Bengt Nyman
Senior Member
Lens manufacturers publish MTF charts describing the contrast performance of a lens as a function of the distance from the image center. They typically do this using test charts with 10 or 30 LP/mm (line-pairs/mm).
Many photographers today wonder how their existing lenses will perform on a new camera, especially on one with a higher resolution sensor. An FF, 36 MP sensor corresponds to 104 LP/mm and a 50 MP sensor corresponds to 144 LP/mm. Testing done with 10 and 30 LP/mm charts are therefore meaningless when it comes to answering these questions.
As it is now, there is an large discrepancy between test results published by Lenscore and those published by DxO. If you believe Lenscore the Nikkor 600mm f/4 is 31% sharper than the Nikkor 85mm f/1.4. If you believe DxO the 85mm lens is 25% sharper than the 600mm, tested on a Nikon D800E.
The relatively new DxO definition of a lens resolution expressed in PMP (Perceptual Megapixel) is limited to its performance on a specific camera and not very useful in predicting the performance of that lens on a different camera.
The only way to know for sure would be if the industry started publishing charts showing the lens image contrast (readability) as a function of test chart line pair density (or test chart MP). Since newer, high resolution sensors correspond to 104 LP/mm (36MP) and 144 LP/mm (50MP), you would like to know how the lens performs at various test chart line pair densities (or test chart MP) up to 144 LP/mm (50 MP). This way you could clearly see at what resolution (in LP/MM or MP) your lens stops producing readable results compared to the resolution potential of your image sensor.
This information would end the arguments between the optimists who think that their existing lenses will give them 45 PMP images from their new 50 MP camera, and the pessimists who think that their new high resolution camera will need all new lenses.
Many photographers today wonder how their existing lenses will perform on a new camera, especially on one with a higher resolution sensor. An FF, 36 MP sensor corresponds to 104 LP/mm and a 50 MP sensor corresponds to 144 LP/mm. Testing done with 10 and 30 LP/mm charts are therefore meaningless when it comes to answering these questions.
As it is now, there is an large discrepancy between test results published by Lenscore and those published by DxO. If you believe Lenscore the Nikkor 600mm f/4 is 31% sharper than the Nikkor 85mm f/1.4. If you believe DxO the 85mm lens is 25% sharper than the 600mm, tested on a Nikon D800E.
The relatively new DxO definition of a lens resolution expressed in PMP (Perceptual Megapixel) is limited to its performance on a specific camera and not very useful in predicting the performance of that lens on a different camera.
The only way to know for sure would be if the industry started publishing charts showing the lens image contrast (readability) as a function of test chart line pair density (or test chart MP). Since newer, high resolution sensors correspond to 104 LP/mm (36MP) and 144 LP/mm (50MP), you would like to know how the lens performs at various test chart line pair densities (or test chart MP) up to 144 LP/mm (50 MP). This way you could clearly see at what resolution (in LP/MM or MP) your lens stops producing readable results compared to the resolution potential of your image sensor.
This information would end the arguments between the optimists who think that their existing lenses will give them 45 PMP images from their new 50 MP camera, and the pessimists who think that their new high resolution camera will need all new lenses.
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