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Lens sharpness chart comparisons


Ruel_Fox Avatar
2 Jul 2019 5:28PM
Can anyone explain how the different lens sharpness scores compare? On some older reviews the grading is from “Poor” up to (and beyond) “excellent” whereas on others it runs from 0 up to, on the example I’ve looked at, 4000.

Any help in comparing the two would be very much appreciated!
dcash29 Avatar
dcash29 18 2.4k England
2 Jul 2019 7:39PM
Your guess is as good as mineWink
KevinEllison Avatar
5 Jul 2019 8:59PM
Think I would prefer user opinions rating from “poor” to “excellent” compared with numbers...but I guess they’re both comparable...big numbers = better than low numbers...! so somewhat agree with dcash29..!
JJGEE Avatar
JJGEE 18 8.1k 18 England
5 Jul 2019 10:18PM
No idea.

And what use do these comparison charts have, especially those MTF ones which I cannot even begin to understand Sad



LenShepherd Avatar
LenShepherd 15 4.7k United Kingdom
6 Jul 2019 9:25AM
You have asked a "minefield" question.

Most tests of the type I think you are referring to are of a very high contrast 1000:1 target - almost never encountered in real world photography.

The targets are usually about 3 feet on the long dimension. This is OK for head and portrait type for photography but may be of little relevance for smaller subjects or landscapes.

Being only a black on white target they may be a poor source of information if a lens does not bring all colours into focus at exactly the same focus distance.

Corner resolution and contrast is never as good as edge or centre, making a number averaging all 3 of little benefit.
It is common to need good performance in a landscape, but not necessarily in a portrait.

Corner performance usually improves, often significantly, as a lens is stopped down.

Most lens have lens aberrations which reduce resolution and contrast at wider apertures and all have diffraction which gradually reduces resolution at very small apertures.

Lens performance often varies with focus distance.

In the era of film it was common to provide resolving power at 1,000:1 contest and at a very low contrast of 1.6:1.
Then each photographer had to guess what the resolving ability was at say a more common photographic subject of 1:125.

A high contrast image with relatively low resolution is often perceived as "sharper" to the human brain than a high resolution with relatively low contrast.

Figures provided can be of some benefit comparing different lenses using that test provided they are tested in exactly the same way.
ephotozine has used Imatest for a few years.

At the end of the day the only way to be sure how a lens performs is for each photographer to test each lens they way they would normally usr it.
JJGEE Avatar
JJGEE 18 8.1k 18 England
6 Jul 2019 10:01AM

Quote:At the end of the day the only way to be sure how a lens performs is for each photographer to test each lens they way they would normally usr it.


I doubt that this is practical..... will my local camera store let me ' try out ' a £12,000 lens to see how it performs Sad

dcash29 Avatar
dcash29 18 2.4k England
6 Jul 2019 12:12PM

Quote:No idea.

And what use do these comparison charts have, especially those MTF ones which I cannot even begin to understand Sad



Why is there any difference?
LenShepherd Avatar
LenShepherd 15 4.7k United Kingdom
6 Jul 2019 9:30PM

Quote:
Quote:At the end of the day the only way to be sure how a lens performs is for each photographer to test each lens they way they would normally use it.


I doubt that this is practical..... will my local camera store let me ' try out ' a £12,000 lens to see how it performs Sad


It depends.
If you are a good customer able to purchase a £12,000 lens it may be possible to arrange a "hands on" with the area sales rep.
I was able to do this with Nikon before the release of both the D850 and the Z7.
saltireblue Avatar
saltireblue Plus
13 14.5k 89 Norway
6 Jul 2019 10:51PM

Quote:
Quote:At the end of the day the only way to be sure how a lens performs is for each photographer to test each lens they way they would normally usr it.


I doubt that this is practical..... will my local camera store let me ' try out ' a £12,000 lens to see how it performs Sad



Yes. My local store where I have been a customer for about 10 years has a “test drive “ facility for registered customers whereby they can have equipment for up to 3 days for a nominal fee.

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