Tag Archives: digital negative

Testing with high/auto ISO settings

I recently attended a local gathering for wedding-related vendors in the newly renovated ballroom at the American Legion (on Bull St, in Savannah.) I set the Nikon D7000 to shutter priority with Auto-ISO enabled (max at ISO 6400.) During editing I created three variations from the original color image so the set contains:

  1. original (color)
  2. B&W conversion
  3. Color fade
  4. Color fade + toning

This was a ‘mixed lighting’ environment (late afternoon daylight + incandescent lights) so I selected the Lightroom default for ‘incandescent’ white balance.

In general, the originals were ‘noisy’ so I applied some ‘noise reduction’ using Adobe Photoshop Lightroom.  IMO, the B&W images look the ‘best’ with the original color version be acceptable with the exception of the first image (captured at ISO  400 and several stops under-exposed so the tinkering introduced quite a bit of ‘noise’.) The ‘toned’ images present a different ‘look’, especially for the venue. BTW – Jeff Brown (All About You DJs) was manning the sound station.

A PDF slide show includes EXIF information.

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.)

Histograms

  • 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)