Why won't Canon do a silent upgrade (fix) for the 50L focus shift?

I guess I don't have to explain much about the focus shift issue with the 50L? I think the issue is well known among Canon shooters, so I'll jump straight to my question.

The focus shift problem could be compensated with a floating element system to correct spherical aberration, in addition to the aspherical element already in the 50L design. Take the 85L as example - it has a floating element and aspherical elements, and is 100% free from the dreaded focus shift.

1. Why didn’t Canon include a floating element in the 50L?
2. Since they didn't, then why won't they do a silent upgrade to fix this?

Is it because it would be unfair to those who alredy bought it, or is it because they want to save the fix for a $2300 MK II version?

I dont understand..

Good question.

The focus shift issue is the only think keeping me away from buying this lens, and I don't think I am the only one. I know many who have stoped using or sold their 50L because of the focus shift problems.

And yeah, the answer is probably a $2300 MK2 version in the future.

For the photography I do, this isn't an issue. Selecting aperture is one of the first things I do. I could see this is a problem for landscape photogs that vary aperture settings frequently from a tripod, but my understanding is the focus shift issue only comes into play if you are going from wide open to f/2.8 or higher.

When I used the lens and was shooting test charts, yes I could see the focus shifting. At f/2.8, it back focus less than 1 inch and exhibited less shift at bigger apertures. The DoF at smaller apertures was big enough to compensate for the shifting. Personally, I don't think the focus shift is a huge deal.

Real world photos? Not a single picture was scrapped because of focusing shifting. Canon probably doesn't feel like it's a big enough deal to fix it, at least not until a mk 2 version.

They will probably try to get it right in Mk 2. I dumped mine and got a 24L II. It is razor sharp at f2. Much happier.

I suppose the issue could have been overcome to a degree by making the lens focus at the shooting aperture instead of wide open which would have worked up until f/5.6, this would have had a negative effect on AF speed but would have cured the focus shift.

The focus shift is part of the lens design. It is not a mistake or something the lens designers forgot. The Canon 50 f/1.4, Sigma 50 f/1.4, Zeiss 50 f/1.4 and Canon 50 f/1.2L all suffer from it. The fix (as you've pointed out) is to redesign the lens to follow a "macro" approach with one or more floating elements. The Zeiss 50 f/2 makro-planar for instance does not have this focus shift.

Changing the optical design of the 50L to add the floating element may bring with it a whole host of other issues. At the very least, the cost would go up. It may be that they may not be able to maintain the f/1.2 ratio or sweet bokeh or who knows what.

Tonyz wrote in post #14275450
Good question.

The focus shift issue is the only think keeping me away from buying this lens, and I don't think I am the only one. I know many who have stoped using or sold their 50L because of the focus shift problems.

And yeah, the answer is probably a $2300 MK2 version in the future.

I agree Tonyz, this is the only thing keeping me from investing in this lens as well. Let's see what they do for the Mk II version if there will be such a thing and what price is attached to it.

Funny. It's never ever been a problem for me.

I suspect the "point" of the lens may have been lost on some people.

I was once scared of the focus shift and lack of sharpness. But then I actually started taking real life photos with the lens, and quickly realized how much of an effect an internet forum was having on my lens choices.

By far the softest of my lineup, yet easily produces the most beautiful results.

MatthewK wrote in post #14278803
By far the softest of my lineup, yet easily produces the most beautiful results.

Sorry can't agree with that. Since when beautiful = soft and oof???

I think he wasn't saying the images were the most beatiful because of the softness. He was saying they were more beautiful IN SPITE of it.

In escence, he's saying sharpness isnt EVERYTHING. And that pixelpeeping poisons the mind. He may have a point.

sunking39 wrote in post #14278990
In escence, he's saying sharpness isnt EVERYTHING. And that pixelpeeping poisons the mind. He may have a point.

Oh please! If you don't pixel peep, i doubt anyone can see the difference between the 50 1.4 @ 1.4 compared to the 50L @ 1.2 under normal print size. Hell the difference is minimal at best even when you compare the same shot side by side @ 100%.

When you are paying over $1k for a lens, you bet sharpness is one of the major consideration.

Then again what do i really know...

kin2son wrote in post #14279065
When you are paying over $1k for a lens, you bet sharpness is one of the major consideration.

The 50L is a specialty lens that is optimized for background blur quality. So beyond build quality, flare resistance etc. this is what the premium price is paid for (not sharpness).

There are trade offs in lens design. How much spherical aberration is corrected has a major impact to background blur quality and the 50L is optimized for background blur.
There are other types of specialty lens, where this is adjustable (so you can see that this is not a design fault, rather it's a design trade off):
http://www.stacken.kth​.se/~maxz/defocuscontr​ol/

Thus undercorrected spherical aberration (with the unfortunate focus shift that could and should be easily taken into account/corrected in the body) is inherent to the design of this lens,
please check Figure 4 of the following link (focus plane A vs. C) http://www.bokehtests.​com/Site/About_Bokeh.h​tml,
so to expect that Canon will do a silent change of this behavior indicates that someone has totally missed the point of this lens (which is btw. not sharpness).

What we can expect (and hope) that Canon will someday include an automatic in body correction for the focus shift. Till that the users of the 50L lens has to calculate with this by their own.
If you've found a copy that does less focus shift it means you've found a defective (from the original lens design perspective) copy of the lens...

k1csi wrote in post #14279555
The 50L is a specialty lens that is optimized for background blur quality. So beyond build quality, flare resistance etc. this is what the premium price is paid for (not sharpness)...

I see what you mean, but the same thing can be said about the 85L II and the 135L. These two lenses are also built to blur the background into oblivion, at 1.2 and 2.0.


The difference is that those lenses are still razor sharp while doing their background blur work. So why can't the 50L keep up?