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Showing posts with label Sigma. Show all posts
Showing posts with label Sigma. Show all posts

Macro Photography

Taking close-up pictures of small things is called "macro photography." I have no idea why. Perhaps because the small things in macro photography are generally larger than the things you are taking pictures of when doing "micro photography". If you really want to be pedantic then you should say you are doing "photomacrography".

What Kind of Camera


Point and shoot digital cameras can have remarkable macro capabilities, but for best results you want a single-lens reflex camera. These allow you to attach special-purpose macro lenses and show you in a bright optical viewfinder what you will get on the sensor.
A typical setup might be a Canon Digital Rebel XTi  with a Canon EF-S 60mm f/2.8 Macro USM . This lens is designed for the small-sensor Canon cameras and gives a working distance equivalent to 100mm on a full-frame photo camera. The lens is specified to focus down to "1:1" or "life size". This means that the smallest object you can photograph that will extend to the corners of the final digital photo will be the same size as the sensor inside the Canon Rebel camera, 15x22mm. A professional photographer might use Canon EOS 5D  and a lens designed for full Canon EF 100mm f/2.8 Macro USM. Confusingly, this lens is also specified to focus down to "1:1", but this time the sensor is 24x36mm in size, the old 35mm film standard. So you can't take a photo of something quite as small as with the cheaper equipment.
In the film world, the 35mm photo camera systems had comprehensive range of macro lenses and accessories and some medium format systems, such as the Rollei 6008 would have at least a few lenses and extension tubes. Only the extremely patient ever did macro photography with a 4x5 inch view photo camera.


Close-Up Lenses


Your eyes don't focus so great on really small things either. Do you try to pull your cornea a foot away from your retina? No. You stick a magnifying glass in front of your cornea. You can do the same thing for your normal lens. Unlike your cornea, it even has convenient threads for attaching a magnifying glass. The magnifying glass screws into the same place where a filter would go.



Macro Lenses

The best macro lenses are the latest autofocus mount models made by Canon and Nikon, typically in focal lengths ranging from 50 to 200mm. Each lens will focus continuously from infinity to 1:1. You can shoot the moon and capture the bear claw without stopping to change lenses or screw in filters. How do these lenses work? Do they just have a much longer helical than the 50mm normal lens? Yes and no.

 

Macro Zoom Lenses


Macro zoom lenses are not macro lenses. They don't allow significantly greater magnification than a 30mm or 50mm normal lens and they deliver low quality.


Exposure

Unless you are using close-up lenses, when doing any kind of macro work, you always have to consider the effective f-stop. Even if you are using the SLR body's built-in meter, which will correct automatically for light loss, you can't turn off your brain. Why not? Because the effective aperture affects picture quality.
Taking pictures through a pinhole results in tremendous depth of field but very low sharpness due to diffraction. This is why lenses for a 35mm film camera stop at f/22 and don't go to f/45 or f/64. Large format camera lenses provide these smaller apertures for two reasons: (1) the lenses are longer (f/64 on a 210mm lens is not all that small a hole); (2) the negative won't be enlarged very much.
If you're at 1:1 and have selected f/22 on the macro lens barrel, you need to look at the lens markings and/or the close-up exposure dial in the Kodak Professional Photoguide to learn that your effective aperture is f/45.
If you're using a handheld meter, you absolutely must use these corrections (e.g., meter says f/22 but you're focussed down to 1:1 so you set f/11 on the lens barrel).

Lighting


A good quick and dirty lighting technique is to use a through-the-lens (TTL) metered flash with a dedicated extension cord). A modern handheld flash is extremely powerful when used a few inches from a macro subject. That lets you stop down to f/16 and smaller for good depth of field. You can hold the flash to one side of the subject and have an assistant hold a white piece of paper on the other side to serve as a reflector. If you want a softer light, you will have enough power in the flash to use almost any kind of diffusion material. The TTL meter in the camera will turn the flash off when enough light has reached the sensor.
Lighting is the most important and creative part of any kind of photography.

Focus


With a depth of field of around one millimeter for precise macro work, camera positioning and focus become critical. If you have a good tripod and head, you'll find that you have at least 10 controls to adjust. Each of them will move the camera. None of them will move the camera along the axis that you care about.
That's why people buy macro focusing rails, e.g., Adorama Macro Focusing Rail . These are little rack and pinions capable of moving the entire camera/lens assembly forward and back. You use the tripod to roughly position the camera/lens and then the macro rail to do fine positioning.
The photos below are snapshots from the garden of the Getty Center. They were taken with a fancy Canon EF 180mm f3.5L Macro USM , but without a tripod.

Macro Photo Gallery










 information from photo.net


Celebration Of High-Speed Photography





A digital camera, some fast-moving subject, and a bit of knowledge about how to take the best pictures of moving subjects will launch you on the road to some of the most interesting photographs you’ve ever taken. Although some blurring can be effective in communicating a sense of high-speed motion, some photographers want the subject to be frozen in time to get some pretty special photographic effects.

High Speed Photography at Home

How totake high speed photos You can use this technique to take picture of exploding things like tomatoes, watter balloons, watermelons, or even you Canon photo camera as you smash it against a wall for not understanding the menus (Sorry, could not resist...)
 

Freezing fast motion (AKA High Speed Photography), can give some pretty special photographic effects. High Speed Photography is used in physics, health research, sports and more. This guide describes how to capture super fast movements using ordinary camera gear and a little home made electronics. I will describes the setup I used the problems I encountered and what I did to solve or work around them.

Capturing such images introduces a lot of challenges. How does one handle timing with exposures times

faster than 1/6000 second!?
We have to handle shutter lag, synchronize the flash and time the exposure to just the right moment.

But the shutter lag of any normal photo camera is so long that it will be all most impossible to time the exposures. And how do you synchronize the flash with an exposure time of less than 1/6000 second?
To work around the problems with shutter lag and flash synchronization, the exposure is done in a completely dark room. This way the shutter can opened without actually getting an exposure. The exposure time set on the photo camera just has to be long enough for the action to happen while the shutter is still open. Because the room is dark, the long exposure time will not have any effect on the final output (this is because no light enters the lens to hit the sensor / film)

To actually get an "exposure", a flash is fired. The flash light duration will now become the actual

exposure time.
SO now we need to see how long does it takes the flash to fire. It turns out that the output power of the flash, actually affects the duration of the light, so to get exposure times. If you need exposure faster than 1/6000 seconds, the output needs to be reduced.
Now we only need to synchronize the flash with the action we want to capture.
This can be done in several ways. For example synchronizing with a balloon puncture, can be done via sound. Impact-actions, like a BB Soft air gun pellets, can be triggered with a mechanical switch, like in the picture below. When the pellet hits the cd-cover it's pushed on to the switch, which then triggers the flash.
Here is my High Speed Photography setup and work flow (Balloon Shot).
 
The Gear:
  • Balloon (OK - we are going to nuke this one, so don't use your favorite)
  • Digicam
  • Tripod
  • Sigma Flash
  • Home made sound trigger (more info). If you do not have an optical slave you can use the Universal Sound Slave Circuit
  • Needle (or BB-gun)
  • Backdrop (I use a black Bristol sheet)
The Setup
First step is to set-up the scene. The black Bristol sheet is used as backdrop. The balloon, flash, microphone
and camera are placed like in to image below
high_speed_photography_setup.gif
Gear settings:
  • Flash: optical slave and 1/16 output power.
  • Camera: Exposure time: 1-2 sec. ISO 100-200 Aperture F 11-16 manual focus.
  • Microphone: The distance between the balloon and microphone, is used for synchronization. 50-70cm is good for balloon punctures :-)
Next step is framing and focusing:
While trying to stay within the best performance on the lens, I either zoom or move the tripod, until I have the desired framing. Focus can be obtained either automatic or manual, but do remember to switch to manual to lock focus, otherwise the camera will try to focus when the lights are switched off.
Now it's time to test the setup and lightning. All lights are switched off and the shutter is set to bulb.

To fire the flash I just clap my hands. Then I review the image on the camera, checking for exposure, framing, focus and DOF.
To get the correct amount of light / exposure, one can Increase or decrease:

- the strobe distance to the balloon

- the output power of the flash

- the aperture on the  photo camera

- ISO sensitivity on the photo camera
Taking the shot

The test is repeated until satisfactory result have been reached, and the real photo can be taken. This is done the same way as when testing, but instead of clapping, the balloon is punctured with a needle.
One could also just fill the balloon with water and shoot it with a BB Soft air gun :-)


Some cool High Speed Photography











information from smashingmagazine.com