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Old Aug 20, 2014, 1:23 AM   #1
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Default My Nikon AF-S 35mm 1.8G lens is not up to the mark - why???

Dear Friends,

I own a Nikon D5100, and have been using the 18-55 kit lens along with it, as you all know that this kit lens is superb for macros and closeups but not so great for landscape photography since the lens lacks the sharpness and also is crappy for low light shots, .

I heard lots of users praising the capabilities of the 35mm 1.8g prime lens, regarding its sharpness and its ninja ability to capture low light shots without sacrificing on shutter speed and iso .

So i decided to get my self this prime lens. but to my horror it all turned out to be wrong.

so i did a comparison test to find whats wrong.. pls note that all shots were made in aperture priorty mode and both at 35mm focal lenghts and all at the same lighting conditions and at ISO 100.

1. the first was a shot of some oranges on a table with the morning sun rays gleaming onto them.

first the 18-55 kit lens fixed at 35mm, the aperture was fixed at 5 the highest aperture the lens was capable of when zoomed to 35mm. when metered the shutter speed was fixed at 1/80th of a second. OK went ahead and took the shot

Now with the 35mm lens , again i fixed the aperture at 5, since i wanted to compare both the shots, But heres were the problem starts, When i metered the shutter speed was fixed at "1/60th of second" NOW HOW ON EARTH IS THAT POSSIBLE. why did the shutter speed become lower than the kit lens. i thought this prime lens was a fast one, and took superb shots in low light conditions. I really thought that the shutter would be meterd at somewhere in 1/100 and 1/200 range.

Why is this happening.

2. So i decided to take an out door landscape shot to check if this was the case again.

the shot was a rice paddy filed at 8:00 in the morning, sunrays shining brightly over the green rice field.

First with the kit lens, at 35mm, the aperture was fixed again at 5, when metered shutter speed was fixed at 1/3200 of a second. fast isn't it....OK

now with the prime lens and to my horror the shutter speed was fixed at 1/1600 of a sec.... WHAAAT lower than the KIT lens again.... WHATS GOING ON... why this lens is capable of capturing more light in right... then what wrong with the lens.

MY question to all is ....

is there something wrong with my lens, if yes how to find whats wrong and...

Please guys i need your expert advice... I EXPECTED more from this lens and now i am sad.
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Old Aug 20, 2014, 5:43 AM   #2
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The advantage of a large aperture lens is the large aperture. In your examples, you've chosen not to use the large aperture. In your first example, both lenses are set to f/5 and the camera's metering system selects very similar shutter speeds, 1/80 vs. 1/60, or about 1/3 EV difference.

This minor variation is common. From one exposure to the next, I would expect to see this kind of change. This could be caused by a minor change in the composition, especially if you were using spot or center-weighted metering.

The second example is more surprising. The difference between 1/3200 and 1/1600 is a full stop. That is, the metering system detected half as much light when using the prime as it did when using the zoom. This is likely to be a result of multiple factors. Minor variations in composition could cause some changes in the exposure system, but I suspect that it's much more likely that it was caused by a normal variation in your natural light source. For instance, a cloud could have drifted in front of the Sun when using the prime that wasn't there when using the zoom.

When relying on a natural light source, you should expect some variation in exposure settings from shot to shot, even without changing the lens. The variations you're seeing aren't anything to be alarmed about, and a more accurate test would use artificial lighting that is consistent from one shot to the next.

As I said in my opening paragraph, the advantage of a large aperture lens is the large aperture, which you've not used in your test shots.
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Old Sep 18, 2014, 11:21 PM   #3
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As TCav said, minor changes in composition can change the metering and exposure a bit. Did you use a tripod to get the EXACT same composition? And not all lenses transmit as much light as they should in theory-that's called T stops. F stops are how much light it should transmit in theory and t stops are how much light the lens actually transmits. Maybe the t stop on the 35mm lens is a little less than the f stop. Try to search "Nikon 35mm 1.8G DX T stops". And when you focus a lens really close the effective aperture can change causing a light loss. That's going to vary between lenses. So when you compare, you should be focused on something farther away, maybe at least 10 feet or so.
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