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Photo Technical

Size counts in focal length; bigger and more is best – A48

Welcome aboard photo enthusiasts… On we go to the tenth edition clarifying the list of camera specifications.  The (randomly chosen) Lumix DMC-FX150 camera, manufactured by Panasonic, viewable with many other fine cameras on such websites as dpreview.com will serve as our sample. The last article was completely devoted to discussing Shutter priority. It, in addition to Aperture priority, are certainly the essential in understanding the fundamentals of photography.  Now we move on to:

Focal length multiplier: – This is somewhat more complicated to explain, and I have been considering how long this terminology will be of value to photography in our changes to the digital world, but I’m not sure of the answer.  Therefore I will do my best to clarify what it means, and in doing so the attached photo with this article will prove helpful.

The left side of the photo shows a seagull against a clear blue sky taken on 35mm (size) film or digital image sensor.

The right side shows the same seagull image, but notice it shows less of the blue sky…it has much of it cropped out.

This right side sets the example that most digital cameras, certainly all the pocket point and shoot cameras do not have a full (35mm) size image sensor.  They are smaller as is shown on the right side.

When their size is mentioned you will see such fractions as 1/3 or 1/1.8 or 2/3, and there are more, but they all are in comparison to 35mm and they all are smaller in size by comparison.

As in other aspects of our lives, size is important.  We here about megapixels all the time, knowing the more the better, and a larger image sensor can hold more pixels.  Then it is wise to realize that having more in not better than having more and bigger pixels. Therefore, a 6 megapixel with a 2/3 sensor is better than a 6 megapixel camera with a 1/3 sensor, because the 2/3 one is larger.

The fact that a sensor is larger, having more pixels and possibly larger pixels also has it producing less unwanted noise artifacts, and gives it a better dynamic range.  The latter meaning the ability to successfully capture detail in both the shadow and highlight areas of a scene to be photographed.

Looking into the meaning focal length multiplier can go into this type of information and considerations, but there is more and it concerns optics and our lenses.  This is signified when you see “FLM is 1.5X.”

In the example photograph, let’s say in the full 35mm the seagull on the right was photographed with a 200mm lens.  The same image on the right shows a cropped “by the size of the sensor” version if taken with a pocket camera having a smaller chip.  What it is in actuality showing you is the image equivalent as if it were photographed with a 300mm lens.  And this is what is meant with the FLM 1.5 X 200 = 300mm

Nearly all digital cameras, excluding more expensive digital SLR’s with full size 35mm image sensors, have smaller chips and some conversion factor.  If you are unable to change lenses on your camera, it’s really not necessarily relevant, except for giving you a better understanding of your camera.

If you can change lenses, you would multiply the FLM with whatever lens you were using to get the actual (new) zoom range.  If you had a 70-210mm zoom, with a FLM of 1.4X it would become a 98-294mm.

In this way, this is very nice.  Lenses with greater zoom ranges are heavier and more expensive (if maintaining the equal quality), and this conversion is therefore working for you.  On the wide angle side it is not though.  A more expensive extra (super or ultra) wide 17mm wide angle will now, with a FLM 1.4X, be a 24mm.

What can we expect; there is a yin and yang to everything.  Smaller chip has a better FLM conversion to capture a smaller ship at a distance, but this will make it difficult to get those full cabin shots…

Lens thread: No – Lenses with thread would enable you to add on attachments, such as filters, hoods and modifiers.  Throughout my career I never was a filter nut, but there are filters such as a polarizer, ND filter, color conversion and color correction filters; some can be handy, and others that today are not necessary.  A future article will revisit filters. 

Lens hoods can also be attached by the lens thread.  They help shade stray light from entering the lens if, for instance, you are shooting towards the direction of the sun.

Modifiers for a lens would be an additional lens you could thread on to, for instance, makes it a wider lens.  In other word, it could transform the FLM 1.4X 17mm that became a 24mm back to a 17mm again, that is, if you had lens thread.  It’s not the optimum optical solution, yet better than no solution to get those full cabin shots, with which I leave to ask for permission to come ashore.