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03-12-2018, 10:44 PM   #1
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A larger database for Lens Resolutions?

I stumbled upon this link in a previous thread; Measured Resolution Numbers

I actually tried shooting at F8 predominately with my FA 50mm 1.4 (determined to be the 'best aperture') and was really encouraged by the results. It made me think how the MTP mode in the camera bodies is supposed to (when pressing green button) take the lens to its best aperture, but I don't think it really does, its pretty much always F5.6 regardless of the lens attached. However this chart might be very helpful and reliable, I wondered if any more databases like this have been done, perhaps involving even more lenses? What's peoples thoughts on charts like this?

Cheers,

Bruce

03-12-2018, 11:02 PM   #2
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QuoteOriginally posted by BruceBanner Quote
It made me think how the MTP mode in the camera bodies is supposed to (when pressing green button) take the lens to its best aperture, but I don't think it really does, its pretty much always F5.6 regardless of the lens attached.
MTF mode stops down the lens 1 stop from wide open, unless the MTF aperture counter interact with proper exposure settings. For instance if for ISO100 1/100th shutter speed the ambient light is such that proper exposure is achieved at aperture f5.6, when you enable MTF priority in P mode, the camera will still stop down the lens to f5.6 regardless of its max aperture and it will be so regardless of the lens model you are using. You could set the exposure compensation to +1ev and see that aperture is stopped down to f4 with a FA 50 1.4 , but if your lens was a DA17-70 f4, then the MTF aperture would be set to f5.6...

Last edited by biz-engineer; 03-12-2018 at 11:07 PM.
03-12-2018, 11:24 PM   #3
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QuoteOriginally posted by biz-engineer Quote
MTF mode stops down the lens 1 stop from wide open, unless the MTF aperture counter interact with proper exposure settings. For instance if for ISO100 1/100th shutter speed the ambient light is such that proper exposure is achieved at aperture f5.6, when you enable MTF priority in P mode, the camera will still stop down the lens to f5.6 regardless of its max aperture and it will be so regardless of the lens model you are using. You could set the exposure compensation to +1ev and see that aperture is stopped down to f4 with a FA 50 1.4 , but if your lens was a DA17-70 f4, then the MTF aperture would be set to f5.6...
My bad, I can't recall where I read about MTF but I thought it was something to do with prioritising the quality/sharpness of the lens attached (whereas the other modes prioritised shutter speed and aperture etc).

Nonetheless, do we know of any other charts like this?
03-12-2018, 11:25 PM   #4
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... that said, f4 and f5.6 are the aperture settings where your FA 50 1.4 will be delivering the sharpest pictures.

03-13-2018, 12:01 AM   #5
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QuoteOriginally posted by biz-engineer Quote
... that said, f4 and f5.6 are the aperture settings where your FA 50 1.4 will be delivering the sharpest pictures.
That's why I found that chart I linked interesting, they chose F8 (for the FA50mm1.4), I usually don't move up that far but I have to say I was really impressed with the results, I think it does trump F4-5.6.
03-13-2018, 02:06 AM   #6
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QuoteOriginally posted by BruceBanner Quote
That's why I found that chart I linked interesting, they chose F8 (for the FA50mm1.4), I usually don't move up that far but I have to say I was really impressed with the results, I think it does trump F4-5.6.
Mind you that chart is from FF / Film days. So maybe its possible that on a FF camera you may get best average resolution across the sensor at f8 (even if centre peaks at around f5.6 say)?
03-13-2018, 07:05 AM - 2 Likes   #7
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I have a few websites that when put together offer a lot of information regarding sharpness.


DXO - Use the "Measurements" -> "Field Map" view.
Camera Lens Database - DxOMark

ePhotoZine
Photography Equipment Reviews

Lenstip
LensTip.com - lens review, lenses reviews, lens specification - LensTip.com

Optical Limits
Pentax K Lens Tests

Photo Review
Lenses - Photo Review

You'll quickly see that f/8 is rarely the most optimal f-stop for ultimate sharpness. Sometimes we get extra depth of field mixed up with greater sharpness. Center sharpness in most lenses seem to peak at around f/4 - f/5.6. Edge sharpness may continue to increase through f/8 before everything starts to tumble.

I'm sure it would be possible to scour these sites and collate some summary data.

Sharpness is only one measure of performance. Be sure to check if the lenses suffer from other aberrations like coma, flare, distortion, etc in "everyday" shooting scenarios. They all impact our perception of sharpness.
03-13-2018, 07:14 AM - 1 Like   #8
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I'd love to see a few more folks adopt Photozone's method of displaying lens sharpness...



Best center sharpness, ƒ4
Best edge to edge sharpness ƒ5.6

ƒ8 will be sharpest only if you need the depth of field to keep part of your subject sharp. But ƒ8 is definitely a great compromise solution if you just want to set it and forget it.

03-13-2018, 07:32 AM - 1 Like   #9
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MTF mode on my PZ-1 did not just stop down 1 stop from wide open. It required a lens with data pin and mtf data (FA and later) In that mode the lens specific best f stop for resolution was preferred.

Here is a discussion about this from the past:

MTF program line | Photo.net Photography Forums
03-13-2018, 07:54 AM   #10
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QuoteOriginally posted by BruceBanner Quote
What's peoples thoughts on charts like this?
The big problem I've found with almost all of these resolution charts and databases
is that they're only done for one particular image distance,
typically 100 times the focal length, say 3.5 m (11.5 ft) for a 35mm lens.

So lenses like the Pentax 24/2.8 K or A will look good on the charts,
while they are much softer at landscape distance.

OTOH, the Zeiss ZK 25/2.8 looks poorer on the charts,
but is then really sharp for landscapes.

Schneider-Kreuznach are one of the very few manufacturers
who will give you MTF charts for a fuller range of focus distances.
03-13-2018, 12:26 PM   #11
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QuoteOriginally posted by 6BQ5 Quote
I have a few websites that when put together offer a lot of information regarding sharpness.


DXO - Use the "Measurements" -> "Field Map" view.
Camera Lens Database - DxOMark

ePhotoZine
Photography Equipment Reviews

Lenstip
LensTip.com - lens review, lenses reviews, lens specification - LensTip.com

Optical Limits
Pentax K Lens Tests

Photo Review
Lenses - Photo Review

You'll quickly see that f/8 is rarely the most optimal f-stop for ultimate sharpness. Sometimes we get extra depth of field mixed up with greater sharpness. Center sharpness in most lenses seem to peak at around f/4 - f/5.6. Edge sharpness may continue to increase through f/8 before everything starts to tumble.

I'm sure it would be possible to scour these sites and collate some summary data.

Sharpness is only one measure of performance. Be sure to check if the lenses suffer from other aberrations like coma, flare, distortion, etc in "everyday" shooting scenarios. They all impact our perception of sharpness.
I think this is what I experienced with my weekend of f8 shooting with the FA50mm, a lot of it was landscape work, infinity focus etc. Thanks for the links and comments!

QuoteOriginally posted by normhead Quote
I'd love to see a few more folks adopt Photozone's method of displaying lens sharpness...



Best center sharpness, 4
Best edge to edge sharpness 5.6

8 will be sharpest only if you need the depth of field to keep part of your subject sharp. But 8 is definitely a great compromise solution if you just want to set it and forget it.
Awesum, thanks norm. Just quickly can I ask on that chart what 'MTF50 in LW/PH' stands for?

I noticed a couple of my MF lenses 24-28mm ones, F8 is seen as the 'street mode' or best option to get 'everything' in acceptable focus (like a hyperfocal thing). So perhaps with the FA50mm 1.4, they (the original link folk) chose f8 because although it does drop in sharpness (centre and border) it will have more 'stuff' in focus for the shot?

QuoteOriginally posted by UncleVanya Quote
MTF mode on my PZ-1 did not just stop down 1 stop from wide open. It required a lens with data pin and mtf data (FA and later) In that mode the lens specific best f stop for resolution was preferred.

Here is a discussion about this from the past:

MTF program line | Photo.net Photography Forums
More reading material, ta!

QuoteOriginally posted by lytrytyr Quote
The big problem I've found with almost all of these resolution charts and databases
is that they're only done for one particular image distance,
typically 100 times the focal length, say 3.5 m (11.5 ft) for a 35mm lens.

So lenses like the Pentax 24/2.8 K or A will look good on the charts,
while they are much softer at landscape distance.

OTOH, the Zeiss ZK 25/2.8 looks poorer on the charts,
but is then really sharp for landscapes.

Schneider-Kreuznach are one of the very few manufacturers
who will give you MTF charts for a fuller range of focus distances.
The plot thickens...

Cheers everyone for the input, lots of reading for Bruce this weekend
03-13-2018, 12:34 PM - 1 Like   #12
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It is also important to note that if the MTF program line is working as it was originally intended - the actual f/stop may vary from the best f/stop of the lens - it will attempt to get as close to that as the exposure permits but will also take other factors of exposure into account - it is a line that it tries to adjust to - not a single fixed data point. However I have not done any real experimentation to test this in a long time (back since the PZ-1 days I'd wager... .)
03-13-2018, 12:51 PM - 1 Like   #13
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QuoteOriginally posted by BruceBanner Quote
Just quickly can I ask on that chart what 'MTF50 in LW/PH' stands for?
You can ask, but I have no idea.... all I know is it's some measurement standard, and that there are others. There are explanations on the web, and I've read some of them, but it's still greek to me.
03-13-2018, 01:07 PM - 2 Likes   #14
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(I wonder why the amount of full quotes are increasing - this makes threads really hard to follow)

QuoteOriginally posted by BruceBanner Quote
Just quickly can I ask on that chart what 'MTF50 in LW/PH' stands for?
Line width per picture height
Resolution measurement and its units
Sharpness: What is it and how is it measured? - imatest
03-13-2018, 01:38 PM   #15
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QuoteOriginally posted by angerdan Quote
(I wonder why the amount of full quotes are increasing - this makes threads really hard to follow)


Line width per picture height
Resolution measurement and its units
Sharpness: What is it and how is it measured? - imatest
Prolly cause I'm lazy, lacking caffeine and in a rush before heading out the door this morning for work (hey I do try and Bold stuff in the quotes tho!)
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