Photo Larry

Depth of Field Determination

September 10, 2008December 24, 2008

A fairly simple way to determine Depth of Field (DOF) when using an SLR camera is by following some simple steps.? There are three factors which determine how ‘deep’ or ‘shallow’ your photo is rendered.? First is the distance between the focal plane(camera) and the subject.? If you are close to the subject, say a few feet, without other considerations, you will get a low DOF or in lay terms, the background will be blurry.? If you are far away, say across a large room, again other factors aside, you will get high DOF or in lay terms, the background will be clear.? Second is the focal length of your lens.? At shorter lengths (for sake of discussion 20mm-100mm approx) , other factors ignored, you should get deep DOF (clear background).? At longer lengths (for sake of discussion 200mm and up), you should get shallow DOF (blurry background).? Third is aperture (the size of that tiny hole that opens and closes).? If you use an f-stop of f2 or f4 you should get shallow(low) DOF (blurry background).? If you use an f-stop of f16 or f22 you should get deep(high) DOF (clear background).? F stop is the size of that hole and the numbers start from largest opening (f1) to smallest opening(f32 for most SLR lenses).? So those three factors being said, if you combine them, here is what you should get:

Focal Length (short) + Aperture Wide(f2) + Distance from Subject(close) = Blurred background(low DOF) mostly because of the wide aperture
Focal Length (short) + Aperture Wide(f2) + Distance from Subject(far) = Blurred background(low DOF) mostly because of the wide aperture
Focal Length (short) + Aperture Narrow(f32) + Distance from Subject(close) = Clear background(high DOF) mostly from the narrow aperture
Focal Length (short) + Aperture Narrow(f32) + Distance from Subject(far) = Clear background(high DOF) mostly from the narrow aperture
Focal Length (long)? + Aperture Wide(f2) + Distance from Subject(far) = Very blurred background(low DOF) because of the long focal length and wide aperture
Focal Length (long)? + Aperture Wide(f2) + Distance from Subject(close) =not possible, subject cannot be close with this focal length
Focal Length (long)? + Aperture Narrow(f32) + Distance from Subject(close) =not possible, subject cannot be close with this focal length
Focal Length (long)? + Aperture Narrow(f32) + Distance from Subject(far) = Fairly clear background(low DOF) mostly from the narrow aperture(the long focal length should lessen clarity)

Of course the in between values here will yield different results but hopefully if I explained well enough you should be able to calculate it approximately.? For example, 22mm lens, f8, subject=close should give you moderate DOF (somewhat clear background).? If you wanted it totally clear, use a smaller f stop(f16,f32,f64).

A few more examples: 300mm, f4,? subject(far) should give you a very blurry background(low DOF). 300mm, f16, subject(far) should yield somewhat clear background(moderate DOF) due to aperture.? See where I am going with this.? In general, mostly you will not determine subject distance.? What you can vary is the aperture and the focal length(possibly with a zoom lens).? In Summary,? to get more DOF(clearer background), use a small aperture and/or short lens.? To get less DOF(blurrier background), use a large aperture and/or long lens.? Typically for portraits, 100mm lens, f2 or f4, subject at moderate distance should yield a very blurred background(low DOF).? Hopefully my experience with these variables will help you to be a better photographer.

USA Wifi Hotspot Options

September 9, 2008December 14, 2018

There have been some recent changes to the big providers of wifi hotspots, those which are not free. So here is an update with all currently available wifi options in the USA. I currently use TMobile which provided hotspots at all Starbucks, Borders, Fed Ex Kinkos, and some hotels and airports. However Starbucks decided to cancel their contract and change to ATT. Also Fed Ex canceled their contract for service. You cannot access wifi any longer at Kinkos locations. All Starbucks locations now are ATT Wifi spots. Tmobile customers will always have roaming access but the login process needs improvement. ATT contracted wayport, a third party provider of network access points. Most of the Starbucks locations have been successfully transitioned. But there are a few of them which either do not allow login properly or simply are non-functional. TMobile currently charges 19.99 a month (if you have cell service with them, otherwise 29.99).? Another solution for paid wifi access from a laptop, PDA, or any 802.1x capable device, ATT Wifi offers several locations.? ATT charges 19.99 for people who do not have their DSL services at home. If you do, costs are 9.99 or free depending on the level of broadband you have at home. The drawback I found to this option was that most of their hotspot locations (McDonalds, Starbucks, Hotels) were implemented with only a DSL line. Therefore if more than one person was using the location, speeds sucked. Another paid option is called Boingo. They contract with other providers(like ATT) to offer access from almost any paid location. See list below for rates and location info. If you just refuse to pay, there are many free wifi hotspots in most cities. These are usually at independent coffee shops and other places. Sometimes they are much less reliable or may be down since you never pay for them. Many major cities do offer free service at local libraries. These are reliable and usually on a fast backbone. The only exception to that which I have found is in smaller towns where the backbone is saturated or not high speed.? One last thing to mention, cell companies provide wifi access over their cell networks too.? You need to purchase a special proprietary card which usually is PCMCIA compatible.? Besides that cost, you have to join a yearly plan with monthly costs varying from 49 to 89 dollars.? This is the most expensive option.? It is usually only used for business users and services are paid by the employer. For information on these services, visit Verizon, Sprint, ATT cellular websites.? So in quick sum, options: