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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
Thread started 18 Jul 2012 (Wednesday) 05:44
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Glass Question

 
HunterW
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Jul 18, 2012 05:44 |  #1

I was reading a few forms about maximum resolution of current lenses and how sensors are starting to out resolve lenses
I am assuming resolution is the same this as sharpness so that begs the question (for me at least)

other than sharpness what other characteristics are in glass?

it seems to me coming from a P&S world where everything is about megapickels and then coming into the DSLR world all the focus is about how sharp the glass is

it seems like there should be something else like:
a lens may be as sharp as a tack but it doesnt turn everything the perfect shade of blue and that blue is what makes good photos :)

I hope I got the idea of my question across

thanks
Hunter


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Sorarse
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Jul 18, 2012 06:08 |  #2

You've pretty much hit the nail on the head. Sharpness is one thing, but colour rendition and contrast also contribute to how well a lens performs.


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HunterW
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Jul 18, 2012 15:15 |  #3

Ok cool
what lenses are not inherently sharp but have good contrast and color rendition?
how would you measure contrast and color rendition?


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Rocky ­ Rhode
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Jul 18, 2012 16:01 as a reply to  @ HunterW's post |  #4

A philosopher once said “you get what you pay for”


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HunterW
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Jul 18, 2012 16:06 |  #5

Which is ironic becuase well known historic philosophers hardly ever got paid for their philosophy


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gonzogolf
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Jul 18, 2012 16:22 |  #6

HunterW wrote in post #14736162 (external link)
Which is ironic becuase well known historic philosophers hardly ever got paid for their philosophy

But we remember them and not their brothers. As was mentioned above you mostly get what you pay for, its even more so when you are buying zooms. The best strategy is to decide on a focal length/range and then investigate options within that range. I have to admit that I still focus on sharpness first because color and contrast can and often is manipulated and corrected in post processing. Sharpness can be manipulated to a minor degree but sharpening a soft lens is never satisfying. Another factor to consider is bokeh, or the quality (NOT QUANTITY) of the blurred area in an out of focus image. The construction of the aperture blades can make a difference whether the bokeh of a lens is smooth, or somewhat splotchy.




  
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Rocky ­ Rhode
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Jul 18, 2012 16:45 as a reply to  @ gonzogolf's post |  #7

Budget is something that only you can decide too; while many will tell you that you need to invenst in only "L" lenses, others will advise different.

Once you have determined what style of photography really excites you, and have an established budget to work with, the folks here will be able to really help you assess what is best for your needs.


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Maddscientiskt
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Jul 18, 2012 16:50 |  #8

HunterW wrote in post #14733559 (external link)
I was reading a few forms about maximum resolution of current lenses and how sensors are starting to out resolve lenses
I am assuming resolution is the same this as sharpness so that begs the question (for me at least)

other than sharpness what other characteristics are in glass?

it seems to me coming from a P&S world where everything is about megapickels and then coming into the DSLR world all the focus is about how sharp the glass is

it seems like there should be something else like:
a lens may be as sharp as a tack but it doesnt turn everything the perfect shade of blue and that blue is what makes good photos :)

I hope I got the idea of my question across

thanks
Hunter

I believe I understand your question. Yes absolutely, there is so much more to a lens than sharpness! I believe sharpness tends to be the first place to look when examining a new lens, I'm guilty of it too. Color rendition, resolving power, and contrast to say a few. As said above so much can be done to color in post processing RAW images. However, color is very important in that it creates contrast in images. The point of most contrast is usually where the eye goes first in a photograph. Contrast is also linked to the resolution as well, Luminous Landscapes has a good explanation of this.( http://www.luminous-landscape.com …s/understanding​-mtf.shtml (external link) ). At any rate, resolution and contrast ratio can help account for some of the different looks associated with different brands of lenses, for example your Ziess lens and its unique look. Most of it is personal preference as far as look goes no matter what anyone says. But it is a difference none the less. At the end of the day if you throw a L on your camera, you can't go too wrong :lol:!

Hope this helps, Cheers and Shoot Well!:)




  
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dscri001
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Jul 18, 2012 17:07 |  #9

It's all about light rays. How well a piece of glass can converge light rays to a point will determine how well it performs. It influences things like how well it resolves to detail and how well it reproduces color. I think 'sharpness' is mostly subjective. When light rays do not converge properly you get aberrations, softness, poor contrast, etc. Things that make glass better are mostly in its tolerances and material. Ever hear about what happened to the hubble when it first launched?


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MotorPro
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Jul 18, 2012 17:12 |  #10

Rocky Rhode wrote in post #14736132 (external link)
A philosopher once said “you get what you pay for”

and sometime your just throwing money away




  
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Jul 18, 2012 18:47 as a reply to  @ MotorPro's post |  #11

Long with sharpness, there is contrast, color rendition (both mentioned), chromatic abberation (CA), and distortion (or lack thereof).

sensors are starting to out resolve lenses

This then leads to the question - At what point is the additional resolution useless? There is a point where the eye can no longer see any difference.

It used to be that the film was the weakest link in a photograph. Then it was MP. It seems like what had been the strongest link (glass) is going to become the weakest link. While R&D is great, how much better can they make a piece of glass (or plastic) to allow light to pass through then when they are now?


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JeffreyG
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Jul 18, 2012 20:51 |  #12

HunterW wrote in post #14735903 (external link)
what lenses are not inherently sharp but have good contrast and color rendition?
how would you measure contrast and color rendition?

The 50L comes to mind as a lens that is not especially sharp but which excels in most other categories. The 50L is a reasonably sharp lens, but when it is compared to the other 'L' series primes from Canon it isn't quite in the same league on that one parameter.

But on several other measures, the 50L is quite excellent. Performance aspects of lenses that may or may not matter to every photographer are:

Contrast - This is actually measured in MTF charts and contributes to the apparent sharpness of the image. Excellent in the 50L

Color - can be measured against a color board for accuracy, although accuracy isn't always what photographers are interested in. Some people just like the way certain lenses render color.

Distortion - bending of lines that should be straight. Most primes are good for this, many zooms have issues, especially wide zooms that have large zoom ranges.

Flare - Bright lights in a scene can lead to ghosting flare or veiling flare. The 50L (for example) resists this better than most other 50mm primes.

Vignetting - Heavy in the 50L, but this is typical of very fast lenses.

Coma - distortion in corners.

Along with these optical performance measures, lenses are also judged by how well their AF system works (accuracy, speed, low light etc) as well as how nicely they are built.


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HunterW
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Jul 20, 2012 02:04 |  #13

thanks for your guys input it very interesting and exactly what i wanted to know!
i have one more semi related question
is low light AF performance the lens or the camera or both?


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pyrojim
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Jul 20, 2012 02:22 |  #14

dscri001 wrote in post #14736438 (external link)
It's all about light rays. How well a piece of glass can converge light rays to a point will determine how well it performs. It influences things like how well it resolves to detail and how well it reproduces color. I think 'sharpness' is mostly subjective. When light rays do not converge properly you get aberrations, softness, poor contrast, etc. Things that make glass better are mostly in its tolerances and material. Ever hear about what happened to the hubble when it first launched?

The optical engineer I am working with met the guy who fixed hubble- he is apparently super chill/down to earth/awesome.

My current job is to develop an error model for an optical system and let me tell you... Tolerances are such a B!TCH!!!!


Some of us REALLY take the lenses we have for granted!


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Kolor-Pikker
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Jul 20, 2012 04:07 |  #15

HunterW wrote in post #14743310 (external link)
thanks for your guys input it very interesting and exactly what i wanted to know!
i have one more semi related question
is low light AF performance the lens or the camera or both?

Both. The 135L is one of Canon's fastest-focusing lenses, and will be fast regardless of the camera, but mounting it on a 1-series or 5D3 will definitely show improvement. Counter-wise, the 85L is quite slow, and mounting it on a camera with a top-shelf AF system like the 1Dx or 5D3 will improve accuracy, but not necessarily speed.

Most AF sensors typically lock off their cross points to lenses slower than f/2.8, but this isn't always a detriment as the 70-200 f/4 IS is still one of the fastest-focusing lenses Canon makes. The new f/2.8 IS II lens may be a hair faster, but you're counting the RPMs on F1 race cars at this point.


Returning the the previous topic a bit, one occasionally over-looked point of having a "better" lens is the maximum aperture, because sometimes money simply buys you better physics. It's one thing to simply have a lens that goes really wide open but looks like crap, and another thing if the lens can maintain a fast aperture and still render a razor-sharp image. The 24-70 f/2.8 II and 70-200 f/2.8 IS II are both super-pricy lenses, but changing the aperture on them should only be considered for depth-of-field; as they will be completely free of any aberrations, loss of sharpness, and so on, even at f/2.8.


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