September 23, 2014, 08:39:58 AM

Author Topic: What is the "sweetspot" for the 100mm f/2.8L IS Macro & the 70-200mm f/4L USM  (Read 14093 times)

jdramirez

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I bought two lenses and I prefer to take most of my shots near or on the mythical sweetspot in regards to aperture.  With the presumption of sufficient light, for my 50mm f/1.4 I try to stay between 2.8 and 4.0.  For my 24-105mm f/4 I make an effort to approach f/8, but that isn't always an option.

So that raises the aforementioned question.  What aperture range is the 100mm and the 70-200 the sharpest?  And don't hesitate to tell me that I was wrong about the 50 and 24-105... if indeed I'm way off.

Thanks a bunch.
Upgrade  path.->means the former was sold for the latter.

XS->60D->5d Mkiii:18-55->24-105L:75-300->55-250->70-300->70-200 f4L USM->70-200 f/2.8L USM->70-200 f/2.8L IS Mkii:50 f/1.8->50 f/1.4->100L->85mm f/1.8 USM-> 8mm ->100L & 85L

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bdunbar79

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I bought two lenses and I prefer to take most of my shots near or on the mythical sweetspot in regards to aperture.  With the presumption of sufficient light, for my 50mm f/1.4 I try to stay between 2.8 and 4.0.  For my 24-105mm f/4 I make an effort to approach f/8, but that isn't always an option.

So that raises the aforementioned question.  What aperture range is the 100mm and the 70-200 the sharpest?  And don't hesitate to tell me that I was wrong about the 50 and 24-105... if indeed I'm way off.

Thanks a bunch.

Pretty much all of my lenses are sharpest around f/8.  That doesn't mean that lenses aren't sharp at other apertures.  That's just where they are sharpest.
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jdramirez

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Pretty much all of my lenses are sharpest around f/8.  That doesn't mean that lenses aren't sharp at other apertures.  That's just where they are sharpest.

Which lenses do you have?
Upgrade  path.->means the former was sold for the latter.

XS->60D->5d Mkiii:18-55->24-105L:75-300->55-250->70-300->70-200 f4L USM->70-200 f/2.8L USM->70-200 f/2.8L IS Mkii:50 f/1.8->50 f/1.4->100L->85mm f/1.8 USM-> 8mm ->100L & 85L

bdunbar79

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Pretty much all of my lenses are sharpest around f/8.  That doesn't mean that lenses aren't sharp at other apertures.  That's just where they are sharpest.

Which lenses do you have?

All of the ones in my signature file. 
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jdramirez

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Pretty much all of my lenses are sharpest around f/8.  That doesn't mean that lenses aren't sharp at other apertures.  That's just where they are sharpest.

Which lenses do you have?

All of the ones in my signature file.

Silly me.  I guess signatures actually do serve a purpose. Thanks.
Upgrade  path.->means the former was sold for the latter.

XS->60D->5d Mkiii:18-55->24-105L:75-300->55-250->70-300->70-200 f4L USM->70-200 f/2.8L USM->70-200 f/2.8L IS Mkii:50 f/1.8->50 f/1.4->100L->85mm f/1.8 USM-> 8mm ->100L & 85L

bdunbar79

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Pretty much all of my lenses are sharpest around f/8.  That doesn't mean that lenses aren't sharp at other apertures.  That's just where they are sharpest.

Which lenses do you have?

All of the ones in my signature file.

Silly me.  I guess signatures actually do serve a purpose. Thanks.

Haha!  Hey no big deal!
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pdirestajr

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Can I ask why you would want to buy / use a lens that has an adjustable aperture at only the "mythical sweet spot"? Aren't you limiting your creative control?
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Viggo

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I don't absolutely agree that f8 is the sharpest.

I ran a "aperture sharpness test" in focal with all my lenses and the:

24 L II= sharpest at f2,5

35 L II= f3,5

50 L= better at 1,8 than 2,2, sharpest at f5

85 L= f5 (huge drop from f2 to 1,2)

135= f7.1

All lenses showed a fair amount of loss of sharpness any smaller aperture.

I use my lenses at the needed aperture, but I must admit, I use 2,5 with the 24 more now (instead of 1,8-2.0), and the 50 at 1,8
« Last Edit: August 25, 2012, 03:44:46 AM by Viggo »
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candyman

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I don't absolutely agree that f8 is the sharpest.

I ran a "aperture sharpness test" in focal with all my lenses and the:

24 L II= sharpest at f2,5

35 L II= f3,5

50 L= better at 1,8 than 2,2, sharpest at f5

85 L= f5 (huge drop from f2 to 1,2)

135= f7.1

All lenses showed a fair amount of loss of sharpness any smaller aperture.

I use my lenses at the needed aperture, but I must admit, I use 2,5 with the 24 more now (instead of 1,8-2.0), and the 50 at 1,8


Just curious; does that also mean that you now have set the in-camera sharpness setting to "0" (zero) ?
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sheedoe

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35 L II= f3,5
I guess this lens is no longer a rumor then  :P
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Viggo

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35 L II= f3,5
I guess this lens is no longer a rumor then  :P

LOL, yeah sorry about that!
1dx, 24-70 L II, 50 Art, 200 f2.0 L

Viggo

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I don't absolutely agree that f8 is the sharpest.

I ran a "aperture sharpness test" in focal with all my lenses and the:

24 L II= sharpest at f2,5

35 L II= f3,5

50 L= better at 1,8 than 2,2, sharpest at f5

85 L= f5 (huge drop from f2 to 1,2)

135= f7.1

All lenses showed a fair amount of loss of sharpness any smaller aperture.

I use my lenses at the needed aperture, but I must admit, I use 2,5 with the 24 more now (instead of 1,8-2.0), and the 50 at 1,8


Just curious; does that also mean that you now have set the in-camera sharpness setting to "0" (zero) ?

The software sets up the camera with it's own settings, so I'm not sure. But if you sharpen +3 or -3, the difference between apertures would be the same, all would be softer or sharper.
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bdunbar79

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I agree that it depends on the lens, especially zoom lenses.  But you have to sit and think about why.  As you stop down, more and more of the center of the lens is actually being used, until you get so narrow that diffraction comes into play.  As you use more and more of the center, the sharper the images, until diffraction.  It is beyond me how something wider than f/3.2 can be the sharpest aperture on any lens.  I know I explained that very roughly, but it's coffee time :)   
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skitron

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What aperture range is the 100mm and the 70-200 the sharpest?

The 100L and 70-200 f4 don't have the sharpness fall-off that a fast prime would at max aperture.

DxO (see Measurements>Resolution>Field Maps).

And since DxO can be a can of worms at times (Neuro pointed to the 70-200 II which on DxO seems to have totally invalid results), also see TDP. Photozone.de also has these two lenses, with similar results.

I have a 100L and in practical terms it is no different for anything f11 and less. Unlike the two fast primes I have that definitely get sharper >= f2.8.
« Last Edit: August 25, 2012, 11:41:24 AM by skitron »
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jrista

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You can certainly ask other people's opinions about such things, however maximum sharpness is a function of every component in an imaging system, including the sensor. For someone using, say, a Canon 1D IV or 1D X, where the maximum theoretical sensor spatial resolution is less than 100 lp/mm, their best aperture is likely to be higher than someone using say the Canon 7D, which has a maximum theoretical sensor spatial resolution of 116 lp/mm, and could realize better resolution at wider apertures.

Theoretically speaking, most lenses will peak in sharpness at around f/4-f/6, depending on the specific characteristics of the lens. Top-grade professional lenses, such the more expensive Canon L-series lenses, can potentially peak near their maximum aperture, with the top few supertelephoto L-series lenses released in the last few years doing just that (the 300mm, 400mm, 500mm, and 600mm Mark II L-series lenses are all nearly perfect, and most achieve maximum sharpness at their widest aperture, or within 1/3 to 2/3rds of a stop from it.)

If you want to figure out the "sweet spot" for any lens, you can use Reikan FoCal Pro (http://www.reikan.co.uk/focal/focal-pro.html) to do so. It has an Aperture Sharpness tool that takes photos at every aperture, from the narrowest to the widest, and evaluates IQ for each one. I recently ran an evaluation of aperture sharpness for my copy of the 100mm f/2.8 USM Macro lens (after using FoCal Pro to do what I purchased it for...automatically tune AF micro focus adjustment for maximum performance). My test results, after several runs, indicate that f/4.5 is the optimal aperture for this lens (at least with the 7D's 18mp sensor). This should remain true with larger sensors that have lower spatial resolutions as well, such as the 1D X or 5D III.
« Last Edit: August 25, 2012, 11:50:49 PM by jrista »
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