Tuesday, August 14, 2012

Food Photography-Chapter 3-How Photography Works


How Photography Works


“Your first 10,000 photographs are your worst.” Henri Cartier-Bresson.

Henri Cartier-Bresson was right. Photography takes practice; it also takes knowledge of what makes it work before technique can be applied. It is both an art and a science.

The word photography comes from the Greek words photos, meaning of light and graphic, meaning brush and combined it means painting with light. Once upon a time the light would strike light sensitive chemicals (silver halides) and a latent image was formed. This latent image was then developed into a negative and then printed on paper. Now it is light hitting a sensor and the digital image is saved on a chip. That image is displayed on a computer or printed on paper. Sadly most pictures never make it off the chip.

So basically it all comes down to the light. All you have to determine how much of that light needs to hit the sensor and how it is focused. Well, composition is very important too. Your camera can do the first part automatically and there’s nothing wrong with allowing it to most of the time. It does help to know how and why things happen so you can manipulate the exposure, so let’s start with the basics.

Basic settings- The Trinity of exposure.

There are three elements that make up exposure and they are ISO, shutter and aperture. Change one and you have to change at least one of the other two. Let me explain each of them a bit and then I’ll explain how to make adjustments, and why you would want to.

Shutter- The shutter is a device that opens and closes in a camera to allow light to pass through the camera body to the imaging sensor or film. How long the light is allowed to hit the sensor is measured in fractions of a second. Standard settings are 1sec, 1/2, 1/4, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000, 1/2000. Many cameras can go below or above these numbers and newer ones have points between the standard speeds. The faster shutter speeds stop action. This isn’t really an issue for the food photographer as the food rarely moves and if it does you may not want to eat it. I want to add a word on shutter speeds. To handhold the camera keep the shutter speed at 1/30th minimum to prevent camera shake from showing up. With a zoom lens I’d recommend no slower than 1/60th. Below that use a tripod and a remote shutter release, or the self-timer. 

Aperture- The aperture is the opening inside the lens that can change in diameter to control the amount of light reaching a camera's sensor or film. The diameter is expressed in numbers called f/stops; the lower the number, the larger the aperture opening. The standard ones are f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, and f/22. Modern cameras can also give half stops. The bigger openings, the smaller numbers, tend to give a shallow depth of field while the smaller openings, the bigger numbers, give greater depth of field. I’ll explain this later.

ISO- ISO is adjusting the light sensitivity of the sensor. The higher the ISO, the faster the setting and the less light needed. So why not simply use a higher ISO? Well, there is a tradeoff here as the faster settings have more noise. This used to be known as film speed with the lower ISO having a finer grain and the higher ISO having larger grain. It isn’t exactly the same here, noise is actually stray electrical impulses striking the sensor, but it’s close enough for our purposes. Try to use the lowest ISO you can get away with, or let the camera decide by setting the ISO to automatic. Some cameras let you set a range of ISO. Standard film speeds are 25, 100, 200, 400, 800, 1600. ISO 400 needs half as much exposure as ISO 200 and twice as much as ISO 800. In digital there are points between.

Exposure- To put it all together exposure is made by a combination of ISO, shutter and aperture. Think of it this way. You have to get a whole bunch of people into a room and lined up against a wall. The ISO decides how many people need to come in. The higher the ISO, the less people have to get through the door and conversely the Lower the ISO, the more people have to get through. The aperture is the size of the door and the shutter is how long the door is open. If you have a really big door to the room it only needs to be open for a short time. If the door is small you have to leave it open longer. Each f/stop either doubles of halves the light, depending on which direction you go.  Therefore 1/60th at f/4 is the same as 1/125th at f/2.8 and 1/250th at f/2. Well, sort of the same and you’ll se what I mean when we discuss depth of focus.

Megapixels- Essentially this is how many pixels the camera’s sensor can record. The first digital camera I ever held was in the early ‘80’s and it was a Canon RC-250 xapshot that looked more like a binocular than it did a camera. It held 50 images on a removable floppy disk. The resolution was a mere 1/3rd of a megapixel.

There are quite a few people who will say that anything above 5MP is adequate for a poster-sized enlargement. I’ve even read that 6MP can be used for a billboard. The reason? The larger the print the further back you have to stand to view it. I usually shoot at 10MP in JPEG format.

Depth of Field- This is the area from foreground to background that is in focus. A shallow depth of field may only have the subject in focus while the background is a blur. We use this a lot in food photography.

White Balance/ Color Temperature- Light has a temperature, or color, depending on its source. This affects the colors of your photographs. The temperatures I’ve shown below are from an old Eastman Kodak book. The best way to check is with a color meter but there really is no need for that.

Light Source
Temperature in Kelvin
Color tint
Candle flame
1,700K
Red
Sunrise or sunset
2,000K
Reddish
100-Watt Incandescent Lamp
2,900K
Reddish/Yellow
Sunlight, Early Morning
4,300K
Slight Warm Tint
Sunlight, Noon
5,400K
Normal
Overcast Sky
6,000K
Blue Tint
Winter Sunlight
8,000K
Blue

This is why your indoor pictures without using a flash look a bit red and pictures on snow look a bit blue. Years ago film was predominately daylight film and balanced for about 5,000K. One added a blue filter to the lens to correct for indoor shooting and Tungsten film was available, balanced at 3,400K. Florescent lighting causes a nightmare of its own by being anywhere from yellow to green to even purple in hue. Now you know why some of the people in your portraits have green hair, and they’re not Goths. By the way, flash is daylight balanced so there’s no problem there, unless you try to mix flash, a light bulb and florescent lights.

The term White Balance is more of a video term and means to adjust to the lighting. All cameras can do this automatically and most will allow you to adjust as needed. I’ll let you in on a secret, for my DSLR I generally leave the white balance set on auto and it does a fine job. Once in a while I have to do a color correction to the image either in camera with the DSLR or on the computer.

JPEG or RAW?- JPEG stands for Joint Photographic Experts Group and is the standard for using images on the web. It is ready to use straight from the camera. RAW is more of a digital negative and requires a bit of work before it can be used, hence the name raw image. For most of the world I recommend JPEG since it is easier to use. If you know Photoshop, or a similar program, then by all means use RAW.

Camera Shooting Modes- There are a few ways to get the right exposure.

P Program- The camera sets both the shutter and the aperture. You can make some adjustments in this mode by using what is called program shift. Say the camera has set the exposure at 1/125th at f/8 and you want more depth of field. You shift to 1/60th at f/11 or 1/30th at f/16. Check your camera manual for how to do this, on mine I just spin the wheel on the back of the camera.

M Manual- You set both the shutter and the aperture. Here you have total control over the exposure. Generally you start by setting a shutter speed and find the aperture for correct exposure. It also works the other way around by setting the aperture and finding a corresponding shutter speed. The easier way is to use aperture priority or shutter priority.

A Aperture Priority- You set the aperture and the camera sets the proper shutter speed. Use this mode when depth of field is important. This is the mode I use most often.

S Shutter Priority- You set the shutter and the camera sets the proper aperture. Use this mode when you want to stop the action, or blur it.

Special Modes- In addition to the standard modes most modern cameras come equipped with a few modes for specific scenes. Some of these are; portrait, sports, close up, children and more. I have a compact camera that has a food mode on it, and the mode is basically worthless. 

Now let’s take a look at the equipment and get you even more confused.

5 comments:

  1. This is great since I'm teaching digital media this year and have been studying this information this summer!

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  2. Glad to be of help Karen. Feel free to use anything you need.

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  3. Thanks so much for doing this. I assume after the last lesson I should stop using my phone for pictures?

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  4. Thanks Joe. I'll talk about the iphone later, but a real camera is so much better. I have never had a restaurant take exception to my taking pictures and once you get used to bringing it in it gets easy.

    Chris

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    1. Oh, and I like your blog Joe. I added it to my blogroll.

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