Skärpa

[Khalad]

Lysande! Väsentligt bättre, kanske t o m lite överskärpt! ;-)

Skärpningen i LR är ju precis likadan som i ACR, så inte behöver du överge LR pga skärpningen. Här är ett förslag du kan testa på landskapsbilder som ska publiceras på webben:

I LR eller ACR, efter vitbalansering och exponeringsjusteringar, sätt Clarity=24 och Vibrance=12. Sätt skärpningen på Amount=60, Radius=0,7, Detail=70 och Mask=20 som utgångsvärden.

Studera bilden i 100%, ser det inte bra ut får du justera A=50-70, R=0,6-0,9, D=50-70, men håll masken konstant=20. Det ska se överskärpt ut i detta läge. Ta bort all brusreducering, även color som står på 25 som default. Sätt till noll. (En bild tagen på ISO 100-200 alltså.)

Exportera din bild från LR eller öppna från ACR i 16 bitar i full storlek till PS och välj utskriftsskärpning för Screen, Amount=High.

I PS, skala ner bilden till t ex 2500 pixlar på långa sidan med Bicubic. Inte Bicubic Sharper.

Skärp nu den nerskalade bilden en gång till med PS:s Smart Sharpen, Basic läge, Amount=70, Radius=0,3, Remove=Gaussian Blur och klicka i More Accurate.

Jämför med att "bara" exportera en bild från LR! Olika kameror och objektiv är olika skarpa, så vissa kameraspecifika justeringar krävs.

Tänkte prova dina förslag men är inte säker på att jag förstår. När du säger exportera bilden från LR, menar du väl exportera den med de inställningar jag nyss gjort (och som du föreslagit) och då måste jag välja ett annat format än RAW, väl, tex TIFF eller jpeg. Dom är ju båda komprimerade, vad väljer jag? Trodde inte det var så lyckat att bildbehandla komprimerade bilder i PS, även om det såklart går? / Björn T

 

[Rommel]

Tänkte prova dina förslag men är inte säker på att jag förstår. När du säger exportera bilden från LR, menar du väl exportera den med de inställningar jag nyss gjort (och som du föreslagit) och då måste jag välja ett annat format än RAW, väl, tex TIFF eller jpeg. Dom är ju båda komprimerade, vad väljer jag? Trodde inte det var så lyckat att bildbehandla komprimerade bilder i PS, även om det såklart går? / Björn T

TIFF är inte förlustkomprimerande. Det är TIFF du ska välja om inte PS kan öppna RAW-filerna direkt vilket är det bästa.

/Stefan

 

[Rommel]

Det är konstigt att vissa inte kan få till det med skärpan genom att använda enbart Lightroom eller plugin.
Det är ytterst sällan jag "måste" ta in det i PS för att skärpa upp. Oftast handlar det då om om lokal kontrastökning.
Men LR finns 3 verktyg för skärpning. Den som finns som flik i Develop modulen, en som man kan pensla på, samt vid export.
Kontrast och Clarity kan sedan också användas för att få en känsla om mer skärpa.

/stefan

 

[alfin]

Tänkte prova dina förslag men är inte säker på att jag förstår. När du säger exportera bilden från LR, menar du väl exportera den med de inställningar jag nyss gjort (och som du föreslagit) och då måste jag välja ett annat format än RAW, väl, tex TIFF eller jpeg. Dom är ju båda komprimerade, vad väljer jag? Trodde inte det var så lyckat att bildbehandla komprimerade bilder i PS, även om det såklart går? / Björn T

Exportera en okomprimerad TIFF-fil i 16-bitars Prophoto RGB i full storlek från LR med de inställningar jag gav dig ovan och klicka i längst ner i exportfunktionen att den ska öppnas upp i Photoshop.

Skala ner bilden i PS med bicubic till 2400-1200 pixlar och lägg på Smart Sharpen 70% och 0,3 px. Jämför före och efter, så ser du skillnaden mellan att bara göra det i LR och att skärpa upp den nedskalade bilden en gång till i PS.

Vill du spara till jpeg för webb, så konvertera först Prophoto till sRGB och sedan från 16 till 8 bitar innan du sparar.

 

[Martin Chab]

There is not a single reason for why a landscape will be less sharper than a studio portrait, but a combination of several factors.
Probably the most important is related to de MTF (modulation transfer function) of the lens. A very fancy title for a very simple to understand phenomena: no lens reproduces the same contrast in both sides.
Let me clarify: lets put a page which is half pure white and half pure black. Even if we could consider that piece of paper as having a 100% contrast, the image produced in the other side of the lens will never have 100% contras but a lower number. The reasons are several but just consider the dispersion of the glass. But the interesting thing here is that the contrast continues to go down as the frequency is higher. Putting in another words, if you take a picture with black and white stripes getting thinner and thinner and closer together (the frequency of the stripes going higher) you will see clearly that the contrast of the stripes will diminish as the lines get thinner and closer to each other. Up to the point where you can not distinguish any line (the lines becomes a continue tone of grey), that point is called the resolving power of the lens (there are diverse definitions depending on the author but that´s not important to understand the effect, it is just a matter of where you consider the resolving power point).
It is clear now that a landscape will have less contrast for the fact that the frequency of the image is higher.
And believe it or not contrast is the same as focus. Think in this way: a black dot perfectly focused will produce the same dot on the focusing plane and the contrast will be the maximum possible, but, an out of focus lens will "disperse" that dot over a larger area and, thus, reducing its contrast.
Actually any value under 50% MTF is considered to start to be out of focus.
Viewed in this way focus=contrast.
Don't believe me? try this simple exercise: take any picture and put up the contrast with any mean you like (for example an S shape cubes) and you will see how much sharper it looks.
Add to this the fact that all the cameras has a flavour of OLPF (optical low pass filter) that is nothing but a blur filter (it doesn't allow the high frequencies to pass though to avoid moiree) reducing even more the contrast (focus).
That also means that an image taken in a studio with flash, having a higher contrast, will be viewed as sharper.
In the other hand a landscape will always cast light in many directions and many of the rays that are not part of the image will reach the lens (even if using the attached shader on the lens) reducing even more the contrast (that light will "invade" the rest of the image).
Add to this the UV an infrared light that is much higher in a landscape that in a studio situation. Our eyes doesn't see it but the camera sees some of them.
Also consider that most of the lenses has a lower ability to resolve images at it ends (closest and furthest focus positions) and most of the landscapes are taken at infinite.
There is also the Kell factor (related to frequency and sampling of the sensor). If of any interest i can do a simple explanation on this factor.
As a final thought, the sharpness is a very complex function on how the brain processes the image. For example a healthy dose of grain will enhance the perception of sharpness (that's why a picture taken with film looks often sharper than a digital one). Colors also produces an illusion of contrast. In a landscape is very difficult to have any control on the color contrast of the scene.
The subject is huge!!

 

[Khalad]

There is not a single reason for why a landscape will be less sharper than a studio portrait, but a combination of several factors.
Probably the most important is related to de MTF (modulation transfer function) of the lens. A very fancy title for a very simple to understand phenomena: no lens reproduces the same contrast in both sides.
Let me clarify: lets put a page which is half pure white and half pure black. Even if we could consider that piece of paper as having a 100% contrast, the image produced in the other side of the lens will never have 100% contras but a lower number. The reasons are several but just consider the dispersion of the glass. But the interesting thing here is that the contrast continues to go down as the frequency is higher. Putting in another words, if you take a picture with black and white stripes getting thinner and thinner and closer together (the frequency of the stripes going higher) you will see clearly that the contrast of the stripes will diminish as the lines get thinner and closer to each other. Up to the point where you can not distinguish any line (the lines becomes a continue tone of grey), that point is called the resolving power of the lens (there are diverse definitions depending on the author but that´s not important to understand the effect, it is just a matter of where you consider the resolving power point).
It is clear now that a landscape will have less contrast for the fact that the frequency of the image is higher.
And believe it or not contrast is the same as focus. Think in this way: a black dot perfectly focused will produce the same dot on the focusing plane and the contrast will be the maximum possible, but, an out of focus lens will "disperse" that dot over a larger area and, thus, reducing its contrast.
Actually any value under 50% MTF is considered to start to be out of focus.
Viewed in this way focus=contrast.
Don't believe me? try this simple exercise: take any picture and put up the contrast with any mean you like (for example an S shape cubes) and you will see how much sharper it looks.
Add to this the fact that all the cameras has a flavour of OLPF (optical low pass filter) that is nothing but a blur filter (it doesn't allow the high frequencies to pass though to avoid moiree) reducing even more the contrast (focus).
That also means that an image taken in a studio with flash, having a higher contrast, will be viewed as sharper.
In the other hand a landscape will always cast light in many directions and many of the rays that are not part of the image will reach the lens (even if using the attached shader on the lens) reducing even more the contrast (that light will "invade" the rest of the image).
Add to this the UV an infrared light that is much higher in a landscape that in a studio situation. Our eyes doesn't see it but the camera sees some of them.
Also consider that most of the lenses has a lower ability to resolve images at it ends (closest and furthest focus positions) and most of the landscapes are taken at infinite.
There is also the Kell factor (related to frequency and sampling of the sensor). If of any interest i can do a simple explanation on this factor.
As a final thought, the sharpness is a very complex function on how the brain processes the image. For example a healthy dose of grain will enhance the perception of sharpness (that's why a picture taken with film looks often sharper than a digital one). Colors also produces an illusion of contrast. In a landscape is very difficult to have any control on the color contrast of the scene.
The subject is huge!!

Thanks a lot, very interesting to read your summary on sharpness in landscape pictures. Although I have not spent lots of time to think about what you say, I manage to follow most of it (I have studied advanced physics). For me it certainly is a bit extra interesting as you do point out that both of the factors I brought up in answers as suspected reasons to difficulties with perfect sharpness in landscape pictures - the high frequency of these pictures and the Moiré filter effects - according to you actually are of importance, although there are still more reasons.
Now, I am very curious if you can make a similar summary on how to treat these high frequency landscape pictures so they look like Perfectly Sharp Pictures taken by some gross format cameras!

Many thanks again
regards/ Björn T

 

[Martin Chab]

Mmmm. There is no simple answer for that because all the elements that i mentioned are physical limitations.
A better lens of course will helpl (a higher MTF lens).
Some cameras truly benefit from removing the low pass filter, but you will loose the guarrantee, the camera will suffer more from moiree, the white balance will be trickier and you will harm the autofocus in the models that has no micro adjustement.
A good UV always help but a hot mirror will help even more.
A matte box will help a lot but is expensive (who knows why) and big and cumbersome.