How to get clean background ?
By Sunny Chir

There have being many queries on how to achieve bright and creamy backdrop from a number of friends .


A good understanding of the lens is essential in order to understand and achive what I am trying to share. My preference for a 180mm dedicated macro lens is for its longer working distance so that I do not have to work as hard to get my shots. Why do I use a 180mm Macro lens and not a shorter focal length like the 90mm which is lighter and cheaper . The answer is simple, butterfly shooter need a longer working distance, as most of the butterflies would not let you infringe into their safety distance. They would have scooted off well before you can bear your 90mm on them to achive a 1:1 magnification. What about a 70-300 zoom? Would not it be better and more flexible with better reach ? The answer is :The design of zoom lens fair badly in Macro situation , the angle of view is large and it will include a lot of uneccessary clutters into your backdrop due to its large angle of view , and it does not have true close up capability despite many a manufacture slapping a Macro label on them. A dedicated macro lens is a prime lens with lens arrangement designed specifically for 1:1 magnification that produce pin sharp picture . With the lens question out of the way we can now proceed to how to use it.


The degree of blur to the background are predicated by a few things, some are fixed while others are variable and depending on the scene : 1. The focal length and its angle of view of the lens : The longer the focal length with a narrower angle of view ( of the lens) will throw the background into a blur or "bokeh". The Tamron 180 mm Macro lens I am using has an angle of view of around just 3 degrees and it throws object in front and beyond the intended DOF into a creamy blur fairly easily. 2. Aperture selected , the larger the aperture ( smaller aperture number) the less depth it will cover beyond the subject and the more out of focus the background will be. 1 and 2 once selected are fixed but the next two items are variable . 3. The distance of your lens to the subject , the closer you are to the subject the more diffuse the background will be. 4. The distance of the object behind the subject , the further it is the more diffuse it will become. Normally I try to fill the subject almost to full frame, this can be as close as 50 cm from the subject and play with the aperture to get the effect that I want. At this close range a slight tilt of the lens will produce a significant change in the quality of the background bokeh , making fine adjustment possible.


There are two modes in using the flash , First curtain and Rear curtain syn (2nd curtain syn) . With First curtain syn flash , the flash is the sole provider of light , the camera will meter the exposure assuming the flash is the only source of light , it fires when the first curtain of the shutter is opened, even with the most powerful flash in the marker , its reach is limited , hence object beyond the reach of the flash is not illuminated, and the background is dark. Second curtain syn is effectively a " two exposures" shot. when the first curtain opened it allows ambient light to be registered on the sensor , and just before the second curtain closes, the flash is fired to illuminate the object in front, thus giving the overall exposure a brighter backdrop. I am utilizing a Canon EX580 hotshoe flash as Fill-flash, pointing directly at the subject without any diffuser . The Canon Flash is fairly sophisticated , first it fires a preflash when the shutter is triggered , the "bounce-back" from the preflash is then used by the flash and camera system to compute the proper amount of fill -flash to illuminate the subject . And just before the 2nd curtain closes , the FILL FLASH fires to illuminate the subject in front. My take on diffuser over a Canon flash is, the flash ended up working harder as the diffused light will result in a reduced "bounce back" from the subject, this lead the system to think it requires a stronger pulse to illuminate the subject..... all because of the diffuser ! Some Onboard flash do have 2nd curtain capability, though not as sophisticated as those stand-alone flash unit, and the light can be harsh. To compensate this you can use an opaque drink container, or an old film canister to diffuse the flash. I have seen shots taken with onboard 2nd curtain flash and some of them are pretty good. It might worth your while to experiment with your onboard flash if weight and cost is a consideration. Do note that with the inbuilt flash position low, in some situation the flash reach can be obscured by your lens/hood. That basically sums up all there is to know, on how to get a bright and clean background , so that your subject can stand out in its full glory. Now, you will have to go out there and work on it ! "WAIT Sir ! ... What F setting you use ? " Butterfly is a very thin object and if your parallel your sensor to its broadside , you do not need F/16 to cover it . My preset is F/8 , but routinely open up to F/5.6 or even F/3.5 if the situation dictates it . ...... that is why the F setting dial is there ,it is not there for ornamental purposes but for you to adjust as require to get the desired effect you want !! :)) Hope the above short notes helps !