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Digital Exposures – File Type Considerations & WB tools

Deciding on which in-camera file type to save is usually based on your needs and digital image file knowledge.  In a nutshell, RAW files provide more data and provide more options for editing.  If you are working a tough lighting situation then RAW probably a better choice.

Well, what about normal or good lighting scenarios?

  • If you need speed then JPEG is *usually* better (it will take less time for your camera to store a JPEG file than a RAW file – this is simply math – RAW files are usually several times larger than corresponding JPEG files; writing less data to a memory card *should* take less time…  A scenario (today, anyway) where JPEG makes sense might be any sport activity with rapid action – you don’t want to be waiting for your camera to save the last image to take that next picture…
  • Otherwise, I suggest staying with RAW
  • For some cameras you can save both RAW & JPEG (or perhaps other image file formats like TIFF.)  This can be useful if you need both lattitude in development (i.e. from selected RAW images) and faster processing (i.e. from JPEG files; smaller file ~= less time to process for output/delivery.)  Note that this setting consumes storage space RAPIDLY…

Editing your images – some guideline/suggested limits

Ok, you are now back at your computer and making your selects.  Let’s say that you have at least a few images where the exposure was not perfect and you need to make adjustments – how far can you go before your changes start impacting image quality?  It depends on several variables but for this discussion we will assume that you camera is set to the highest quality image that it can produce.  In general, for exposure changes we can adjust:

JPEG  – exposure latitude = < 1 stop

  • suggest edit limit of 1/3 stop over OR
  • 1/2 stop under exposure

RAW – exposure latitude =  6-8 stops (could be more – depends on image sensor)

  • suggest edit limit of 1 stop over/under

Note that you can surely make larger changes than those suggested above – the point is that you want to get your capture to be within easily editable ranges.  So, how can you get your exposure as close to possible to ideal? I suggest:

  • taking test pictures and evaluating the histograms (See below) AND/OR
  • consider using the bracketing features of your camera (auto-bracketing is a feature where your camera will capture multiple images and vary the exposures based on how you configure the bracketing option.)


  • scene dependant brightness levels and quantity of pixels in an image
  • histograms from RAW files actually display, interpolated JPEG data
  • 0  = black, dark side (usually on the left, i.e. dark areas with shadows)
  • 255 = brightest, white side (usually on the right,  i.e. the sky)
  • a ‘balanced’ histogram is ‘well exposed’
  • too light (high values on the right) = contains some under-exposed areas
  • too dark (high values on the left) = contains some over-exposed areas
  • clipping occurs when ‘detail’ is lost (values on the extreme left or extreme right of the histogram)

Use Calibration TARGET Reference Cards

Expose for your SUBJECT (center of histogram)

  • single source reference – simple histogram
  • multi source reference – i.e. three stripes, white, black gray; where are your high & low key light areas

Using a target

  • take picture (with subject holding target or target in scene); fill with target
  • evaluate histogram – adjust exposure if histogram leans left or right (i.e. keep Aperture but adjust shutter speed up or down)

The Camera Never Lies?

Which Statement is True?

A Camera Never Lies… or

A Print is only one possible interpretation of an image…

Both have merit and both have depend upon human and medium variables.  In the old (film) days there (very broadly speaking) were two types of photographers:

  1. those who created photos and hired out developing and printing and
  2. those that handled print creation from start to finish.

The basic limits of what could be done with a print were tied to the  quality of the original negative image;  the printing process allowed for an additional creative touch to be applied to the final print.  Those photographers who handled all of these steps could of course have maximum creative input into the final output.   It should be noted that most (if not all) aspects of image creation and printing were controlled by the photographer or printer.  The choice of film brand, type, ISO as well as the choice of chemicals and papers used all affect the final outcome and, in  many cases become a type of signature for a photographer or printer.

In the digital photo world these factors are still in play (or they can be.)  Camera manufactures have made tremendous, perhaps even miraculous progress in developing current digital cameras (entry level to pro dSLR systems.)  Photo-printer manufactures have made similar levels of improvements.  It is now possible to click the shutter button, wait a few seconds for the image to pass through the air to your wireless network, reach your computer and then be shuttled to your inkjet printer – all  without you having/needing to decide on any camera settings, computer settings, printer settings, nada!   Provided that your ink levels are good and your photo-printer paper is of reasonable quality you will most likely wind up with a print that is acceptable and it may even be a photo that your share with others.

If you take the ‘no-hands’ approach described above then for each auto setting you use you are actually allowing the camera (i.e. the knowledge/wisdom/skill of the camera, printer, computer & software engineers) to pick for you.  There is nothing wrong with this – it’s just a choice that you make; most serious photographers (pro and non-pro) will make these choices (i.e. they won’t use any automatic settings.)  Does this really make any difference?  So far, no, not much difference – well, not until you start doing truly creative things with the image/print.

Cameras (film or digital) are really, really, really dumb – compared to the combination of the human eye and brain.  The camera will never ‘see’ the level of image complexity that we perceive in a scene (our eye/brain combination is a 3d view; a camera only has a 1d, flat view.)   So, a camera never lies really means that a camera never sees the whole truth…  How about:  the print never lies? The camera is much closer to the original image – any print that we encounter is in fact, one interpretation of any given image and as such, is much less likely to be close to any sort of truth – a digital negative (file) is much closer to the truth (errr, the camera’s truth.)

JPEG, TIFF, RAW – the Digital Negative

Camera manufactures offer you choices – most cameras include an option for RAW files.  The choice of digital negative file type impacts image quality and places practical limits on what can be done with your negative.  JPEG  files are cooked – i.e. they are sort of like using other automatic settings – they limit your creative input control.  RAW files allow the most flexibility for post-processing.  A simple example is the choice of light temperature (i.e. setting the camera for daylight, night, cloudy, etc.)

If you have a RAW file then you can change this after the photo has been taken; if you use a JPEG file then you have to re-process the file (i.e. create a new file to use) to fix a problem like this.  Since a RAW file is never a work-file, you could argue that there is no difference.  In addition, the latest version of Adobe Lightroom treats all negative files as if they were RAW files (any changes result in the creation of a new file so the original is never changed.)  If your camera supports it I suggest that you try using a setting that provides you with both a RAW file and and a JPEG file – only then will you be able to see the differences in both types of capture.

NOTE – since I first wrote this many software products have changed – many current products allow you to treat a JPEG file like a RAW file, i.e. any changes are made to a copy of the original file so your ‘negative image‘ is preserved as long as you use software that does not change it…