Would a higher resolution EOS R combined with an RF 50mm f1.2 render the RF 85mm f1.2 redundant/irrelevant?

Kit Lens Jockey

EOS 7D MK II
Nov 12, 2016
500
174
I finally broke down and bought a good deal on an open box RF 50mm f1.2 lens for my EOS R. Very happy with the lens. I also have an EF 85mm f1.2 II which is a little less than amazing wide open, at least by modern standards. So I'm eyeing up the RF 85mm f1.2. But the talk of a higher resolution EOS R coming soon has got me thinking... Would the RF 50mm f1.2 combined with a higher resolution EOS R model be nearly as good as having the RF 85mm f1.2?

The way I look at it, the RF 50mm has proven to be a very sharp lens. On a higher resolution camera, cropping down to be equivalent to an 85mm focal length seems like it would leave me with just about the same image as if I would have taken it with the 85. Maybe slightly less sharp, but I'm not sure it would be worth the $2600 and changing lenses, as good as the 50mm seems to be.

(Also, for people about to go on about focal length compression, I don't think a cropped 50mm image would be any different than a full frame 85mm image, according to this. https://photographylife.com/what-is-lens-compression . However I'm not sure about the DOF effects of 50mm and crop compared to 85mm uncropped.)
 

Viggo

EOS 5D SR
Dec 13, 2010
4,094
649
They are quite different and for headshots I couldn’t use only the 50. I tried (close’ish) portraits with the 50 and compared it to the 85, and it looks way to wide angle for my taste. And to just crop away, meh, not for me at least.
 

neuroanatomist

I post too Much on Here!!
Jul 21, 2010
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You could crop to the same foreground composition, but the perspective is going to be different. Not saying this is bad or that you wouldn't like it, but just different.
The perspective doesn’t need to be different, since perspective is a function only of distance to subject (i.e. focal length has nothing to do with perspective).

@Kit Lens Jockey, as long as you frame more loosely with the 50 then crop to the tighter framing the 85 would have given, and as long as you don’t want/need the extra MP, you’d be fine with a (potential future) high-res EOS R and the RF 50/1.2L.
 
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koenkooi

EOS 7D MK II
Feb 25, 2015
425
253
In my week long side-by-side test, the RF85 was slightly better in every aspect: it's sharper, has faster AF, less CA, etc. But the main problem I had with the RF85 is that I bumped into way too many walls/doors/fences when I tried to get the framing I wanted. So while I liked the RF85 best, the RF50 would fit my house and garden better :)
Given your choice, I don't think it's $2600 better, but if it was $800 or so I personally would be very tempted to switch.
 

Dantana

EOS RP
Jan 29, 2013
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Los Angeles, CA
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The perspective doesn’t need to be different, since perspective is a function only of distance to subject (i.e. focal length has nothing to do with perspective).

@Kit Lens Jockey, as long as you frame more loosely with the 50 then crop to the tighter framing the 85 would have given, and as long as you don’t want/need the extra MP, you’d be fine with a (potential future) high-res EOS R and the RF 50/1.2L.
Maybe I'm using the wrong term, so I apologize. Perhaps it's not "perspective'" though that's how it gets computed in my brain. The angle of view of the 85 is narrower than the 50. Cropping in on the 50 for a subject in the foreground will not result in the same background. It may not be noticeable, depending on how far back things are.

Again, not saying it's a bad choice. In fact, if I were to buy one of those two lenses, it would be the 50 because I know I would use it more.

Or maybe I'm just not thinking of this right.
 

Kit Lens Jockey

EOS 7D MK II
Nov 12, 2016
500
174
Did you look at the link in my first post? It talks a lot about focal length compression and how it really works. The conclusion is that shooting a subject a certain distance away from it with a wide lens and cropping down gives you pretty much the exact same look/perspective as if you had shot it from the same distance away with a longer lens and not cropped it.

The advantage of using a longer lens obviously though is you now have a photo that has the perspective you were after but is at the full resolution of your camera, compared to shooting wide and cropping, which obviously gives you a lower resolution. But if we're going to get a super high MP camera coming soon, and the 50mm is as good as it is, I'm wondering how much that will matter.
 
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neuroanatomist

I post too Much on Here!!
Jul 21, 2010
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Maybe I'm using the wrong term, so I apologize. Perhaps it's not "perspective'" though that's how it gets computed in my brain. The angle of view of the 85 is narrower than the 50. Cropping in on the 50 for a subject in the foreground will not result in the same background. It may not be noticeable, depending on how far back things are.

Or maybe I'm just not thinking of this right.
You're right that you're not thinking of this right. If you frame the subject the same with 50 and 85, you'll be closer with the 50 and the perspective will be different (i.e. the relationship between the foreground and the background will be different). If you shoot with the 50 and 85 at the same distance from the subject, then crop the image from the 50 to match the FoV of the 85, the perspective is the same and the relationship between the foreground and the background will be the same.

This is from a post of mine way back in 2012:

Here's an example from the wiki page on perspective distortion, an example that illustrates some of this confusion:



You see the different focal lengths printed on the images, and you see the relative sizes of the two water bottles changing, and you think that focal length is the reason. Even the text in the caption of that image suggests the effect is due to focal length. But consider...the pink bottle is the same height in all three images - therefore, as the focal length is reduced, the camera must have been moved closer to achieve the same framing. It's the movement of the camera, not the change in focal length, that results in the different perspectives.

Let me try to illustrate what I mean with a similar set of examples, but where I first vary just focal length but not distance, and then vary focal length and distance. Since I prefer beverages other than water, I selected a different pair of subjects for a similar test.

Perspective.jpg


The two bottles are 18" apart, and the distances in the image above are measured from the sensor to the front bottle. All were shot at f/5.6. As described above, it's normal for the bottle in front to look larger, that's perspective - objects that are further away look smaller, even though we know they are the same size. Note that the bottle in front is the same height in all the images.

In the left column, the 50mm and 24mm shots were at the same distance as the 100mm images, and the images were cropped to match the framing of the 100mm image. As you can see, the relative size of the rear bottle is the same in all the images. The perspective is the same - the two bottles maintain the same relative size, despite the differing focal lengths. The distance is the same, so the perspective is the same.

In the right column, which is equivalent to the water bottle shots from the wiki page, the 50mm and 24mm shots were taken at successively closer distances to the bottles, matching the framing to the 100mm shot by moving the camera. As you can see, the relative size of the rear bottle gets smaller as the camera is moved closer. Different perspective, because the distance is changing. Comparing the side-by-side 50mm and 24mm images, you can see that with the same focal length but different subject distances, the perspective is different.

So, varying focal length alone, without changing distance, does not affect perspective. As stated above (by me and others), perspective is determined by distance, and distance alone.

As others pointed out above, 'telephoto' compression and 'wide angle' expansion distortion are the same phenomenon. The reference to 'telephoto' and 'wide angle' there is misleading - it has nothing to do with the focal lengths, only the distance. But longer lenses are usually used at longer distances, and wide lenses are usually used at closer distances (think of framing a person for a portrait), thus the erroneous association with a lens type when it's really the commonly used distances for those lenses that is the cause of both types of perspective distortion.

Regardless of whether or not this clarifies what determines perspective, I'm about to enjoy that bottle of Chocolate Stout. ;D
 

Dantana

EOS RP
Jan 29, 2013
230
69
Los Angeles, CA
www.flickr.com
Did you look at the link in my first post? It talks a lot about focal length compression and how it really works. The conclusion is that shooting a subject a certain distance away from it with a wide lens and cropping down gives you pretty much the exact same look/perspective as if you had shot it from the same distance away with a longer lens and not cropped it.

The advantage of using a longer lens obviously though is you now have a photo that has the perspective you were after but is at the full resolution of your camera, compared to shooting wide and cropping, which obviously gives you a lower resolution. But if we're going to get a super high MP camera coming soon, and the 50mm is as good as it is, I'm wondering how much that will matter.
It's not really what I'm referencing. Maybe you are right.Maybe I'm thinking about this wrong.

But, if you look at the image below like it's an overhead view, and you have the angle of view of a narrower lens (orange) and a wider lens (red), framing two subjects in the foreground and 6 subjects further back, and then crop the wider image to the framing of the foreground in the narrower image (blue), the subjects in the background will be different.

AOV.jpg
 

Dantana

EOS RP
Jan 29, 2013
230
69
Los Angeles, CA
www.flickr.com
You're right that you're not thinking of this right. If you frame the subject the same with 50 and 85, you'll be closer with the 50 and the perspective will be different (i.e. the relationship between the foreground and the background will be different). If you shoot with the 50 and 85 at the same distance from the subject, then crop the image from the 50 to match the FoV of the 85, the perspective is the same and the relationship between the foreground and the background will be the same.

This is from a post of mine way back in 2012:
Well, it seems I'm wrong. Sorry for the misinformation.
 

SecureGSM

EOS 6D MK II
Feb 26, 2017
1,135
184
The perspective doesn’t need to be different, since perspective is a function only of distance to subject (i.e. focal length has nothing to do with perspective).

@Kit Lens Jockey, as long as you frame more loosely with the 50 then crop to the tighter framing the 85 would have given, and as long as you don’t want/need the extra MP, you’d be fine with a (potential future) high-res EOS R and the RF 50/1.2L.
Nuh, perspective distortion of50mm lens is vastly different to the one of a 85mm lens. Take a closer headshot with a 50mm lens and you will notice bulging noses and smaller than normal ears.
So, with 50mm lens one can crop to the same angle of view as with 85mm but perspective distortion won’t be.
 

Kit Lens Jockey

EOS 7D MK II
Nov 12, 2016
500
174
Nuh, perspective distortion of50mm lens is vastly different to the one of a 85mm lens. Take a closer headshot with a 50mm lens and you will notice bulging noses and smaller than normal ears.
So, with 50mm lens one can crop to the same angle of view as with 85mm but perspective distortion won’t be.
Nope, again, there's no difference. The key is right in what you said... If you take a closer headshot with a 50mm lens, yes you will notice a different perspective. But if you take a headshot with a 50mm the same distance away as you would have stood to get a head shot with an 85mm lens and then crop it down to be the same framing as an 85, you will get the same flattening effect as the 85 would have given you.

Take the concept to the extreme... If you stood hundreds of feet away from two people standing side by side each other, but with one person standing just a foot or so closer, using a 600mm lens, the two people would appear almost the same distance away. Now stand that same hundreds of feet away but take the photo with a 50mm and then crop down to the same perspective as a 600mm, obviously your resolution would go to crap, but the two people would still look like they were about the same distance away since you were so far away from them when you took the shot. The one person wouldn't magically jump out in front of the other person within that framing just because you shot it with a 50mm. You were still hundreds of feet away when you took the shot. They two people would still look like they were about the same distance away.
 
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neuroanatomist

I post too Much on Here!!
Jul 21, 2010
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Nuh, perspective distortion of50mm lens is vastly different to the one of a 85mm lens. Take a closer headshot with a 50mm lens and you will notice bulging noses and smaller than normal ears.
So, with 50mm lens one can crop to the same angle of view as with 85mm but perspective distortion won’t be.
Sorry, you totally miss the point. The idea is to take the headshot with the 50mm lens from the same distance one would normally shoot a headshot with an 85mm lens, then crop to the FoV of an 85mm lens. Same distance = same perspective = same distortion (or lack thereof, in this case). Perspective (and any distortion associated with it) is determined only by distance to subject. If you don’t understand that, please (re)read my reply to @Dantana above (expand my self-quoted section), the proof is in the beer (bottles).
 

privatebydesign

Would you take advice from a cartoons stuffed toy?
Jan 29, 2011
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785
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I love the repetitive nature of these threads especially when it is so easy for anybody with two lenses or a single zoom lens to prove themselves.

I did this example for a thread here back in 2012 (something like that, I think Neuro did his bottles for the same thread!). Anyway, take two images from the same place with the same settings but different focal length lenses and the perspective is the same. Fact.

_E1V0033-2.jpg


Now this is an extreme example but it proves the perspective issue, the subject (her ears) the tree and the fences way in the background are all the same size in relation to each other. It also illustrates the nature of DOF and how it is different for different focal length lenses when the same aperture number is used.

So given our original idea, if we shot an image with a 50mm f1.2 at f1.2 from the same place we would shoot an 85 f1.2 at f1.2 and then cropped the 50mm image to match the framing that would have been gotten with an 85, the perspective would be identical, and the depth of field slightly more.
 
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privatebydesign

Would you take advice from a cartoons stuffed toy?
Jan 29, 2011
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I'm not sure I understand why the depth of field is different in those examples. I would have thought the depth of field should be the same as well (after accounting for differences in lens designs, such as the number of blades.)
Because the physical size of the aperture is smaller on the 50/17 than the 85/200 so it makes more dof.
 

SecureGSM

EOS 6D MK II
Feb 26, 2017
1,135
184
Understood. I missed the point yes. If the shot was taken from a far and then cropped to 85mm angle of view then you are correct.


Sorry, you totally miss the point. The idea is to take the headshot with the 50mm lens from the same distance one would normally shoot a headshot with an 85mm lens, then crop to the FoV of an 85mm lens. Same distance = same perspective = same distortion (or lack thereof, in this case). Perspective (and any distortion associated with it) is determined only by distance to subject. If you don’t understand that, please (re)read my reply to @Dantana above (expand my self-quoted section), the proof is in the beer (bottles).