Over a large filter you may have minor imperfections but if you minimise the the size you minimise those imperfections. But the big advantage to having the filter at the rear of the lens is the direction of optical light. When light is travelling, it’s travelling more directly at the back end of the lens than it is at the front end of the lens. When you put a filter in front you are compromising the way the light travels through the lens. But at the back the light is already in a corrected path and the flare reduction of the lens is better used. The filter at the back makes perfect sense for outdoors with sun glare. You get much less. Also, a lot of people don’t realise that you have filter holders that might have light gaps in between the filters and the front element of the lens as well. So if you get light going in behind the filter and bouncing to the front of the lens it can cause bad flare. You can eliminate that by putting the filter behind.
Any final thoughts on the white paper?
It’s very thorough and it’s good for everyone to read because it is something you don’t often get to see. It is very good for someone who is focusing down to the detail investigating the right lens for their specific type of photography as it is important to understand the background of why lenses are developed and how. And some of the information included here is hardly ever seen in the market place - so it makes for an interesting read.