Category Archives: How-To

True HDR explained and examples

I thought I’d spend the 2nd day of 2015 talking about “True HDR” versus “HDR effects”.

One is actually HDR, the other isn’t.

A bit of background. HDR is unique to digital photography, because back in the olden days (Pre-Bush Jr) most photography was done via a chemical process. Exposing film in a camera caused a reaction with light sensitive silver nitrate compounds, which were then dunked in various chemical baths to be “developed”. It was during this time/temperature process that the real magic of photography occurred. You never got to see the results until after this process, and I can vividly recall my palpitating heart the first time I opened a processing tank to view my first ever developed roll of Tri-X. Almost beat out by my first ever solo landing in a Cessna… Almost.

Film had a small range of contrast it could handle before it either made shadows go completely black or the highlights went complete white. This range depended on the film you were using. Slide film has the lowest (narrowest) contrast range; certain negative films the widest range.

With black and white negative film one could adjust exposure and then development to compress the image, also called “Zone System”. The Zone System is best remembered as “expose for shadows, process for highlights”

This was best used by photographers utilizing large format cameras, where a single frame could be processed differently from the other frames.

With digital, there is really no processing. So HDR was developed as a way to compensate for the limited exposure range of digital sensors. This is accomplished by making several exposures of a scene, bracketing each exposure to get images with good shadow detail then images with good highlight detail.

Using Photoshop or another piece of software, you then could stack the images and merge them into one single image with shadow and highlight detail. There are various effects that happen, and a good HDR image is almost like what the human eye can see.

Everything else is artistic intent.

HDR effects are simply taking a single, evenly exposed image and getting the HDR look by compressing highlights and shadows and causing edge effects. It’s not really, truly HDR. It’s just an effect.

That effect certainly can’t bring out details in shadows in a scene with extreme range.

Let’s take an extreme example. I uploaded to my gallery a scene of a piece of gnarled tree trunk with the sun backlighting the wood and pine needles. This one I did a 7-EV bracket to allow of the extreme brightness of the direct sun peeking through the pine needles.

Here’s a collage of the 7 exposure range I used….

All 7 exposures. (Click to Loupeify)

All 7 exposures. (Click to Loupeify)

Looking at the contact sheet, you can see where my trusty Nikon thought the proper exposure should be, exposure #4.  Wow…  It’s losing the shadows badly…  and the better single exposure is #5, or plus 1 EV.

And that’s where True HDR comes in.

Using only photoshop, I did a Merge to HDR pro, and played with the settings to achieve a very nice HDR of the scene.

Vola!  Click to gigantisize

Vola! Click to gigantisize

Next post I’ll examine several of the Android apps for HDR photography….

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Homemade Film Washer – How To

If you are into old-school photography and are shooting black and white, chances are you are processing your own film.

The final step in processing film is to remove all traces of chemicals using during processing. Modern films require much less washing than older films, but one still needs to remove all traces of the “fixer” or “hypo” during the wash. Without proper washing, that roll of film could be ruined by chemical stains later on, making it almost impossible to recover any images on it.

You can wash the film by running water into the developing tank, or use a drop-in film washer built for the purpose.

There are perhaps four types of film washers currently available, most run about 60 to 90 dollars mail-order.

Or you can make one yourself and save money.

The shopping list is small and can be found at any “big box” hardware store.

  • 4″ PVC pipe in a 2 foot length – $3.98
  • 4″ PVC closet pipe flange with knock-out plug – $6.77
  • 4″ PVC “test cap” – $0.83
  • 3/8 inch plastic tube fitting (I used one from a hose sprayer adapter from the grocery store), but these can be bought for about $1.00 or so.

Total out the store – about $12.54.

Optional is a jar of PVC cement. I omitted using this because the pipe fitted together quite well and this allows me to make changes to the design or for cleaning.

Start by cutting the PVC pipe to a length of 9 inches, with an optional cut of a ring of PVC material ¾” long (see photos). I used a compound miter saw to make the cuts, making sure the cuts were absolutely square and accurate. If you don’t have such a saw, borrow a friends or ask at the store for help in cutting, as 4″ PVC is quite thick and hard to cut by hand.

To make the simplest washer possible, you can simply attach the PVC pipe to the pipe flange, drill the 3/8″ hole, and attach the tube fitting and start using it. With this option, you will need a spare film reel at the bottom to avoid too much water pressure hitting the fragile film.

I decided to use the test cap to create a platform to rest the film reels on and create turbulence in the water flow. To do this, I used a ¾” piece of the pipe, placed this into the bottom of the flange then drilled a 3/8″ hole for the plastic tube fitting. Then I drilled several large holes into the test cap, and placed it into the remaining 9 inch piece of PVC to form the bottom film reel platform.

Then it was a matter of connecting the wash hose to the new washer and running a test. A small amount of water leaked from the bottom, as I did not glue anything together. This leaking is OK as “Fixer” is a bit heavier than water and this helps the washing process.

To test, I used a drop of red dye in the water, placed 4 film reels into the washer and ran the water at a small rate. The time it took to completely clear the red dye was 6 minutes. Combined with lifting the reels and agitating the water, this wash time could be cut to 4 minutes or less.

I originally built a washer in the mid-1980s, but after several moves this piece of equipment was lost. I researched buying a commercial washer and even on online auction sites, they’re still more expensive the buy than to make.

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