Canon 5D Mark II Sharpening

[kapkin]

I always shooting RAW mode and picture style adjustment is always neutral.It means no sharpening adjustment,no contrast,no one.Because I always prefer to use this adjustments on the raw converter.But sometimes I am asking to my self, Is ıt right approach, especially capture sharpening? I mean maybe sharpening adjustment should be on camera and the other adjustments might be on raw converter.?Is there any discrepancy,on camera or on photoshop raw converter.?Thanks for answers.

[calexe]

The image parameters you have set on the camera will not affect the RAW file in any way. Some image processing programs, like DPP, will default on the image parameters set on the camera at the moment of shooting, but you can change these any time without affecting the RAW file. Setting these parameters in DPP to some values (the ones you want or the defaults at time of shooting) affect only the conversion to JPEG, which actually you must make at some moment. And, of course, the image displayed on the PC screen. But the RAW file remains untouched.

Further, the camera shows an "embedded" JPG image on your LCD. The image parameters you may set affect how the embedded JPEG is displayed on the LCD, but if you shoot RAW then nothing else than the image on the LCD. Knowing this you might play a little bit to choose the image parameters wisely. Here is what I do (will be a little bit surprising, you may judge if this is right for you):
- WB: leave on auto, you may adjust it at PP if needed
- Picture Style: Faithful or Neutral. Others, especially Landscape, may show false clipping alerts.
- Contrast: -4, minimum (!!!). High values may show false clipping alerts. You will restore Contrast to what is needed on PP.
- Color Tone, Saturation: you may leve them on middle values
- Sharpness: +7, maximum (!!!). This does not affect the RAW file. But it gives you the chance to better check in the LCD if your image is correctly focused. By the way, this is what the camera does in LV, when magnifying the image +5 / +10 in the LCD, even if they do not tell this explicitely. You will restore Sharpness to what is needed at PP.

Your LCD image may not look brilliant, but you can see better what is important: if you exposed adequately (checking histogram & clipping) and if your image is sharp.

[Colin Southern]

Hi Izmir,

Just to follow on a little from Cristian's excellent post ...

Normally a good rule is "anything you CAN do in ACR you SHOULD do in ACR", but personally, I make an exception to this rule for capture sharpening. For capture sharpening, Canon recommend 300% @ 0.3 pixel for 1D3 and 1Ds3 cameras (and so in theory, this should apply to any camera between about 8MP and 21MP) (ie all of them) ... and unfortunately, ACR only goes down to 0.5 pixel as a minimum sharpening radius (which probably souldn't be "bad" ... just not as "good" as 0.3).

[kapkin]

Cristian and Colin thanks both of you for your valuable informs.

[GW Greg]

What is "clipping"?

[Mark von Kanel]

Greg,

as far as i understand clipping refers to over exposure leading to high lights being blown and loss of detail in that area.

mark

[calexe]

Just as Mark said.
One more note: In the field you may see the "burned", overexposed zones clipping (blinking) on the LCD if you camera is set to do this. At home DPP / LR / etc. can also be configured to show overexposed zones on the image depicted on the PC screen. Sorry, perhaps my English is not the best one.

...
For capture sharpening, Canon recommend 300% @ 0.3 pixel for 1D3 and 1Ds3 cameras (and so in theory, this should apply to any camera between about 8MP and 21MP) (ie all of them) ... and unfortunately, ACR only goes down to 0.5 pixel as a minimum sharpening radius (which probably souldn't be "bad" ... just not as "good" as 0.3).

Colin, may I kindly ask you to put a link to that document from Canon explaining recommended sharpening? I feel I need to read more about sharpening and NR, would be useful for me (and maybe not only for me). Thanks.

[Colin Southern]

Colin, may I kindly ask you to put a link to that document from Canon explaining recommended sharpening? I feel I need to read more about sharpening and NR, would be useful for me (and maybe not only for me). Thanks.

Hi Cristian,

I have them as a bunch of PDFs (happy to eMail them to you if it helps), but one link regarding recommended capture sharpening can be found here (although in this on they recommend a USM of 250% @ 0.3, not 300% (which they document elsewhere). On a side note, you'll note that they also recommend a threshold of 1, but I prefer the result I get at 0 (for base ISO shots).

[Glenn NK]

What is "clipping"?

Greg:

This is a very good question that has a very difficult answer. I'll try my best and if I get something wrong, I trust others will correct it. It should also be on a separate thread as it doesn't relate to sharpening.

There are three channels in colour photography - Red, Green and Blue - the so-called RGB of colour photography.

Each channel can have values from zero (black) to 255. If the light being captured has a value of greater than 255 (the sun which is extremely bright), then one or more channels are said to be "clipped".

Any number of the three channels can be clipped - quite often (again in the case of the sun), all three channels will be clipped. However there are situations where only one or two channels will be clipped. An example I'm familiar with is flower photography. The light meter reads the reflected light coming from the flower, and adjusts the exposure to a "correct" level. But in the case of a red flower (for example), the Red channel is often clipped when the Blue and Green channels are not. It's quite simple - most of the light coming from the red flower is red - and the light meter is reading all three values and taking an average. The light meter can't tell what colour the flower is so it assumes the average exposure of three channels, and the red channel is blown or clipped.

When a channel is clipped (sometimes called "blown"), there is no detail at all in that channel. In the case of the red flower where the Red channel is clipped (a value exceeding 255), there is no detail at all in the red. There is plenty of nice red, but there are no details in the red areas. However a red flower may have other colours and they will not likely be clipped.

So quite often with clipping in only one channel, some detail can be salvaged during processing.

However if all three channels are blown/clipped, there will be nothing but pure white and no detail at all. In other words there is nothing to see but white space. This happens frequently with light reflecting off water. What we call the specular highlights (the sparkle on the wave tops) are areas that are clipped in three channels.

There is method to prevent this, but it is not perfect. Shooting RAW helps because more can be salvaged from a blown RAW file than can be salvaged from a blown JPEG file - however this is not the prevention, it's just a partial cure.

The prevention comes in taking a test shot, and viewing the three colours in the RGB Histogram on the LCD. Here one can tell which channel is clipped. There however is one small problem which prevents this from being a perfect solution: the RGB Histogram is actually a JPEG conversion that the camera does for the LCD display and this doesn't accurately reflect the RGB levels of a RAW file. The LCD display cannot project a RAW file image, so the camera converts it to a JPEG (even if you are shooting RAW only.

Fortunately, there is one trick we can use to help compensate for this: many experts recommend setting the Contrast value to minus 3 or minus 4 in the camera's settings. I use minus 4, but this does not prevent all clipping - on specular highlights for instance - they are just too bright. I won't get into the settings because this is camera specific.

Back to the LCD: If one looks at the RGB Histogram, one can see the three channels - if one of them seems "jammed" to the right side of the histogram, it's probably clipped. Another trick if the camera permits is to turn the "clipping indicator" ON. When viewing the image on the LCD, blown/clipped area will flash.

The method of prevention in the field is to use less exposure, either with a faster shutter speed or a smaller aperture (larger f/number). It's trial and error, but in the case of digital not costly - provided the subject can be shot again. But you must use the RGB Histogram - there is an exposure histogram, but this just shows the average of the three channels - generally not much use for single colour objects such as a red flower or green leaves. I only use the RGB histogram.

The other side of this "clipping coin" is that in order to obtain maximum detail in our images, we should expose as brightly as possible without clipping - a delicate balancing act to be sure.

I just took a shot of a bright tungsten light on my ceiling (typical frosted dome cover). The Red channel is definitely clipped, the Green channel appears to be clipped a bit, and the Blue channel is definitely not clipped. So with some careful post processing I might get some detail in the brightest area - but I wouldn't get any Red detail at all.

I'm now going to pass the torch to others more knowledgeable than I, and I hope this isn't overwhelming. If it is, keep in mind that a few years ago, I was overwhelmed too. Now I'm just numb. Or is that dumb? I get them mixed up.

Glenn

[Colin Southern]

Each channel can have values from zero (black) to 255. If the light being captured has a value of greater than 255 (the sun which is extremely bright), then one or more channels are said to be "clipped".

Hi Glenn,

Sorta / Kinda ...

The 0 to 255 thing is more to do with an 8-Bit representation of a red, green, or blue picture element on a monitor - most cameras these days are working on a 14 bit A/D conversion, which give us 0 -> 16383 levels.

[calexe]

Nice topic. Hope the beginners will not be overhelmed

Colin: The link you mentioned is not functioning. It seemes The Digital Picture has retracted it from their site. Could you e-mail it to me if you have it? My contact information is under my profile. Thanks.

...
The prevention comes in taking a test shot, and viewing the three colours in the RGB Histogram on the LCD. Here one can tell which channel is clipped. There however is one small problem which prevents this from being a perfect solution: the RGB Histogram is actually a JPEG conversion that the camera does for the LCD display and this doesn't accurately reflect the RGB levels of a RAW file. The LCD display cannot project a RAW file image, so the camera converts it to a JPEG (even if you are shooting RAW only.

Fortunately, there is one trick we can use to help compensate for this: many experts recommend setting the Contrast value to minus 3 or minus 4 in the camera's settings. I use minus 4, but this does not prevent all clipping - on specular highlights for instance - they are just too bright.
...
Glenn

Good input. Thanks.

I have a method to avoid the test shot(s) . That means one can know before shooting to select adequate exposure in order to avoid clipping. For the moment the method is described on my site only in Ro, I will try to translate it in En next days. Of course, some aspects from real life cannot be avoided - like specular highlights (usually may be ignored) and clipping of single channels when luminance is not clipping. But still, you can eliminate the test shot in most situations. Sometimes there is no time for a test shot. I will be back.

Indeed, -4 on Contrast minimizes false clipping alarms in the LCD. Even so there remains a tiny reserve in the RAW image, that means clipped zones may still have details. Higher values on contrast may induce the photographer in error and he might be tempted to reshoot with lower exposure, loosing detail and getting higher noise in the dark zones of the image. This is not critical with low ISO. But with high ISO (say +ISO 1600 on 7D) - then this becomes absolutely critical. This is the reason why some guys can shoot good image quality with ISO5000 on a camera like 7D. Probably with 5DII even at higher ISO (I could test only on my 7D).

For beginners, to better understand "clipping": Take a shot slightly overexposed, containing some burned zones. Then input the image in an photo processing program (like DPP) and drag the exposure slider to minimum. The image darkens dramatically. Only the burned zones remain white, because there is no detail there, no image information. These are the real "burned" zones.

[Colin Southern]

Colin: The link you mentioned is not functioning. It seemes The Digital Picture has retracted it from their site. Could you e-mail it to me if you have it? My contact information is under my profile. Thanks.

Hi Cristian,

The link is working for me -- it is a bit slow though (and it's a PDF, which makes it worse), but I've packaged up my Canon 1D3 / 1Ds3 PDF collection for you anyway ...

http://www.mediafire.com/?kcwnorr4g3yxkcf

[calexe]

Thanks. Got it.

[William W]

Thanks. Got it.

Me too, had a couple I did not have, thanks.

WW