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Archive 2008 · Fast Primes - Why The CA's?

mh2000
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p.2 #1 · Fast Primes - Why The CA's?

Why?

If you are interested, do some looking, tests are out there (I'm not making this stuff up). If you are just trying to bate me... I don't really care, I'm not trying to sell you anything... but Leica is known to make lenses that perform near peak even wide open... it just costs you. There are other individual lenses made by other companies that also perform well wide open, but they are usually standout lenses of the line, not a typical example of the philosophy of the entire line...

danmitchell wrote:
mh2000 wrote:
Leica makes a bunch of lenses that are perform nearly peak wide open...

Show me the test charts that demonstrate this.

Nov 24, 2008 at 12:52 AM

Eric Gottesman
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p.2 #2 · Fast Primes - Why The CA's?

No one has mentioned the fact that available light focusing is much better with wider ap. You can get more accurate focus from an 85 1.8 than any of the 70-200 zooms because you are focusing @ 1.8 no matter what aperture you are actually shooting at. Auto focus hunts less with a full stop of light more. With manual focus you can see more as well.

If it's an aperture of 4.0 I want, I'd still prefer to focus at 1.8 and stop the lens down. I wish all my lenses were 1.2! You can stop down a lens, but you can't "stop up".

-Eric

Nov 24, 2008 at 01:11 AM

danmitchell
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p.2 #3 · Fast Primes - Why The CA's?

I am trying to "bait" you (though not bate you... ;-), mainly because I often hear generalizations about "miracle lenses" that turn out to be less than accurate when you follow up on them.

If you are saying that you have heard that Leica lenses perform as well or nearly so wide open as they do at smaller apertures, fine, but do you _know_ this?

There are some Canon lenses that do a good job of fighting off the inevitable IQ decline as you open the aperture to the widest setting: the 135mm f/2 L and the 300 f/2.8 L come to mind. But IQ _will_ decline to some extent at the largest apertures even on these lenses - and accomplishing this feat with the retrofocus design used in SLR wide and ultrawide lenses is tougher.

Dan

mh2000 wrote:
Why?

If you are interested, do some looking, tests are out there (I'm not making this stuff up). If you are just trying to bate me... I don't really care, I'm not trying to sell you anything... but Leica is known to make lenses that perform near peak even wide open... it just costs you. There are other individual lenses made by other companies that also perform well wide open, but they are usually standout lenses of the line, not a typical example of the philosophy of the entire line...

danmitchell wrote:
mh2000 wrote:
Leica makes a bunch of lenses that are perform nearly peak wide open...

Show me the test charts that demonstrate this.

Nov 24, 2008 at 05:43 AM

Lance Couture
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p.2 #4 · Fast Primes - Why The CA's?

danmitchell wrote:
I am trying to "bait" you (though not bate you... ;-),

*cough*

Nov 24, 2008 at 06:12 AM

makron
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p.2 #5 · Fast Primes - Why The CA's?

danmitchell wrote:
I am trying to "bait" you (though not bate you... ;-), mainly because I often hear generalizations about "miracle lenses" that turn out to be less than accurate when you follow up on them.

If you are saying that you have heard that Leica lenses perform as well or nearly so wide open as they do at smaller apertures, fine, but do you _know_ this?

....

These "miracle lenses" do exist. You don't have to take my words for it. Just get one of them, test it and see for yourself if you do not believe in the tests available in the internet.

For a start you can try out, the Leica-R 90mm/2.0 Apo Asph or Leica-R 100mm/2.8 Apo.

Lens design is always a compromise. Different companies design lenses with different priorities. Many lens designers choose to sacrifice wide open performance for other parameters.

Nov 24, 2008 at 06:13 AM

Ariel Bravy
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p.2 #6 · Fast Primes - Why The CA's?

Lance Couture wrote:
I'm just thinking a loud here, but I have been wondering lately what the point of using fast primes is, when they usually suffer from CA's and lack of sharpness when wide open?

Rumor has it that there's more to photography than sharpness and CA, especially outside of gear boards.

Them's just rumors though.

Nov 24, 2008 at 06:45 AM

mh2000
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p.2 #7 · Fast Primes - Why The CA's?

Ok, it is both. I am not a lens tester. I hear about Leica lenses in general, but my experience is mainly with the Summicron 50 vs. the 4 Canon non-L 50's. I've seen plots and examples to back up the other len generalization though. Yes, the Canon 135L is a wonderful lens, but their 35's and 50's are only ok IMO. With my Leica lenses I never feel I have to stop down to get really good IQ, with my Canon lenses I do... that is what I know.

I would add the TS-E 90 to your short list of superb Canon lenses... that lens is also fantastic wide open IMO.

danmitchell wrote:
I am trying to "bait" you (though not bate you... ;-), mainly because I often hear generalizations about "miracle lenses" that turn out to be less than accurate when you follow up on them.

If you are saying that you have heard that Leica lenses perform as well or nearly so wide open as they do at smaller apertures, fine, but do you _know_ this?

There are some Canon lenses that do a good job of fighting off the inevitable IQ decline as you open the aperture to the widest setting: the 135mm f/2 L and the 300 f/2.8 L come to mind. But IQ _will_ decline to some extent at the largest apertures even on these lenses - and accomplishing this feat with the retrofocus design used in SLR wide and ultrawide lenses is tougher.

Dan

mh2000 wrote:
Why?

If you are interested, do some looking, tests are out there (I'm not making this stuff up). If you are just trying to bate me... I don't really care, I'm not trying to sell you anything... but Leica is known to make lenses that perform near peak even wide open... it just costs you. There are other individual lenses made by other companies that also perform well wide open, but they are usually standout lenses of the line, not a typical example of the philosophy of the entire line...

danmitchell wrote:
mh2000 wrote:
Leica makes a bunch of lenses that are perform nearly peak wide open...

Show me the test charts that demonstrate this.

Nov 24, 2008 at 03:03 PM

jjlphoto
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p.2 #8 · Fast Primes - Why The CA's?

Here is a recent thread dealing with the 35L and CA.
http://www.fredmiranda.com/forum/topic/706750/0#6371754

Nov 24, 2008 at 03:45 PM

danmitchell
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p.2 #9 · Fast Primes - Why The CA's?

Steve:

Thanks for the links. I checked the first one in the list, for which Leica claims "exemplary" performance at f/2.8 (wide open) on this lens. The MTF charts are interesting and it certainly looks like a fine lens... but, as expected, it is "less exemplary" (to make up my own description) wide open at f/2.8.

Note to those who think I'm pixel peeping. Actually, the opposite is true. I understand that lenses exhibit "personalities" that include their performance wide open, CA, etc. - and I'm just fine with that. One does not need a so-called perfect lens (an imaginary being only) to create fine photographs, and I focus far more of my energies on trying to make the best use of the equipment that I have than on searching for an optical holy grail.

Take care,

Dan

Steve Spencer wrote:
Hi Dan,

Click on the links below and then click on the technical data link on the right side. A pdf including the mtfs for these lenses should open in your browser:

http://en.leica-camera.com/photography/r_system/lenses/3797.html

http://en.leica-camera.com/photography/r_system/lenses/3804.html

http://en.leica-camera.com/photography/r_system/lenses/3809.html

http://en.leica-camera.com/photography/r_system/lenses/3806.html

http://en.leica-camera.com/photography/r_system/lenses/3807.html

Although all these lenses are nearly peak wide open, none of them are superfast for the focal lengths wide open. They are all excellent lenses, but you pay a lot for them even used.

Nov 24, 2008 at 03:48 PM

danmitchell
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p.2 #10 · Fast Primes - Why The CA's?

makron wrote:
These "miracle lenses" do exist.

Nah. I've seen "miracle photographs," but never a "miracle lens." :-)

Dan

Nov 24, 2008 at 03:51 PM

Shuko
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p.2 #11 · Fast Primes - Why The CA's?

Steve Spencer wrote:
Although all these lenses are nearly peak wide open, none of them are superfast for the focal lengths wide open. They are all excellent lenses, but you pay a lot for them even used.

Well, we are talking about fast lenses here, not f2-4 lenses. Leicas are nice lenses, but L's do just fine at f2-4.

Nov 24, 2008 at 03:56 PM

coolhat
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p.2 #12 · Fast Primes - Why The CA's?

I am pretty much clueless about lens design, but couldn´t a lens manufacturer easily design a "perfect wide open" lens by just making the maximum aperture a stop or two smaller than necessary. For example, Canon could take their EF 50/1.4, restrict the aperture to 2.8 and voila: an EF 50/2.8 that performs flawlessly wide open!

Conversely, if Canon were to design a, say, 50/1.4 that peaked at wide open, people would start to complain why is it not possible to use it at 1.2 or even 1.0. I think most photographers would rather have the option to use a soft 1.0 than no 1.0 at all...

Nov 24, 2008 at 04:42 PM

Lance Couture
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p.2 #13 · Fast Primes - Why The CA's?

Ariel Bravy wrote:
Rumor has it that there's more to photography than sharpness and CA, especially outside of gear boards.

Them's just rumors though.

Like I said, I was just thinking aloud.

I really like shooting with my primes, and would own more if I could afford them. I just find it really frustrating taking a picture outdoors with my 85/1.8 wide open and having everything outlined in purple...

Nov 24, 2008 at 04:48 PM

kidtexas
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p.2 #14 · Fast Primes - Why The CA's?

A couple points to make:

- a larger aperture lens is harder to design and generally performs worse than a smaller aperture lens - f/1.4 lens will generally perform poorer at all apertures than an f/2.8 lens. The caveat here is that some manufactures put WAY MORE money and time into designing their fast lens then they do the slow one, thus the slower lens performs worse. This just means the slow lens was a poor design. Look at a company like Leica which offers 50mm lenses in f/1.0, f/1.4, f/2.0, and f/2.8 (now f/2.5). The newest f/1.4 lens is a beast, sure, but the much older designed f/2.0 is comparable. Thus if you really want a the best 50 at 1.4, then ask a company to sink a bunch of money into designing a 50/1.4 that is designed to operate at 1.4 with max performance.

- telephoto lenses are typically easier to design. Not knocking Canon (I like them) but to hold up the 135/2 against the 24/1.4 is kind of unfair. It SHOULD be a better lens because its easier to design. Notice its also cheaper.

- not all CA's can be corrected for in Photoshop, if I understand correctly.

- Most manufacturer's normal and wide lenses do not perform best wide open, or any where near 'best'. This is less of an issue with telephotos. Canon's 50/1.4 is a decent performer wide open, but stopped down is much better. To reach that comparable level of performance wide open would cost a lot more money. Again, look at Leica. Do you want to pay $3500 for a 50/1.4 that performs close to its maximum ability wide open? It doesn't even have autofocus! Sure, Canon could have made a better 50/1.2L. They could have increased sharpness at f/1.2 and they could have designed out the focus shift. It probably would have cost a lot more too.

- Lens size is one big constraint on design. Look at the Sigma 50/1.4. Better AND larger than the Canon 50/1.4. Also look a the Leica and Zeiss offerings in M-mount. Even if you agree that they have the same performance for a given lens and aperture, the Leica offerings tend to be smaller (and harder to design and more expensive as a result).

- Canon SLRs (and most other SLRs) focus wide open ALWAYS. You can focus stopped down with the DOF preview button pressed. Thus the lenses don't focus 'better' at smaller apertures. What's likely going on is the extended DOF at smaller apertures is covering up the focus error, or to think of it another way, the very shallow DOF wide open emphasizes focusing errors.

This is a great page to read that talks about lens optics.

Nov 24, 2008 at 05:04 PM

Lance Couture
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p.2 #15 · Fast Primes - Why The CA's?

Great reply!

Thanks!

Nov 24, 2008 at 05:16 PM

michael49
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p.2 #16 · Fast Primes - Why The CA's?

The biggest issue I've had with fast primes is getting the focus right given the very narrow DOF involved.

Many times images are soft not due to lens sharpness, but due to the focus being just slightly off, which is so common at large aperatures.

My 85 1.8 is plenty sharp enough for me wide open; and a little USM can be your best friend. And I can fix the CA fairly easily in most cases.

Nov 24, 2008 at 05:24 PM

Steve Spencer
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p.2 #17 · Fast Primes - Why The CA's?

Steve Spencer wrote:
Hi Dan,

Click on the links below and then click on the technical data link on the right side. A pdf including the mtfs for these lenses should open in your browser:

http://en.leica-camera.com/photography/r_system/lenses/3797.html

http://en.leica-camera.com/photography/r_system/lenses/3804.html

http://en.leica-camera.com/photography/r_system/lenses/3809.html

http://en.leica-camera.com/photography/r_system/lenses/3806.html

http://en.leica-camera.com/photography/r_system/lenses/3807.html

Although all these lenses are nearly peak wide open, none of them are superfast for the focal lengths wide open. They are all excellent lenses, but you pay a lot for them even used.

danmitchell replied:
Steve:

Thanks for the links. I checked the first one in the list, for which Leica claims "exemplary" performance at f/2.8 (wide open) on this lens. The MTF charts are interesting and it certainly looks like a fine lens... but, as expected, it is "less exemplary" (to make up my own description) wide open at f/2.8.

Note to those who think I'm pixel peeping. Actually, the opposite is true. I understand that lenses exhibit "personalities" that include their performance wide open, CA, etc. - and I'm just fine with that. One does not need a so-called perfect lens (an imaginary being only) to create fine photographs, and I focus far more of my energies on trying to make the best use of the equipment that I have than on searching for an optical holy grail.

Take care,

Dan

Hi Dan,

I guess it depends what one means by near peak performance. When I look at the MTFs for these lenses that compare their performance wide open with their performance at peak performance I am stuck by how similar the graphs are. While it is true that wide open performance isn't as good as peak performance, by definition that has to be true. So saying that the lenses are less exemplary than peak performance seems basically tautological. If you visit the alternative gear forum you will see that people report that when using these lens they make decisions solely based on depth of field and don't worry about how aperture affects image quality. That is quite different than how many people use other lenses, in which a trade off between image quality and depth of field considerations seem to often be an issue.

It seems to me that the OP is concerned about exactly that sort of trade off. Leica seems to have made a bit of different lens design decision. They have made lenses that are often a stop slower than some of their competitors, but that have near peak performance or exemplary performance if you prefer wide open and virtually no CA. It seems to me these sort of lens might potentially appeal to the OP. Of course there are reason to not be interested in these Leica lenses. First they are quite expensive. Second they are manual focus only lenses. Third, on a Canon camera adjusting the aperture for metering and focus can be cumbersome. Fourth, did I mention they are very expensive. They certainly aren't miracle lenses, but in my view they do offer a different sort of trade off that some might prefer.

Best wishes,

Steve

Nov 24, 2008 at 05:44 PM

mh2000
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p.2 #18 · Fast Primes - Why The CA's?

this is exactly what I was going to say! When shooting a Leica lens I don't worry, but when shooting nearly every Canon prime lens I have owned, it is/was almost always a factor... some photos just demand impeccable IQ, others don't... (of course, generally the better the photo, the less it relies on IQ).

but also, I recognize the trades and Canon makes some great stuff for the price... and with people already complaining about the price for the Zeiss Distagon in Canon mount without even seeing samples... shows all the noise about wanting Canon to produce really great expensive lenses is really just noise... people don't *really* want to pay the price.

>>...people report that when using these lens they make decisions solely based on depth of field and don't worry about how aperture affects image quality...

Nov 25, 2008 at 12:30 AM

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