Archive for the ‘Digital Photography’ Category

Lens profiles for ACR and Lightroom 3

Monday, July 26th, 2010

checkerboard

Adobe Labs released Lens Profile Creator utility that enables creation of custom lens profiles for Photoshop CS5 (ACR 6.1) and Lightroom 3.

This page contains profiles for some Zeiss ZE lenses for Canon EOS 5D II that I created using that tool. The profiles are free to use.

Currently there are profiles for the following lenses:

  • Distagon 21mm ZE
  • Distagon 28mm ZE
  • Makro-Planar 50mm ZE
  • Makro-Planar 100mm ZE

Click here to download

Examples

Chromatic aberration

Extreme corner shot with the 28/2, uncorrected.

28-2-unc

Extreme corner shot with the 28/2, corrected with ACR 6.1

28-2-cor

Distortion and vignetting

Distagon 21mm, uncorrected (click the image for larger picture)

D21-unc

Distagon 21mm, corrected in ACR 6.1. Exact same settings, but lens correction on.

D21-cor

Distagon 21 – distortion correction

distortion

Update Aug 22, 2010

Locations for the profile files

For Windows Vista or Windows 7

C:\Users\(User Name)\AppData\Roaming\Adobe\CameraRaw\LensProfiles\1.0
C:\ProgramData\Adobe\CameraRaw\LensProfiles\1.0

For Mac

/Users/(User Name)/Library/Application Support/Adobe/CameraRaw/LensProfiles/1.0
/Library/Application Support/Adobe/CameraRaw/LensProfiles/1.0



Sharpening and Micro Contrast

Saturday, May 8th, 2010

Sharpening and micro contrast enhancement has been frequently used in film photography. This article briefly introduces similar digital and analog techniques.

Digital Unsharp Mask

Unsharp mask selectively increases contrast of edges and small objects by making dark areas of edges darker and light areas of edges lighter. Since this creates a sharpening effect, unsharp mask is frequently used to improve apparent sharpness in digital imaging. The following image shows enlarged detail of an edge with and without unsharp mask. The image consists of two gray boxes; the upper part is with USM applied.

Unsharp mask - edge detail

If USM is used with narrower radius settings, it can effectively increase apparent sharpness. The following image shows effect of the unsharp mask on an image. The first character R is normal, the second is a copy of the first one with gaussian blur applied and the third one is a copy of the blurred one with unsharp mask applied.

Unsharp mask - sharpening effect

If USM is used with wider radius settings, it can increase micro contrast.

Eberhard Effect

Exposed molecules of silver halides react during development with developing agent and convert the white silver halide into black silver and creates visible photographic image. This chemical reaction breaks up the developing agent and creates certain byproducts that are capable of retarding further chemical reaction – development. Eberhard found that if developer is left absolutely still, smaller details and edges are developed more rapidly than larger areas, because smaller areas and edges can be easily surrounded by fresh developer, while silver halide particles inside large areas are surrounded by exhausted developer that does not have the vigor of the fresh one. Eberhard effect can be observed in still developers and diluted developers, but exists in conventional development as well and is frequently used by photographers to increase micro contrast and apparent sharpness. The effect can be replicated by digital unsharp mask. An extreme detail boosting technique, which turns photograph into graphics is based on copying or enlarging the photographic image to a large format high contrast film and developing with emulsion soaked in developer pressed on a glass sheet so that there is only thin layer of developer that can’t move. The film is copied and developed this way several times. I applied USM  on black and white image in Photoshop four times to achieve visually identical effect:

detail-filtration

As you can see, tonality is gone and the image is created only by local contrast.

Micro Contrast in Lenses

Camera lenses also exhibit micro contrast – or lack thereof. Lenses with good micro contrast  have good MTF at frequencies around 10lp/mm. There is some consensus that Zeiss lenses consistently excel in micro contrast.

The following two images are taken at the same day and hour, identically processed, but with two different lenses. First was taken with Canon EF 35/1.4L and second with Zeiss Distagon 28/2 ZE. Both are sharp lenses, but one has bad micro contrast and one has good. Click on the images to see larger version.

EF 35/1.4

Distagon 28/2 ZE

Useful links:

http://www.luminous-landscape.com/tutorials/understanding-series/lens-contrast.shtml

http://www.zeiss.com/C12567A8003B8B6F/EmbedTitelIntern/CLN_30_MTF_en/$File/CLN_MTF_Kurven_EN.pdf



Canon EOS 5D Mk II Noise

Saturday, January 31st, 2009

Problem

There has been some discussion about noise level of underexposed shadows from Canon EOS 5D MkII at ISO 100 compared to other FF cameras. I usually don’t have to push the exposure and find the problem theoretical, but I found the issue intriguing and did some tests.

  • I do not think it is a good idea to underexpose like that, I am merely looking at the behavior of the camera or the raw converter
  • The noisy samples are 100% crops from 21MP sensor and I the impact on actual prints will be minimal
  • It is possible that Canon or Adobe will be able to mitigate the problem in next update of Canon firmware or ACR update

Samples

Image straight out of the camera with default ACR settings, no corrections applied.

 

Here is the actual ACR settings from the Basic tab. In addition to that, I tweaked the Luminosity and Color Noise sliders so that the noise is minimized, but not so much as to introduce the compact camera look. I use custom camera profile based on the GMB checker. I also tried the canned Adobe profiles as well, they produce different levels of noise, some are higher than the examples here and some are lower.

settings

 

100% crop from the above image. The image has been pushed by 1.5 EV. Given the heavy exposure correction, it looks decent to me.

 

Another 100% crop from the above image. The image has been pushed by 1.5EV. It is possible to tweak the curves and noise slider so that there is no noise on the roof or in the sky, but other areas of the image then start looking like a compact camera picture with removed noise.

 

Another 100% crop from the above image. Again, pushed by 1.5EV.  If more noise removal is performed, the rendering of the branches and edges looks like a compact camera shot.



Film vs. Digital

Sunday, May 11th, 2008

Many articles and posts on the Internet claim or disprove advantage of small and medium film format over digital. The two media are very different and it is not completely fair to look at digital with having film as an etalon of the best achievable quality. Here is in a nutshell what I have learned in my almost three decades of film photography and several years of work with DSLR.

 

Digital gives more faithful reproduction of reality

Some color films are optimized for portraits, some are good for landscape and all have some characteristic presentation. Digital cameras don’t do that. Owner of the GMB Color Checker can see that in a simple test. With a calibrated camera, the colors from the digital system will be spot on, but on film some patches will be noticeably off, no matter how good is the process.

Images from digital cameras are easier to post-process

This allows more flexibility with digital images. Compared to film, digital files straight out of the camera can be flat looking, but they can be easily manipulated without any damage to the data. From one shot one can create Velvia looking picture as well as Portra looking one. Processing actual Velvia shots into good portraits is not an easy task.

Digital photography should be compared with color film photography and not B&W film photography

Some photographers like to argue that digital printing does not allow to create that "Baryta look". Some people say this is not true anymore, but  my point is that you should only compare digital with color film.

Resolution on digital cameras works differently than film

With film, the quality of the print slowly deteriorates with enlargement. The best print quality is achieved with contact print. The bigger the enlargement, the lesser the detail and sharpness. To the contrary, with very high quality lens, quality of digital print does not exhibit any deterioration with enlargement as long as the original image has enough pixels to print at around 300 dpi. The digital image will however start breaking up when the size reaches the limit when there is not enough pixels to print at 300 dpi. When the photographer starts "upsampling" the image, the quality goes down rapidly.

As a result, when  we compare a 300 dpi print from digital camera with medium film print (where the 300 dots per inch come from the camera and not from upsampling), the level of detail and sharpness will look very similar, but if we compare 20x enlargement from film with digital print of the same size, the film will look more detailed and more natural. This is apparently the main reason for disagreements whether film is better than digital or not.



Sharpening and Micro Contrast

Saturday, May 10th, 2008

Sharpening and micro contrast enhancement has been frequently used in film photography. This article briefly introduces comparable digital and analog techniques.

Digital Unsharp Mask

Unsharp mask selectively increases contrast of edges and small objects by making dark areas of edges darker and light areas of edges lighter. Since this creates a sharpening effect, unsharp mask is frequently used to improve apparent sharpness in digital imaging. The following image shows enlarged detail of an edge with and without unsharp mask. The image consists of two gray boxes; the upper part is with USM applied.

Unsharp mask - edge detail

If USM is used with narrower radius settings, it can effectively increase apparent sharpness. The following image shows effect of the unsharp mask on an image. The first character R is normal, the second is a copy of the first one with gaussian blur applied and the third one is a copy of the blurred one with unsharp mask applied.

Unsharp mask - sharpening effect

If USM is used with narrower radius settings, it can be used to increase micro contrast.

Eberhard Effect

Exposed molecules of silver halides react during development with developing agent and convert the white silver halide into black silver and creates visible photographic image. This chemical reaction breaks up the developing agent and creates certain byproducts that are capable of retarding further chemical reaction – development. Eberhard found that if developer is left absolutely still, smaller details and edges are developed more rapidly than larger areas, because smaller areas and edges can be easily surrounded by fresh developer, while silver halide particles inside large areas are surrounded by exhausted developer that does not have the vigor of the fresh one. Eberhard effect can be observed in still developers and diluted developers, but exists in conventional development as well and is frequently used by photographers to increase micro contrast and apparent sharpness.