OpticalLimits Reviews the Canon RF 35mm f/1.8 IS Macro STM

Travel_Photographer

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Aug 30, 2019
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Disabling the Continuous AF in camera menu page 7 makes things much better. I'll spend some time shooting this way to verify. I might just keep this lens. I need it.

Excellent, and thanks for the update. I think you'll find it significantly better. I'm so glad you casually mentioned the part about it making the noise when you set it on a table... as soon as I heard that I figured you had Continuous AF on. Keep in mind too that it was doing that with all your lenses. You just may have never noticed because the focus on your 70-200 or any other lenses you have is much faster. It would have been constantly hunting and focusing with every single lens, all the time. I imagine it totally drains your battery as well.
 
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Since when did a 1:2 become a true macro lens. My understanding is that macro lenses are 1:1 on a full frame sensor or greater. I've seen 5:1 but never 1:2 considered macro. Sounds like a marketing ploy using cheaper materials than the L line

since around the birth of EOS.. the 50mm F2.5 Compact Macro is .5x but could go to 1:1 with the lifesize converter.
 
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Sep 26, 2018
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Since when did a 1:2 become a true macro lens. My understanding is that macro lenses are 1:1 on a full frame sensor or greater. I've seen 5:1 but never 1:2 considered macro. Sounds like a marketing ploy using cheaper materials than the L line

The "official" definition of macro is that the image on the sensor is life-sized (1:1). I've never heard qualifications about the sensor size though.

It's always seemed arbitrary to me though, whether you really need 1:1 depends entirely on what you're photographing. A small close focusing distance is always useful whether you're doing "macro" work or not
 
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brad-man

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Since when did a 1:2 become a true macro lens. My understanding is that macro lenses are 1:1 on a full frame sensor or greater. I've seen 5:1 but never 1:2 considered macro. Sounds like a marketing ploy using cheaper materials than the L line
You do understand that it's not an L lens, right?
 
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Optics Patent

Former Nikon (Changes to R5 upon delivery)
Nov 6, 2019
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Since when did a 1:2 become a true macro lens. My understanding is that macro lenses are 1:1 on a full frame sensor or greater. I've seen 5:1 but never 1:2 considered macro. Sounds like a marketing ploy using cheaper materials than the L line

since when is a 35mm lens a “macro”? What genius thinks they can light a subject two inches from the lens?

If they are accurately describing the specs then the huffing is unjustified
 
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The huge deal here is FOCUS SHIFT, rendering this lens total garbage.

For those who don't know, your AF selects accurate focus @ f1.8, then as you take the photo the lens stops down to your selected aputure (say f2.8) and the focus point changes due to the aputure change... It's not till you get enough DoF (ie f4.0) to cover the shift that everything is 'all right' again.

The only way to avoid it is to use live view, so your aputure doesn't change after focus.
 
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SecureGSM

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Feb 26, 2017
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The huge deal here is FOCUS SHIFT, rendering this lens total garbage.

For those who don't know, your AF selects accurate focus @ f1.8, then as you take the photo the lens stops down to your selected aputure (say f2.8) and the focus point changes due to the aputure change... It's not till you get enough DoF (ie f4.0) to cover the shift that everything is 'all right' again.

The only way to avoid it is to use live view, so your aputure doesn't change after focus.
In live view mode camera still focusing at the widest available aperture. This is my understanding happy to be corrected.
 
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Since when did a 1:2 become a true macro lens. My understanding is that macro lenses are 1:1 on a full frame sensor or greater. I've seen 5:1 but never 1:2 considered macro. Sounds like a marketing ploy using cheaper materials than the L line

Canon calls the new TS-E lenses (50mm, 90mm, 135mm) macro though their max magnification is 1:2. IIRC, I've read that back in the film days, lenses with max magnification of 1:4 were also called macro, though I can't find the source at the moment.
 
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koenkooi

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Feb 25, 2015
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since when is a 35mm lens a “macro”? What genius thinks they can light a subject two inches from the lens?

If they are accurately describing the specs then the huffing is unjustified

The Canon MTxx flashes can, as well as their 35mm lens with builtin lighting: https://www.the-digital-picture.com/Reviews/Canon-EF-S-35mm-f-2.8-Macro-IS-STM-Lens.aspx

Or use a hot-shoe cord and put your flash on a flexible arm or something. The Canon MP-E and Laowa lenses have a working distance of less than 2 inches at maximum magnification.
 
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Optics Patent

Former Nikon (Changes to R5 upon delivery)
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A small close focusing distance is always useful whether you're doing "macro" work or not

Potentially useful but in this case at a cost of 3/4 of the focusing range being less than a foot so it can spend most of its effort where the subject isn’t. Which is why some lenses have focus range limit switches. Usually (such as with telephotos having limit switches) closer is better. For AF macros without a switch when macro shooting is not the goal, there’s a potential downside.

As far as the concern that reducing the aperture to remove some peripheral rays can defocus the central rays as has been recently explained with appreciated clarity, I’ll have to test that at normal focal distances.
 
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Optics Patent

Former Nikon (Changes to R5 upon delivery)
Nov 6, 2019
310
248
The huge deal here is FOCUS SHIFT, rendering this lens total garbage.

For those who don't know, your AF selects accurate focus @ f1.8, then as you take the photo the lens stops down to your selected aputure (say f2.8) and the focus point changes due to the aputure change... It's not till you get enough DoF (ie f4.0) to cover the shift that everything is 'all right' again.

The only way to avoid it is to use live view, so your aputure doesn't change after focus.

Very clear explanation. I sought to replicate this with a flat subject at 30" from the lens. f1.8, 2, 2.8, 4, 5.6, 8. All indistinguishable at full magnification of the finder. Is this something rarely encountered like the RF70-200 near close focus error? I'd like to understand this better before I dismiss the concern as irrelevant to my usage (like the to-be-fixed RF70-200 focus error).

With a foreshortened ruler I thought I might have seen some shift, but had a hard time replicating (if it isn't repeatable, it isn't science).

I'd be happy to see a link to anyone who has published tests I can replicate.
 
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Travel_Photographer

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Aug 30, 2019
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Very clear explanation. I sought to replicate this with a flat subject at 30" from the lens. f1.8, 2, 2.8, 4, 5.6, 8. All indistinguishable at full magnification of the finder. Is this something rarely encountered like the RF70-200 near close focus error? I'd like to understand this better before I dismiss the concern as irrelevant to my usage (like the to-be-fixed RF70-200 focus error).

With a foreshortened ruler I thought I might have seen some shift, but had a hard time replicating (if it isn't repeatable, it isn't science).

I'd be happy to see a link to anyone who has published tests I can replicate.

It's a non-existent problem. The lens focuses flawlessly in both autofocus and manual modes. Some reviewers just like to come up with something to discuss. It's a natural optical phenomenon with wide aperture lenses that generally causes no-real world effects, as you have seen in your own tests. Feel free to enjoy your lens worry-free about AF issues. If it actually had this problem, it wouldn't be rated so highly almost universally. Perhaps most importantly, the ultimate test of a lens's performance is how well it works for you. If it works great for you and gives you the results you want, that's all that matters.
 
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Optics Patent

Former Nikon (Changes to R5 upon delivery)
Nov 6, 2019
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It's a non-existent problem. The lens focuses flawlessly in both autofocus and manual modes. Some reviewers just like to come up with something to discuss. It's a natural optical phenomenon with wide aperture lenses that generally causes no-real world effects, as you have seen in your own tests. Feel free to enjoy your lens worry-free about AF issues. If it actually had this problem, it wouldn't be rated so highly almost universally. Perhaps most importantly, the ultimate test of a lens's performance is how well it works for you. If it works great for you and gives you the results you want, that's all that matters.
I’ve just shot a real world test of sunlit toddler with eye focus and all apertures are eyelash sharp. If it can do that I don’t care much about some bloggers lab results.
That said, this optics industry technology expert is interested in the principles by which removing outer rays can shift a sharp central focus point. I have an open mind.
 
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Travel_Photographer

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Aug 30, 2019
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If it can do that I don’t care much about some bloggers lab results.

Exactly. It's some bloggers lab results.

As for the physics of it, see the diagram below. In the top example, with the aperture wide open (which it would be during autofocus) the light rays enter from a variety of more extreme angles, creating a focus plane that is not a single point, but rather a bit of a blurry blob. The AF would focus in the middle of this blurry blob (the middle vertical green line).

In the second example with the aperture stopped down slightly, the "extreme angle" rays entering the lens are eliminated by the smaller aperture opening, producing a more accurate point of focus, in this case, shifted slightly leftward (the vertical red line).

These are all tiny amounts (if at all) measured in some lab, as you correctly state. Aspherical elements in the lens can eliminate or drastically reduce it.

Your real-world tests with this lens are the same as mine -- excellent autofocus at all apertures and distances.

Focus.jpg
 
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Optics Patent

Former Nikon (Changes to R5 upon delivery)
Nov 6, 2019
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Excellent, thanks. This fits with my reading that the actual point of focus gets sharper at smaller apertures and NEVER gets worse by stopping down. It is a “one hand clapping” philosophical matter of whether at a reduced aperture there is a focus setting that provides slightly sharper focus?

My lens is sharp wide open and get sharper at every reduced aperture until diffraction intervenes. I’m a little sorry I wasted time on this. But glad to have learned a bit more. Clients come to me and are glad I’ve already been familiarized with their issues like these.

a
 
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Note that on RF lenses the focus ring is complete controlled by software, there are a few options in the camera to tweak it, one of which is the direction. Maybe it has a section for sensitivity as well?
DPReview TV did an item a few weeks back about software controlled focus limiting, a thing I would very much like to have.
But I want it for the reverse: lock it down from MFD to 1 meter so it stays in macro mode. It's very annoying when you try to focus on an insect and it grabs the background instead.
I too would like a menu option to limit focus range. My 100mm f/2.8 macro has the switch which is great when I am shooting above water but not accessible when in an underwater housing :)
Mostly I would shoot close up/macro subjects under water with the lens but occasionally further distant subjects if the vis is okay. Only option now is to keep the full range available and put my hand in front to bring the focus close and start the focusing close up. The focus hunting can be quite annoying though.
 
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Jan 16, 2019
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Here's my verdict on the lens: It is one of the best values among all 35mm lenses. With EOS R, it can AF in almost complete darkness, is very sharp even at f1.8 (at least at distances where it matters), it has IS, it focuses fast, it has 1:2 magnification, it is fairly light and small for such a lens and it is dirt cheap when bought with a body (I bought in Norway). I didn't notice that bad vignetting and CA is OK (not bad, not the best). I had EF 35mm f2.0 IS USM as well and this lens is better than that already great lens.
 
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jd7

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Feb 3, 2013
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Here's my verdict on the lens: It is one of the best values among all 35mm lenses. With EOS R, it can AF in almost complete darkness, is very sharp even at f1.8 (at least at distances where it matters), it has IS, it focuses fast, it has 1:2 magnification, it is fairly light and small for such a lens and it is dirt cheap when bought with a body (I bought in Norway). I didn't notice that bad vignetting and CA is OK (not bad, not the best). I had EF 35mm f2.0 IS USM as well and this lens is better than that already great lens.
Out of curiosity, what do you like better about the RF 35 over the EF 35/2 IS?

From what I’ve seen and read, I had the impression the RF 35 may be a touch sharper, and of course it has its macro ability, but the EF has better bokeh (probably not noticeable at close focus distances but noticeable one the subject is a bit further away), faster AF and perhaps slightly less CA. I’ve never shot the the RF myself though, and I haven’t owned the EF for years, so I haven’t tested them head to head myself.
 
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