Challenging Old Rules - Linear and Circular Polarising Filters

When we start learning about photography we pick up allsorts of hints, tips and accepted rules about photography and photographic science.

One of these "rules" surrounds the use of polarising filters with cameras. It is recommended to always use the Circular Polarising filter because of the nature in which it works and doesn't affect the automatic focus and metering systems of DSLR cameras. When using a Linear Polarising Filter focus and metering can be affected by the way in which the filter affects light being reflected from the 45 degree mirror in these cameras.

But what about the Mirror less and Bridge camera are they affected in the same way and is there a compelling reason to use Linear filters in these cameras.








Here's an image of a reflection in a window.

The FZ330 is fitted with a Circular Polarising filter set for minimum cut.








Here's the same image with the filter rotated to give maximum cut









The same shot taken with a Linear Polarising filter at minimum cut








Here's the same shot with the filter turned to give maximum cut.

So photographically there is very little difference between the shots at maximum cut with either filter - or is there?


Well because the circular polarising filter is constructed with a linear polarising filter plus another circular polarising filter (1/4 wave plate) bonded to it, it has a higher light transmission loss than just the linear polarising filter.

Take a look at the some other exposures. With the circular polarising filter 1/6 sec and the Linear polarising filter 1/10 sec and 1/15 sec without any filter. So with the circular polarising filter we lose one and a third f-stops of light versus two thirds loss with the linear polarising filter.


This might not sound a lot but a difference of 2/3 rds of a stop is significant with the light gathering needs of cameras like the FZ200/300/330 with small sensors.

We need the maximum amount of light gathered by these sensors in order to get good images which are not ruined by noise in the image.


So is there a loss of focus and metering accuracy when using a linear polarising filter - well I did 5 exposures using single point AF method without the filter and then repeated it with the filter and there was no difference in focus point. Rotating the filter did not affect the exposure reading so it is apparent that with both the bridge camera and the mirror less CSC (I used the OMD -EM1 mk2 for the test) that there is no loss of accuracy.

So with the linear filters being cheaper and pass more light into the camera it is time to write the rule books again in my opinion for CSC and Bridge camera users.

Why Digital Cameras and Smartphones Save Images to the DCIM Folder

Every camera — whether it’s a dedicated digital camera or the camera app on your Android or iPhone — places the images you take in the DCIM folder. DCIM stands for “Digital Camera Images.”

The DCIM folder, and its layout, come from DCF which is a standard created back in 2003. 
DCF, or “Design rule for Camera File system” is a specification created by JEITA, the Japan Electronics and Information Technology Industries Association.

DCF is so valuable because it provides a standard layout. The DCF specification lists many different requirements with a goal to guarantee interoperability.
The file system of an appropriately formatted devices — for example, an SD card plugged into a digital camera — must be FAT16, FAT32, or exFAT.
SD cards with 2 GB or larger of space must be formatted with FAT32 or exFAT.
The goal is for digital cameras and their memory cards to be compatible with each other.

The DCIM Directory and Its Subfolders
Among other things, the DCF specification mandates that a digital camera must store its photos in a “DCIM” directory. 

The DCIM directory can — and usually does — contain multiple subdirectories. The subdirectories each consist of a unique three-digit number — from 100 to 999 — and five alphanumeric characters. The alphanumeric characters aren’t important, and each camera maker is free to choose their own.
On an Apple iPhone for example, the DCIM directory contains folders like “100APPLE,” “101APPLE,” and so on. On Panasonic cameras these are for example, 104_Pana, 118_Pana.

Inside each subdirectory are the image files themselves, which represent the images you take. Each image file’s name starts with a four-digit alphanumeric code — which can be anything the camera maker wants — followed by a four digit number.
For example, you’ll often see Panasonic files named P1040001.jpg, P1180002.jpg, and so on. Each image folder having 0000-0999 image sequence number before incrementing the first four alphanumeric number - for example P104 to P105.
The code doesn’t really matter, but it’s consistent to ensure the photos you take are displayed in the order you took them.

DCF is a “de facto” standard, which means that enough digital camera and smartphone makers have adopted it that it’s become a consistent standard in the real world. The standardised DCIM format means digital camera picture-transfer software can automatically identify photos on a digital camera or SD card when you connect it to your computer, transferring them over.

The DCIM folders on smartphones serve the same purpose. When you connect an iPhone or Android phone to your computer, the computer or photo-library software recognises the DCIM folder, notices there are photos that can be transferred, and often offers to do this automatically.

DCIM may not be the most obvious name the first time you see it — how about “Images or Photos”? — but it’s more important that it’s a standard.
 If every digital camera manufacturer or smartphone operating system had its own unique pictures folder, software programs wouldn’t always be able to automatically find photos on a connected device.
You wouldn’t be able to take an SD card from one camera and plug it directly into another digital camera, accessing the photos without reformatting the device or rearranging the file system.

Ultimately, just having a standard is important — whatever the standard is.
That’s why the DCIM folder has followed us from point-and-shoot cameras to smartphone and even tablet camera apps.
The Picture Transfer Protocol, or PTP, isn’t the same as the DCF standard, although  it serves a similar purpose. It’s been superseded by MTP and other standards, but PTP is supported by Android devices and iPhones for communicating with photo-management applications that support this standard.

If you want the history and background to the DCF system have a look here on Wiki

Macro Zoom and AF Macro  Modes on Panasonic cameras

The new feature introduced on the FZ300/330/1000/2000/2500 is the macro zoom mode.

This mode sets the camera to its widest angle setting (25mm EFL) and then to provide additional magnification uses digital zoom up to x3.

Allowing a close focussing distance mode of just 1cm (under 1/2 inch) can prove challenging with lighting set ups. Natural history photographers may also come across the problem where insects may not allow you to get this close before flying off.

In video where the image resolution isn't needed to be as high as in stills photography the results can be quite good, especially if you shoot in 4K mode.

Whilst the choice of mode will be dictated by the subject size and camera to subject distance some of the best choices will still rely on the use of close up lenses to allow longer focal lengths/greater working distances to achieve the optimum image quality.

The close up lenses are supplied in sets of usually 4 or they can be purchased as individual strengths.

The usual range is #1,#2,#4 and #10.

To get a better understanding of how these work if you set the camera to manual focus and set the focus point at infinity then if you were to put a #1 dioptre lens In front of the main lens you would find that objects just one metre away will be in sharp focus.

attach the #2 lens and the infinity focus will now be 50cms and with the #4 lens it will be 25cms.

So we can get good image size at distances which allow insects etc., to be filmed without spooking them off.

Of course if you focus the lens closer than infinity the corresponding near focus point will be closer as well.

You will find how these distance change in the article about close up lenses here







The mode is selected on the FZ300/330 with the push button on the lens barrel (assuming you haven't re-programmed this button to give FF/SS changes)








This first image is with the AF macro mode set and the camera lens to subject about 15cms (6 inch). The model car is about 10cms long (4 inch).








The second image is with the lens set to 35mm EFL






Switching to macro zoom the camera zooms out to 25mm and then I used the macro zoom option to bring the lens back to 35mm EFL.










Again using the 2x digital zoom to bring the lens to 50mm EFL







With the macro zoom almost fully engaged this image at 70mm is just showing signs of loss of resolution when enlarged to A4 print size







In contrast this image with the lens set to give 160mm EFL and with a 250D achromatic lens fitted #4 the image quality is still excellent at the working distance is 24cms allowing more opportunity to get good lighting onto the subject using ring flash or LED light rings.







In this last shot you can see the field of view and magnification when the lens is set to 600mm EFL. The camera is still at 24cms subject to camera distance