Thursday, March 15, 2012

DAY - 74 Bokeh Test: AF-S 50mm vs. Ai-S 50mm

Lighting info:
1 SB 26 @ 24mm 1/4 power snooted with shoot through umbrella. All shots at ISO 100 1/80s triggered with pocket wizard plus IIs

DAY - 74 Bokeh Test: AF-S 50mm vs. Ai-S 50mm
View On Black

For close inspection see the Original

Yesterday I had several people ask me if my Nikon AF-S 50mm f/1.4 G was really worth the price and how did it compare to the relatively cheaper AF-S 50mm f/1.8 G Lens. Here is what I can say about the 50s I have used.

Nikon AF-S 50mm f/1.4 G: Body is plastic but feels very solid, fastest, most accurate auto focus of any lens I have every used, This is my do everything lens, and the bokeh is great.

Nikon Ai-S 50mm f/1.2: Beautiful! This lens is absolutely awesome. I love to use it, and it has the smoothest focusing ring of any manual or autofocus camera I have ever used. Bokeh is to die for and I am proud to own this lens.

Nikon AF 50mm f/1.8: This is older nikon 50 1.8 without a focus motor. It is plastic, feels cheap, won't autofocus on entry level nikons. The images from this lens are very good and it at the price of around $100 used you should own this lens if don't already own a faster Nikon 50mm. I don't own one myself, but I have used one on my nikon D90 and I was impressed with the results.

Nikon 50mm f/1.4 D: I have not used this lens yet. I considered buying this lens so I could use it on my manual focus 35mm camera, but I already owned a Ai-S 1.2. This is why I decided to go with the AF-S for my D90 regardless of price difference, I knew the AF-S would focus faster.

Nikon 50mm f/1.8 G: I have also not used this lens, but I expect that it is quite good and will focus nearly as fast as 1.4 and why most people aren't going to pay the price for and additional 2/3s of a stop I would say this lens is probably great. Being the newest Nikon 50mm, good luck finding a used lens at a discount price.

And for the cannon shooters, I have used the $110 canon EF-II 50mm f/1.8 lens and what I can say is that it is better than its Nikon equivalent. While I always go for Nikon glass, this canon lens is so good I insisted on buying one for my mother canon rebel. The pictures are great and the focus is good, but a little noisy. If you are a canon shooter get one today.

One of my questions yesterday was in regard to the fact that there was only a .4 difference between the 1.4 and 1.8 lens. I responded to the question that the difference was 2/3s of a stop, and it is significant. Difference between f/16 and f/15.6(which is not actually a stop) is not the same at the difference between f/1.4 and f/1.8. Let me explain aperture a little more clearly.

As some of you may know aperture is based on the square root of 2. Ok, but why and what does it really mean. To start with exposure values, or EV are not linear i.e. 1,2,3, the counting numbers we are used to. EV is based on 2; meaning that with each full EV stop the light energy doubles, or is halved if you decrease by one stop. Consider a fixed aperture (we don't care what) with an exposure of 1s; if we need to get twice the light, we would increase the exposure to 2s. This is very intuitive and easy to understand, like wise we would reduce the exposure to 1/2s if we need 1/2 the light. I recently had to correct a sales person at a camera store when another customer asked about the odd numbers for aperture; the clerk answered, “It is just the nomenclature that they use." This answer is wrong! Let's do some simple math figure out what is going on.

The Aperture is roughly a circle, and f-number = focal length/aperture diameter. Ok, the area for a circle is Area=PI*radius^2(squared). With a fixed shutter speed, we need to double the Area to double our light energy; therefore 2*A = 2*PI*radius ^2. Pi is constant, and each time we double our area with double the radius squared; which is confusing. Let's re-write our equation. 2*A=pi*(sqrt(2)*r)^2. When we bring the 2 inside the parentheses with the radius, which is squared, 2 becomes square root of 2 to keep our equation equal. Sqrt(2)=1.41......, which is approximately 1.4, a number we recognize; 1.4^2=1.96 approximately 2. This is why the whole f-stops are: 1.0,1.4, 2.0, 2.8, 4.0, 5.6, 8.0, 11, 16, etc. Notice the pattern that every other number is doubling.

One of the biggest differences in the bokeh of these two lenses is that the aperture blade of the Ai-S lens form a octagon, you can see this when stopped down to f/2.0. The AF-S lens keeps an aperture, as close to a circle as you can get through out the aperture range, and the bokeh shape does not change much between stops.

Bottom line. I think both lenses are great! The AF-S is super fast to focus and it is a sharp looking lens. The Ai-S is a work of beauty. It looks way classier than the AF-S lens. Which is better? You decide which takes a better picture. I can say that the Ai-S will not meter with any entry-level Nikon and not even with my middle level D90. This really bothered me at first, but I quickly learned my exposures for ambient light with out the aid of a meter. Being digital, you get instant feedback when you check the LCD. The AF-S will work flawlessly on any digital Nikon body; from the entry level D3000, to the new flagship D4. Was the AF-S lens worth the price? Yes it was, and I have never regretted it. Was the Ai-S lens worth it? Yes it was; I can't seem to part with it, I considered selling it to fund a macro lens but I can't part with this beautiful piece of glass. Am I insane for owning both of these lenses? Most certainly, I am not a professional photographer and I have yet to make the first dollar with my photography. I am a passionate amateur photographer who is completely obsessed, I spend most of my day thinking about my photos and often spend days, weeks, or even months thinking about and composing a photograph in my head before I ever click the shutter.

Until tomorrow,

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