Lenses with wider opening better?

sanj

EOS R5
Jan 22, 2012
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This shows that the 2.8 version of the zoom is better. Is this always the case? Thx.
 

koenkooi

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It depends on how you define 'better', if the f/2.8 is too heavy, too bulky, too expensive or a combination of those for your use case, does it matter if it is slightly sharper?
 

sanj

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Jan 22, 2012
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It depends on how you define 'better', if the f/2.8 is too heavy, too bulky, too expensive or a combination of those for your use case, does it matter if it is slightly sharper?
Yes, my post is about IQ. What I am discovering is that a (picking arbitrary) a 50 mm f1.2 lens will have better IQ at f1.4 than a 50 mm f1.4 lens will have at f1.4. Did not know this.
 

AlanF

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The-Digital-Picture is a great site, the best out there for thoughtful, careful, unbiased analysis, and a mine of information. But, Bryan Carnathan looks at just one copy (or sometimes 2) of a lens, although he does send some back, and his chart comparisons should not be taken too seriously. For example, one that affected my choice once was the 100-400mm II vs 400mm DO II which has the zoom sharper, which is contrary to the many copy analysis on lensrentals and my own experience.

I have had the same experience with other lenses, especially EF-M. Your example is not a good choice anyway as comparing a 14-35 with a 15-35 has too many variables other than just a change in maximum aperture.
 
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sanj

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The-Digital-Picture is a great site, the best out there for thoughtful, careful, unbiased analysis, and a mine of information. But, Bryan Carnathan looks at just one copy (or sometimes 2) of a lens, although he does send some back, and his chart comparisons should not be taken too seriously. For example, one that affected my choice once was the 100-400mm II vs 400mm DO II which has the zoom sharper, which is contrary to the many copy analysis on lensrentals and my own experience.

I have had the same experience with other lenses, especially EF-M. Your example is not a good choice anyway as comparing a 14-35 with a 15-35 has too many variables other than just a change in maximum aperture.
I never questioned Bryan so far...
 

gruhl28

Canon 70D
Jul 26, 2013
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This shows that the 2.8 version of the zoom is better. Is this always the case? Thx.
This is usually the case, but not always. One of the older super-fast Canon 50mm lenses had a reputation for being soft even when stopped down and never being as sharp as the 1.4 when it was stopped down.
 
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AlanF

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This is usually the case, but not always. One of the older super-fast Canon 50mm lenses had a reputation for being soft even when stopped down and never being as sharp as the 1.4 when it was stopped down.
One case I recall where the narrower lens was better than the wider stopped down was the original Canon EF 70-200mm L, where the f/4 at 200mm is slightly sharper than the f/2.8 stopped down to f/4.

 
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Joules

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I never questioned Bryan so far...
Sample variation is not about questioning a reviewer that you like. It's just that each lens is slightly different and depending on the manufacturing, the differences can be more pronounced.

So you really can't look at a comparison like the one you posted where the differences are so small and conclude from it that one lens will definitely be better. You could buy the apparently worse lens and get a great copy, and therefore be lucky, or you could buy the better lens and get a poor copy - or it may be that you are mistaken in assuming which lens is the better one because the reviewer themselves got a great or terrible copy.
 
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neuroanatomist

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Yes, my post is about IQ. What I am discovering is that a (picking arbitrary) a 50 mm f1.2 lens will have better IQ at f1.4 than a 50 mm f1.4 lens will have at f1.4. Did not know this.
Stopping down a lens a bit almost always improves the IQ relative to wide open. That’s evident on MTF charts that show sharpness wide open and at f/8. The same applies to vignetting as well as axial CA.

So in general, comparing an f/2.8 lens stopped down to f/4 with an f/4 lens at maximum aperture will favor the former.

As pointed out, copy variation matters. For zoom lenses, where you are in the range also matters.
 
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AlanF

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Stopping down a lens a bit almost always improves the IQ relative to wide open. That’s evident on MTF charts that show sharpness wide open and at f/8. The same applies to vignetting as well as axial CA.

So in general, comparing an f/2.8 lens stopped down to f/4 with an f/4 lens at maximum aperture will favor the former.

As pointed out, copy variation matters. For zoom lenses, where you are in the range also matters.
The various aberrations of lenses start manifesting themselves at about f/4 and wider, and get worse as the aperture widens. So, in order to build a high class lens that is sharp at f/2.8, f/2, f/1.4 etc, the designers have to work hard to minimise aberrations and I would guess that this extra design effort may help optimise IQ at narrower apertures until diffraction limitations take over. They don't have to work as hard to design a lens that opens only to f/4. If they wanted, they could build a lens of the same optical formula for the narrower lens that would be equivalent to the wider stopped down, but it is cheaper not to, I presume. For wider lenses, they do get sharper as they are narrowed by a couple of stops as you say. For the new generation of high quality lenses of narrow aperture, the f-numbers are above f/4 and they are at their sharpest wide open where aberrations are not present and diffraction is least problematic - the ones I know are the RF 100-500mm f/7.1 and Nikon 500mm f/5.6.
https://opticallimits.com/canon_eos_ff/1102-canonrf100500f4571?start=1

https://www.lenstip.com/540.4-Lens_..._500_mm_f_5.6E_PF_ED_VR_Image_resolution.html
 
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Sporgon

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For the new generation of high quality lenses of narrow aperture, the f-numbers are above f/4 and they are at their sharpest wide open where aberrations are not present and diffraction is least problematic - the ones I know are the RF 100-500mm f/7.1 and Nikon 500mm f/5.6.
https://opticallimits.com/canon_eos_ff/1102-canonrf100500f4571?start=1

https://www.lenstip.com/540.4-Lens_..._500_mm_f_5.6E_PF_ED_VR_Image_resolution.html
TS-E 24/3.5 is another one that comes to mind.
 

sanj

EOS R5
Jan 22, 2012
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I wanted to buy the 70-200 f4 RF and 14-35 f4 RF for lighter travel. I already own the f2.8 of both these zooms. Now I am in two minds. I also wonder if in the real world the slight reduction in IQ will matter....
 

AlanF

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I wanted to buy the 70-200 f4 RF and 14-35 f4 RF for lighter travel. I already own the f2.8 of both these zooms. Now I am in two minds. I also wonder if in the real world the slight reduction in IQ will matter....
If you are going to shoot nearly always at f/4 or narrower with the 2.8, then get the f/4 lens. If you really need the f/2.8 for low light or better bokeh, then get that.
 
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Bdbtoys

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I wanted to buy the 70-200 f4 RF and 14-35 f4 RF for lighter travel. I already own the f2.8 of both these zooms. Now I am in two minds. I also wonder if in the real world the slight reduction in IQ will matter....
I was also thinking about this a while back (I also have the f2.8's and debated the f4's for lightweight usage), however the primary reason I am passing on the f4's at this time is the additional cost of a lens that I already have a superior version of these zoom focal lengths (outside of a slight size/weight difference), where those funds could be better spent on other lenses that could fill gaps in my kit.

I do get it that typically if I need lighter, I most likely don't need f2.8, so the f4 would be fine. And as you mentioned, in the real world the IQ loss would not be as noticeable (but there is a small trade off). However, I don't find the size of the f2.8's to be unwieldy that I 'need' the f4's (the latter is lighter, but not that much to me). However, that being said there is a limit to my size/weight threshold... for example, the 28-70/2 is an awesome lens that exceeds the quality of the 24-70/2.8, but once I used it for a while, I just couldn't see myself using it the majority of the time due to it's size/shape/weight... so I went with the f2.8 instead. But that choice of the 24-70/2.8 was also over the 24-105/4 (there was more to that choice, as there were other lenses in play). Other people limits are different so keep in mind this is just my take.

However, the biggest deciding factor is that I had to be honest with myself if I had both... saying 'when I have to choose to put one of them in my bag, which would I take'.
 
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Bdbtoys

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If you are going to shoot nearly always at f/4 or narrower with the 2.8, then get the f/4 lens. If you really need the f/2.8 for low light or better bokeh, then get that.
This is the recommendation I would give to someone that didn't have either lens. But for someone that already has the 2.8's... I wouldn't recommend duplicating focal lengths in zooms unless the need for a lighter lens really justifies the cost.
 
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sanj

EOS R5
Jan 22, 2012
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I was also thinking about this a while back (I also have the f2.8's and debated the f4's for lightweight usage), however the primary reason I am passing on the f4's at this time is the additional cost of a lens that I already have a superior version of these zoom focal lengths (outside of a slight size/weight difference), where those funds could be better spent on other lenses that could fill gaps in my kit.

I do get it that typically if I need lighter, I most likely don't need f2.8, so the f4 would be fine. And as you mentioned, in the real world the IQ loss would not be as noticeable (but there is a small trade off). However, I don't find the size of the f2.8's to be unwieldy that I 'need' the f4's (the latter is lighter, but not that much to me). However, that being said there is a limit to my size/weight threshold... for example, the 28-70/2 is an awesome lens that exceeds the quality of the 24-70/2.8, but once I used it for a while, I just couldn't see myself using it the majority of the time due to it's size/shape/weight... so I went with the f2.8 instead. But that choice of the 24-70/2.8 was also over the 24-105/4 (there was more to that choice, as there were other lenses in play). Other people limits are different so keep in mind this is just my take.

However, the biggest deciding factor is that I had to be honest with myself if I had both... saying 'when I have to choose to put one of them in my bag, which would I take'.
Yes. However, the combined weight reduction of both these zooms combined is not negligible. I have put up my R5, my prime lenses and 2.8 lenses up for rent in Mumbai, India. If they start renting I would buy the f4. Currently (something we don't like to hear on this forum), the Canon gear rents less than 25% of what Sony rents. Unfortunately.
 

Bdbtoys

R5
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Jul 16, 2020
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Yes. However, the combined weight reduction of both these zooms combined is not negligible. I have put up my R5, my prime lenses and 2.8 lenses up for rent in Mumbai, India. If they start renting I would buy the f4. Currently (something we don't like to hear on this forum), the Canon gear rents less than 25% of what Sony rents. Unfortunately.
It sounds like you really want the f4's and sell/rent your 2.8's which I'm sure you will be happy with. As mentioned... everyone's size/weight threshold is different as well as the need for a large aperture.