Exposure Part 2

Exposure Part 2 - Making it work.

This week we look at more on making exposure work on a modern camera.  While early exposure based on the type of light worked, it wasn't really accurate enough, and the first light meters were the result.  At first the meter was a set of neutral density filters, and you would pick the proper filter, which gave your exposure.  This relied on the human eye, which is different person to person.  Then we saw the first electric meters, these were based on selenium, and operated as a type of photo-voltaic cell, it would when exposed to light produce a small voltage, the higher the voltage, the more light there was.  The result was a match-needle system, the voltage would be displayed and as you set the shutter speed or aperture, it moved another needle, when the two needles were matched, you had the correct exposure.   They were terrible in low light, and needed to be quite large, and ceased to be used in the 1960's when Cadmium Sulfide (CdS) based meters were developed.

These worked in a different way, by passing a voltage through the cell, as the light was higher or lower, the resistance was higher or lower.  These meters required a battery that would provide the same voltage from fresh until it suddenly dropped dead.  Mercury batteries had this characteristic and were cheap, until they were banned in the early 1990's.  Alkaline batteries which are cheaper and less toxic, tend to start at a higher voltage and gradually drop, requiring some form of voltage regulation circuit to provide a constant voltage to the cell.  Some meters still use CdS meters are still used, although other sensors are also used.  CdS cells could be quite small, and mounted inside the camera, giving a very good reflective light meter.

Manual mode, this one is for what you think the computer is likely to get fooled, for example when there is a lot of one tone, which isn't your primary subject, or your trying to do something creative.  A photographer by the name of Ansel Adams developed the zone system, for such circumstances.

Aperture Priority mode, when you want to control the aperture, and are not as concerned about the shutter speed.   For example your trying for a certain depth of field.

Shutter Priority mode, when you want to control the shutter speed, and are not as concerned about the aperture.  For example action shots.  Sometimes you will use it to freeze motion, and other times to emphasize it.  This can be very useful.

Program mode, your not really concerned about aperture or shutter speed, and just want an image.

Many modern DSLR Cameras also have "hint" modes, for example Sports or Portraits, these are similar to P mode, but will shift the values, based on the hint.  For example Sports mode, will attempt a high shutter speed to freeze action, Portraits mode will go for a higher aperture, to ensure a face is fully in focus.

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On my current regular camera, I use various modes, most commonly Av or Tv (shutter priority), there is the ability to shift the exposure by up to 3 stops,  so there is little need to use M mode anymore.  I also sometimes use the hint modes, I don't like P, but it is there....

This weeks image is from well back in the archive, it's a film image that was scanned, I don't remember from where, but I like the reflective nature of the image.  There are hundreds of these, that were scanned and never catalogued, and I am slowly getting them done. One thing I did do, was include some notes, in the exif data  and this one was originally shot on Agfa Vista 200 ASA Colour film, using the Konica FC-1 Camera.  

I think that's about all there is for this week

W.

Exposure Part 1

Exposure Part 1

Early Cameras were totally manual in nature, you had two things to set, how fast the shutter would operate, and how much light enters the lens.  Even the latest high tech DSLR that has more computing power than an IBM/360, as the ability to make these two settings.  The majority of people don't really think about this, they let the computer to all the thinking, but that can result in a poor image.

Shutter speeds are counted in seconds, fast shutters can exceed 1/2000th of a second, and many can be held open for long periods of time.   The amount of light is expressed as a fraction of the focal length of a lens.  A lens that is 100 mm long, at f/4 will have an opening that is 25mm in size, these fractions are based on a series of numbers, where each number allows double or half the amount of light, the lower the number, the larger the amount of light, these numbers are logarithmic in nature.  The typical values are 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32 although it's technically possible to go smaller then f/32 it would be quite rare, rare is another word for expensive.  In the 1970's and 1980's when 400 ISO (usually expressed as ASA in those days)  film was considered very fast, the standard lens was the 50mm, and most were between f/1.4 and f/2.  Current digital zooms, are quite a bit smaller, with f/4 to f/5.6 being common, then again with ISO values of 3200 and 6400 being common, this isn't a problem.    

Early cameras were all manual, and you would use rules like Sunny 16, to determine exposure.  Then light meters came out, which would measure the light, and provide values to the photographer.  Now, fast shutter speeds can stop motion, such as in sports, the smaller the aperture, the greater the depth of field (range of distance of image that is in focus), the larger the number, the smaller the depth of field.  With the same lens, the shorter the lens, the greater the depth of field, and the longer the lens focal length, the shallower the depth-of-field.   A short lens with a small aperture can have a nearly endless depth of field.

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You can creatively make use of this.  The image below has the ice on the rock in the foreground and the much lake also in focus, it was taken on a bright winter day, with a small aperture.  in this case the exposure was f/11 with a 22mm lens and a shutter speed of 1/200, with an ISO of 100.  I know this, because the original image was taken with a digital camera, that records this.   So the rock that is only 2 metres away and the lake horizon 1km away, are both in focus.  With other items you can use a larger aperture and a longer focal length to throw a messy background out of focus.

Some photographers will intentionally use a slow shutter speed to emphasize movement, this can give a really nice effect to moving water, giving it a dreamy quality.

I try to keep these postings fairly short, as long postings can get dull and boring, More on this next week in Part 2on exposure, when I will go into the mechanics of making it work with the modern camera.

That's all for this week
W

The editing process

So you go out shooting with your favourite camera, and come home with 500 images, now what? How do you decide what you will keep, and what will you throw away.

I almost never clear an image from the memory card, even if I know it's not going to be kept, for a couple of reasons,  when you started with 24 and 36 exposure film rolls, then 100 images "per roll" on a memory card is a lot.  After they are on the computer, I reformat the card.

The first edit I do, is a technical edit, if the image is poor, out of focus or wrong focus, the lighting or composition didn't work, then I toss the image.   I don't usually have time to play around with poor images, when I have dozens or hundreds of images to deal with.  The remainder get catalogued, and honestly, may of them will never see the light of day.   Others can sit in the archive for years, and then get pulled out for processing.   Then of course, we all have our favourites, this is one of mine.  I think before I stopped the blog before, I had this one posted.

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This weeks image is actually an old favourite of mine, it was taken on the first shoot with the Canon 300D (Digital Rebel) a camera that is now heading into semi-retirement.  My brother-in-law and I, were out driving around, and we saw this place, no signs for no-trespassing were about, and we took a few shots.  It is interesting how, a building sometimes will start to come apart.  This actually was a common design in the late 1800's.  It's called a storey and a half, a later modification was the storey and three-quarters where the side walls would be extended up further to give more head height.

As with most images, this was shot in colour, then processed to black and white through my normal mechanism.

I'll admit that this week is a little short, but I ended up writing this on Saturday afternoon, with a sore back that seems ready to give out.  I'll try for something more interesting next week

W

My workflow for digital images

My workflow for digital images.

I shoot everything in RAW mode, this is because JPEG, the normal output for most digital cameras, is a lossy format, it loses some of the image data that the algorithm, deems unimportant. If you normally, simply take your memory card to Walmart, and feed it into their machine for a bunch of prints, or your post everything on Facebook or Instagram, this is fine. If you like to do post processing of your images, then it’s not fine.  The reason for this is that it throws away a little more of the image each time, so after a few edits there is nothing really left.  Back in the days when disk space cost $1/MB and a 56K modem was considered blindingly fast; the need for high compression was worth the cost of lower quality.  Today when $100 buys a 2TB drive, and 10Mbit/second is considered slow, we don't need as high compression.  

I consider the RAW file, as the undeveloped film, I use RAW conversion software (UFRAW), as a standard developer which leaves me with a PNG file; essentially a transparency or slide, rather than a negative. I go through, and any that are obviously unable to be salvaged, get sent to the trash folder. Some that are iffy, I will go back to the original RAW file, and load it into the conversion software, and play with it, to see if I can get a better result. If the result is not usable, then it also gets moved to trash.

The rest are fed through a custom program that issues them catalogue numbers, and moves them to the archive. It’s still a work in progress and will eventually get rewritten to become more efficient and to work better, but currently it works well enough.  I want to eventually get it to do the raw conversion, as one thread then show the image in a second thread, so I can either accept or reject it, and then catalogue it, again in a third thread.  

When I am considering images for use, I go back through the archive and see if I can find what I want, these are then fed through another bit of custom software, that does a bunch of things, like re-sizing, conversion to black and white, toning, adding the copyright notice, etc. If something doesn’t work, I fix it, will it ever be ready for public consumption, probably not. The end of the process is a Jpeg file, either suitable for printing or for posting.

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If you think you need a fancy new Mac for this, you don’t, I use a 10 year old PC that runs Fedora Linux on it, I can load images into Gimp which will allow intermediate processing, but often use my own software so that I can get the same result each time.

This weeks image, Catalog Number E4700329, I like the angle on this one, it's unusual and the petals have a translucent effect on the front, because the sun was above and slightly to the right of the flower.  The background is actually leaves that are dark green, they turn black when converted to black and white.

I think that is all for this week, see you next.

W