How does focal length affect low light??

I have a d700, and a 50mm f/1.8. If i get a 35mm f/1.8 will it improve in low light shooting? Logically, if all the settings are the same, the 35mm should perform better since the distance light has to travel is 35mm as oppose to 50mm. Therefore I can increase my shutter speed.

Am I right? if not please explain.

Thanks all

The aperture number gives the amount of light that will reach the sensor. Imagine a bucket under a faucet. If you bring the bucket closer to the faucet and the valve stays the same it won't fill up faster. The same applies to aperture. The only exception is when you use extension bellows, but the metering system that we use now takes this into consideration and you don't have to compensate as we did when using the old manual lightmeter.

And second, the 35 1.8 is a DX lens. It won't cover the whole D700 sensor. If you want more light, you'll have to dig deep into your wallet and get the 1.4 lenses...

So assuming aperture is the same on two lenses, but they vary in length. The length of the lenses doesn't make a different.

I would think that the time it takes for light to travel thru a 35mm would be short than a 50mm. But then light travels pretty fast already so maybe a 15mm is not significant.

chowchow said:

So assuming aperture is the same on two lenses, but they vary in length. The length of the lenses doesn't make a different.

I would think that the time it takes for light to travel thru a 35mm would be short than a 50mm. But then light travels pretty fast already so maybe a 15mm is not significant.

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Right. And even if it takes more time to get there (which is insignificant when you know the speed of light), the amount of light will be the same for the same aperture. All this is theory.
Some lenses apparently are more luminous than another for the same aperture value. The aperture number on the lens is an aperture value that could be "slightly" different from the absolute value. But in our cases, we should not be concerned IMOHO.

chowchow said:

So assuming aperture is the same on two lenses, but they vary in length. The length of the lenses doesn't make a different.

I would think that the time it takes for light to travel thru a 35mm would be short than a 50mm. But then light travels pretty fast already so maybe a 15mm is not significant.

Click to expand...

For light to travel an extra 15mm after traveling 186,000 MILES per second can be considered relatively insignificant! Then again, 15 millimeters IS 15 millimeters!

That may take every bit of .0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001 second.

chowchow said:

So assuming aperture is the same on two lenses, but they vary in length. The length of the lenses doesn't make a different.

I would think that the time it takes for light to travel thru a 35mm would be short than a 50mm. But then light travels pretty fast already so maybe a 15mm is not significant.

Click to expand...

There's a rule of thumb to remember called the "Sunny 16" rule. When shooting a subject in full sun and setting the aperture at f/16, the shutter speed should be 1/ISO. If you have ISO set at 200, then the shutter speed is 1/200.

Note that the rule doesn't included anything about the focal length of the lens. That's because it doesn't matter.

You need to study up on the Exposure Triangle. There's lots of info available, but here is a place to start.

This is basic information that MUST be understood if you're going to progress in photography.

BWTHDIK

@chow chow- Marcel covered most of your questions. The Nikon 35mm f1.8G DX lens will vignette if you use it with your D700. If you want a cheaper alternative at 35mm, the Rokinon might be the answer for you if you don't mind MF.

http://www.amazon.com/Rokinon-Angle...2?s=electronics&ie=UTF8&qid=1324954454&sr=1-2

I have been interested in a faster lens. I find that I am limited by the low speed whenever I set to aperture priority. This makes my photo blur. However, if I set to speed priority, the images get darker or grainier if ISO is high.

Without flash, my f3.5 max kit lens just cannot meet the need. So i am looking at f1.8.

However, with a DX camera, I am still not sure if I should go for 35 or 50 mm. 35 mm seem right for indoor but most times, at that distance, one could have use flash. Indoor are likely to require to 11-16 mm lens.

Anyone has this experience to share?

Bukitimah said:

I have been interested in a faster lens. I find that I am limited by the low speed whenever I set to aperture priority. This makes my photo blur. However, if I set to speed priority, the images get darker or grainier if ISO is high.

Without flash, my f3.5 max kit lens just cannot meet the need. So i am looking at f1.8.

However, with a DX camera, I am still not sure if I should go for 35 or 50 mm. 35 mm seem right for indoor but most times, at that distance, one could have use flash. Indoor are likely to require to 11-16 mm lens.

Anyone has this experience to share?

Click to expand...

To get 1.8, you'll have to be happy with the 35. the 11-16 is 2.8. If 2.8 is OK, the Tamron 17-50 is very good and half the price of the 17-55 Nikon. I was fortunate to get the Nikon after the Tamron because it was damaged and I had it fixed, but quality wise, they are close to each other. And you get stabilization with the Tamron.

chowchow said:

I have a d700, and a 50mm f/1.8. If i get a 35mm f/1.8 will it improve in low light shooting? Logically, if all the settings are the same, the 35mm should perform better since the distance light has to travel is 35mm as oppose to 50mm. Therefore I can increase my shutter speed.

Am I right? if not please explain.

Thanks all

Click to expand...

As others have stated, f/1.8 is f/1.8 regardless of focal length. So using a shorter focal length lens of equal maximum aperture will not allow you to use a faster shutter speed. What has not been mentioned in terms of how focal length can effect shutter speed in low light is that with a shorter focal length lens you can use a slower shutter speed and still avoid camera shake. The general rule-of-thumb is that the minimum hand-holdable shutter speed is approximately the reciprocal of the focal length of the lens. Example: the minimum hand-holdable shutter speed of a 35mm lens would be 1/35 second (1/30 being the nearest available), whereas a 50mm lens would require 1/50 second (2/3 stop faster). As I said, this is only a general rule-of-thumb. I have hand-held a 300mm f/2.8 @ 1/15 second and got a razor sharp image (no VR!).

Marcel Carey said:

And second, the 35 1.8 is a DX lens. It won't cover the whole D700 sensor. If you want more light, you'll have to dig deep into your wallet and get the 1.4 lenses...

Click to expand...

Another less expensive option is a used 35mm f/2.0. Very nice lens for FX unless you can spring for the f/1.4