Why do you buy fast lenses/cameras?

Started 4 months ago | Polls
kiwi2
kiwi2 Veteran Member • Posts: 4,755
Re: Why do you buy fast lenses/cameras?
1

trungtran wrote:

Honestly i rarely shoot below F2.8.

I photography people singles and groups. I don't like the one person in focus and the other person not. If i don't have a speedlight or can't use it then sure i use the faster aperture, but i rather just use my zoom and have most people in focus.

But that's just you.

For all the scenes in this clip I didn't shoot f/2.8 or above. Everything was f/2 to f/2.5.

Sometimes nothing beats being able to gather as much light as possible in a certain time frame.

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Crash N Burn
Crash N Burn Regular Member • Posts: 119
Re: Why do you buy fast lenses/cameras?

Reilly Diefenbach wrote:

Abstaining. The absolute last thing I want on my camera is one of these two pound f1.4 monstrosities. The world really doesn't need another one eyelash in focus blurry nose and ears masterpiece :^)

An understandable position.

DSLRs have that clumsy AF fine tune confound, whose value varies as a function of focal length and subject distance--a problem rendered all the more apparent with fast glass. Then, there's that amusingly antiquated focus and recompose. Lastly, let's not forget to give credit where it's due: the Nikon Z's are very good at eyelash focus, from what I've heard.

You'd be surprised at how useable fast lenses are on, say, a Sony FF mirrorless body.

tony field Forum Pro • Posts: 10,327
Re: Why do you buy fast lenses/cameras?
1

Michael Fryd wrote:

tony field wrote:

Michael Fryd wrote:

Don't forget:

  • Brighter Viewfinder
  • More accurate auto focus

If you are using a camera with a padf system, why would an F 1.4 lens provide more accuracy then an F 4 lens or F 2.8 ??

Take the Canon 5D 4 for instance. There are 61 Autofocus points, but not all are created equal. Each point has from one to four PDAF sensors in various orientations; horizontal, vertical, right diagonal, and left diagonal.

Some of the sensors work with lenses that's f/8 or faster, some work with lenses that are f/5.6 or faster.

A few of them are slightly higher precision, but only work with lenses that are f/4 or faster.

Five AF points near the center offer the highest precision, but only work with lenses f/2.8 or faster.

Take the center AF point. With an f/8 lens the horizontal and vertical PDAF sensor will do a good job with most lenses. However, the right and left diagonal sensors can provide higher precision results with lenses faster than f/2.8.

As the camera focuses with the lens wide open, you get the benefits of the high precision focus points with an f/2.8 lens, even if you are shooting at f/8.

Thus the f/2.8 version of the 70-200 lens may yield more accurate focus than the f/4 version, even if you are shooting at f/4 or slower.

with the Canon systems you do not gain more focus precision with a 1.4 lens than you do with the 2.8 lens. As Marianne Oelund pointed out years ago the Canon F 2.8 focusing system does not seem to provide more precision than the Nikon F 5.6 focus system.

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Michael Fryd
Michael Fryd Forum Pro • Posts: 11,795
Re: Why do you buy fast lenses/cameras?
2

tony field wrote:

...

with the Canon systems you do not gain more focus precision with a 1.4 lens than you do with the 2.8 lens. As Marianne Oelund pointed out years ago the Canon F 2.8 focusing system does not seem to provide more precision than the Nikon F 5.6 focus system.

Correct.  An f/2.8 lens can provide more accurate focus than an f/4 lens.  However, there are no further improvements from moving to a lens faster than f/2.8.

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Bob A L Senior Member • Posts: 2,161
Re: Why do you buy fast lenses/cameras?

Personally, for me and not a recommendation. Absolutely no reason to buy fast lenses with the high iso, low light capabilities of modern digital cameras. Plus other reasons for me not to buy them - huge and too heavy, cost way too much money, no reason to want super  thin dof.

Mackiesback
Mackiesback Senior Member • Posts: 7,055
Re: Why do you buy fast lenses/cameras?

Michael Fryd wrote:

Don't forget:

  • Brighter Viewfinder
  • More accurate auto focus
  • They tend to be sharper (a high quality f/2.8 lens is likely sharper at f/3.5 or f/5.6 then a lens with a maximum aperture of f/3.5).
  • The wider apertures tend to be bundled with other features (i.e better build quality, weatherproofing, better optical quality).

That would be option number 4.

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tko Forum Pro • Posts: 12,946
well

Michael Fryd wrote:

tko wrote:

trungtran wrote:

If i want better IQ in the low light, i use a bigger sensor

Bigger sensor don't gather more light, but bigger lenses do.

In terms of the lens, the angle of view and aperture diameter are the two main factors in how much light you gather. Generally, for a given angle of view, it's easier to find a lens with a large aperture for larger sensor cameras.

The OP implied he used a bigger sensor instead of of a bigger lens. They tend to go tougher, but you still need that faster lens.

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OP Lee Jay Forum Pro • Posts: 54,893
Re: well

tko wrote:

Michael Fryd wrote:

tko wrote:

trungtran wrote:

If i want better IQ in the low light, i use a bigger sensor

Bigger sensor don't gather more light, but bigger lenses do.

In terms of the lens, the angle of view and aperture diameter are the two main factors in how much light you gather. Generally, for a given angle of view, it's easier to find a lens with a large aperture for larger sensor cameras.

The OP implied he used a bigger sensor instead of of a bigger lens. They tend to go tougher, but you still need that faster lens.

At the same f-stop, a bigger sensor is faster but the reason it's faster is that at the same angle of view the longer focal length lens has a larger entrance pupil.

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Michael Fryd
Michael Fryd Forum Pro • Posts: 11,795
Re: Why do you buy fast lenses/cameras?

Mackiesback wrote:

Michael Fryd wrote:

Don't forget:

  • Brighter Viewfinder
  • More accurate auto focus
  • They tend to be sharper (a high quality f/2.8 lens is likely sharper at f/3.5 or f/5.6 then a lens with a maximum aperture of f/3.5).
  • The wider apertures tend to be bundled with other features (i.e better build quality, weatherproofing, better optical quality).

That would be option number 4.

Yes.

But if the goal is to understand why people buy fast lenses, you probably don't want a survey where lot's of people select "other."

The survey provides far more insight when you can tell the people who wanted a brighter viewfinder from the people who wanted better weather sealing or more accurate auto focus.

On the other hand, if you are trying to promote a particular viewpoint with respect to shutter speed and depth of field, then it may sense to strategically omit common reasons.

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Michael Fryd
Michael Fryd Forum Pro • Posts: 11,795
Re: well

Lee Jay wrote:

tko wrote:

Michael Fryd wrote:

tko wrote:

trungtran wrote:

If i want better IQ in the low light, i use a bigger sensor

Bigger sensor don't gather more light, but bigger lenses do.

In terms of the lens, the angle of view and aperture diameter are the two main factors in how much light you gather. Generally, for a given angle of view, it's easier to find a lens with a large aperture for larger sensor cameras.

The OP implied he used a bigger sensor instead of of a bigger lens. They tend to go tougher, but you still need that faster lens.

At the same f-stop, a bigger sensor is faster but the reason it's faster is that at the same angle of view the longer focal length lens has a larger entrance pupil.

At the same aperture diameter and same angle of view, the light captured is independent of sensor size.

When we compare a crop body to a full frame, we seldom compare at the same focal length, as the result of the focal length depends on sensor size.

Why would you want to compare at the same f/stop?   The advantage of same f/stop is that we can maintain the same light per unit area on the sensor.   But different sensor sizes give us different noise levels at the same light per unit area.  That's no more a fair comparison that comparing at the same focal length.

If you want to compare at the same camera settings, use the same settings; same focal length, same f/stop, same ISO.

If you want to compare when you want similar results, then adjust the focal length to yield the same angle of view, use the same aperture diameter, and adjust the ISO to match.  (i.e. if your full frame is at 50mm, f/4 and ISO 800, your 2X crop body should either be at the same, or at 25mm, f/2, ISO 200.

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OP Lee Jay Forum Pro • Posts: 54,893
Re: well

Michael Fryd wrote:

Lee Jay wrote:

tko wrote:

Michael Fryd wrote:

tko wrote:

trungtran wrote:

If i want better IQ in the low light, i use a bigger sensor

Bigger sensor don't gather more light, but bigger lenses do.

In terms of the lens, the angle of view and aperture diameter are the two main factors in how much light you gather. Generally, for a given angle of view, it's easier to find a lens with a large aperture for larger sensor cameras.

The OP implied he used a bigger sensor instead of of a bigger lens. They tend to go tougher, but you still need that faster lens.

At the same f-stop, a bigger sensor is faster but the reason it's faster is that at the same angle of view the longer focal length lens has a larger entrance pupil.

At the same aperture diameter and same angle of view, the light captured is independent of sensor size.

Yes.

When we compare a crop body to a full frame, we seldom compare at the same focal length, as the result of the focal length depends on sensor size.

I do that comparison, frequently, because I'm focal-length-limited or using a prime.

Why would you want to compare at the same f/stop?

Because I can mount my crop and full-frame bodies to the same lenses.

The advantage of same f/stop is that we can maintain the same light per unit area on the sensor.

Correct.

But different sensor sizes give us different noise levels at the same light per unit area. That's no more a fair comparison that comparing at the same focal length.

Lenses are a real-world limitation.  I have a 70-200/2.8, but I don't have a 320/2.8 to put on my full-frame camera to compare to.  It would win easily if I did, but I don't.

If you want to compare at the same camera settings, use the same settings; same focal length, same f/stop, same ISO.

I don't have a reason to do that.

If you want to compare when you want similar results, then adjust the focal length to yield the same angle of view,

But real-world lenses can prevent that.

use the same aperture diameter,

My telescope doesn't have an aperture actuator.  The entrance pupil diameter is fixed, regardless of angle-of-view.

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Lee Jay

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Mackiesback
Mackiesback Senior Member • Posts: 7,055
Re: Why do you buy fast lenses/cameras?

Michael Fryd wrote:

Mackiesback wrote:

Michael Fryd wrote:

Don't forget:

  • Brighter Viewfinder
  • More accurate auto focus
  • They tend to be sharper (a high quality f/2.8 lens is likely sharper at f/3.5 or f/5.6 then a lens with a maximum aperture of f/3.5).
  • The wider apertures tend to be bundled with other features (i.e better build quality, weatherproofing, better optical quality).

That would be option number 4.

Yes.

But if the goal is to understand why people buy fast lenses, you probably don't want a survey where lot's of people select "other."

The survey provides far more insight when you can tell the people who wanted a brighter viewfinder from the people who wanted better weather sealing or more accurate auto focus.

On the other hand, if you are trying to promote a particular viewpoint with respect to shutter speed and depth of field, then it may sense to strategically omit common reasons.

At the risk of overthinking it yes. Ideally, it could be a list of all the benefits where you can select multiple choices.

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Michael Fryd
Michael Fryd Forum Pro • Posts: 11,795
Re: Why do you buy fast lenses/cameras?

Mackiesback wrote:

Michael Fryd wrote:

Mackiesback wrote:

Michael Fryd wrote:

Don't forget:

  • Brighter Viewfinder
  • More accurate auto focus
  • They tend to be sharper (a high quality f/2.8 lens is likely sharper at f/3.5 or f/5.6 then a lens with a maximum aperture of f/3.5).
  • The wider apertures tend to be bundled with other features (i.e better build quality, weatherproofing, better optical quality).

That would be option number 4.

Yes.

But if the goal is to understand why people buy fast lenses, you probably don't want a survey where lot's of people select "other."

The survey provides far more insight when you can tell the people who wanted a brighter viewfinder from the people who wanted better weather sealing or more accurate auto focus.

On the other hand, if you are trying to promote a particular viewpoint with respect to shutter speed and depth of field, then it may sense to strategically omit common reasons.

At the risk of overthinking it yes. Ideally, it could be a list of all the benefits where you can select multiple choices.

To be most useful, it should list the most common reasons.

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OP Lee Jay Forum Pro • Posts: 54,893
Re: Why do you buy fast lenses/cameras?

Michael Fryd wrote:

Mackiesback wrote:

Michael Fryd wrote:

Don't forget:

  • Brighter Viewfinder
  • More accurate auto focus
  • They tend to be sharper (a high quality f/2.8 lens is likely sharper at f/3.5 or f/5.6 then a lens with a maximum aperture of f/3.5).
  • The wider apertures tend to be bundled with other features (i.e better build quality, weatherproofing, better optical quality).

That would be option number 4.

Yes.

But if the goal is to understand why people buy fast lenses, you probably don't want a survey where lot's of people select "other."

Right now we're at 2.4% other, so I think we're good.

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Lee Jay

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Rexgig0
Rexgig0 Veteran Member • Posts: 6,403
Re: Why do you buy fast lenses/cameras?
3

Most of my “fast” lenses were chosen primarily due to factors such as a “pro” build and the optical engineering. The wide maximum aperture, which enables a faster shutter speed, was/is a bonus.

In some cases, a faster shutter speed, in low light, was the primary goal, and the better build quality and optical engineering were bonuses.

Shallow depth of field was never a primary consideration. If I open an aperture wider than f/5.6, it is usually due to the need to let more light reach the sensor

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By accident of availability, I learned to use Canon and Nikon DSLRs at the same time. I love specific lenses made by both Canon and Nikon, too much to quit either system. Dabbling with Leica-M is fun, too. I am, certainly, not an expert.

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Michael Fryd
Michael Fryd Forum Pro • Posts: 11,795
Re: Why do you buy fast lenses/cameras?
3

Lee Jay wrote:

Michael Fryd wrote:

Mackiesback wrote:

Michael Fryd wrote:

Don't forget:

  • Brighter Viewfinder
  • More accurate auto focus
  • They tend to be sharper (a high quality f/2.8 lens is likely sharper at f/3.5 or f/5.6 then a lens with a maximum aperture of f/3.5).
  • The wider apertures tend to be bundled with other features (i.e better build quality, weatherproofing, better optical quality).

That would be option number 4.

Yes.

But if the goal is to understand why people buy fast lenses, you probably don't want a survey where lot's of people select "other."

Right now we're at 2.4% other, so I think we're good.

The problem is that you don't know how many people chose not to respond because they didn't see their reason listed.

Suppose you get an even response with no more than 20 people selecting any one answer.  If there were 200 people who didn't answer, you don't have answers from over 70% of your audience, and that 70% is self selected to probably be those who would have selected "other".

The questions on the survey guide the responses.   One has to be very careful with designing the questions.   If you want to find out why people make decisions, you don't want to influence the results.  If you want to make a point, then you want to influence the results to support your position.

Here's a simple example of how words influence people, which is a better sale:

  • Up to 20% off on all items!
  • No more than 20% off on any item.

To most people, the former sounds like a better deal, but both say exactly the same thing.

Most Americans favor one of two political parties.  Let's call them "A" and "B".  Suppose there was a third party "C" favored by about 5%.

There's a big difference between the survey:

What party do you favor:

  • A
  • B
  • other

and

  • A
  • C
  • other

People are more likely to answer if they see their preference listed.  People who favor party "A" are likely to answer either survey.

People who favor "B" are more likely to answer the first survey, and not bother with the second.

Therefore the first survey should be used if you want a more accurate result.  The second should be used if your goal is to inflate the number of people who favor party "A".

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Mark_A
Mark_A Forum Pro • Posts: 15,066
For low light and narrow dof
2

I have two f1.8 lenses, two f2.8 lenses, and one f4.5-5.4 lens.

I buy fast lenses for better low light abilities and to be able to get a narrower dof when I want it.

Mark_A

perrrob
perrrob Junior Member • Posts: 48
Re: For low light and narrow dof

Mark_A wrote:

I have two f1.8 lenses, two f2.8 lenses, and one f4.5-5.4 lens.

I buy fast lenses for better low light abilities and to be able to get a narrower dof when I want it.

Mark_A

Same here ... I also prefer a light photography kit (especially when on vacation).

As I'm just a hobbyist, all my "fast glass" are light primes (f/1.8G) and my zooms are lighter variable aperture lenses which I use in good light (ie. outside).

Whenever I go out, I always have at least my 2 essential lenses (16-85 zoom and 35 f/1.8 prime). I then add additional lenses according to what I might need that day.

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Reilly Diefenbach
Reilly Diefenbach Forum Pro • Posts: 13,506
Re: Why do you buy fast lenses/cameras?
5

Crash N Burn wrote:

Reilly Diefenbach wrote:

Abstaining. The absolute last thing I want on my camera is one of these two pound f1.4 monstrosities. The world really doesn't need another one eyelash in focus blurry nose and ears masterpiece :^)

An understandable position.

DSLRs have that clumsy AF fine tune confound, whose value varies as a function of focal length and subject distance--a problem rendered all the more apparent with fast glass. Then, there's that amusingly antiquated focus and recompose. Lastly, let's not forget to give credit where it's due: the Nikon Z's are very good at eyelash focus, from what I've heard.

You'd be surprised at how useable fast lenses are on, say, a Sony FF mirrorless body.

Did buybuybuy just break wind in the forum and try to blame it on CnB?  PU!

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sportyaccordy Forum Pro • Posts: 15,357
Re: Why do you buy fast lenses/cameras?

Half and half. I use my standard zoom as a walk around so I like its IQ and ability to isolate subjects at the long end. Makes for an impromptu portrait lens. My 35 1.4 is my indoor lens so while the subject isolation is nice I mainly have it for light gathering.

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