Question about focal length in relation to lighting

[SabrinaO]

Correct me if im wrong... but if the focal length is shorter, does the exposure come out brighter? Why is that? Is it true?

 

[Derrel]

...there's something not quite right about your question...

Does this question arise out of a particular experience, or a particular light metering incident using the camera's built-in light metering system?

 

[SabrinaO]

...there's something not quite right about your question...

Does this question arise out of a particular experience, or a particular light metering incident using the camera's built-in light metering system?

I had a shoot the other day and when I zoomed out the exposure was a little darker. I also just read a comment on DPF saying that if someone got a closer focal length they wouldn't have to use such a high ISO.

 

[SabrinaO]

...there's something not quite right about your question...

Does this question arise out of a particular experience, or a particular light metering incident using the camera's built-in light metering system?

:thumbup:

To OP: Are you sure you're not talking about... Aperture? ...Not that Aperture could be "shorter"... maybe I'm missing something here...

I know the smaller ap =less light... but i was wondering if it was the same for focal length. The longer the length the exposure will be darker? I don't know.

Heres a comment what someone said in another forum...

Instead of shooting at such a high ISO, you could have resorted to a shorter focal length lens which lets you get closer to the subject and captured the same image at a lower ISO.

 

[SabrinaO]

...there's something not quite right about your question...

Does this question arise out of a particular experience, or a particular light metering incident using the camera's built-in light metering system?

I had a shoot the other day and when I zoomed out the exposure was a little darker. I also just read a comment on DPF saying that if someone got a closer focal length they wouldn't have to use such a high ISO.

You know your Aperture can change when you zoom, right? Did you check to see if that's what happened, because that's what it sounds like to me, although I'm sure someone will correct me if I'm wrong.

That's right but I shoot in manual so I don't think it would of changed on me. But maybe i just thought it happened. Im not 100% sure. I just thought I noticed it during the shoot when I was chimping.

 

[Nikon_Dude]

Focal length on it's own does not change exposure, but as had been stated above, zooming often changes the aperture. If you have a basic lens, you'll see a number on it such as f3.5-5.6 This gives you the maximum aperture throughout the focal range. So say the lens is an 18-55mm. If at 18mm you have it wide open (at 3.5), and then zoom in to 55mm, it will remain wide open, but because of the limitations of that lens at 55mm wide open is now f5.6, so you are underexposing.

Better quality lenses will have a constant aperture. For example, if you see a similar lens but it says it's a 18-55mm f2.8, this means if you have it wide open at 18mm and then you zoom, it will stay at f2.8 and exposure will not change with focal length.

 

[SabrinaO]

You know your Aperture can change when you zoom, right? Did you check to see if that's what happened, because that's what it sounds like to me, although I'm sure someone will correct me if I'm wrong.

That's right but I shoot in manual so I don't think it would of changed on me. But maybe i just thought it happened. Im not 100% sure. I just thought I noticed it during the shoot when I was chimping.

I shoot manual too. It changes when you zoom if you're at the wide end of the aperture range.

Thats right! You are right! I remember now.. I remember it does change... I completely forgot about that. Thanks!

 

[SabrinaO]

Focal length on it's own does not change exposure, but as had been stated above, zooming often changes the aperture. If you have a basic lens, you'll see a number on it such as f3.5-5.6 This gives you the maximum aperture throughout the focal range. So say the lens is an 18-55mm. If at 18mm you have it wide open (at 3.5), and then zoom in to 55mm, it will remain wide open, but because of the limitations of that lens at 55mm wide open is now f5.6, so you are underexposing.

Better quality lenses will have a constant aperture. For example, if you see a similar lens but it says it's a 18-55mm f2.8, this means if you have it wide open at 18mm and then you zoom, it will stay at f2.8 and exposure will not change with focal length.

This is what made me remember. Thanks nikon dude! And thankyou everyone!

 

[Helen B]

Heres a comment what someone said in another forum...

Instead of shooting at such a high ISO, you could have resorted to a shorter focal length lens which lets you get closer to the subject and captured the same image at a lower ISO.

The inverse-square rule applying to on-camera fill flash sounds like it could be the reason here. (either that, or whoever wrote it was simply wrong - it happens occasionally on the internet) The variable aperture zoom explanation just doesn't ring true for me - ie it doesn't fit the sense of the comment.

Best,
Helen

 

[Robin Usagani]

You need to understand your camera metering. If you set your metering to evaluative metering for example. Lets say your photo has a lot of bright background. Zooming in to the subject and eliminating some of the bright background will change your metering. Since the camera sees more lower tones (since you are zoomed in), then it will expose your photo higher.

But this can happen both ways. Lets say your subject is lit up and the background is dark. The above situation will be reversed.


OR i completely missed your question.. maybe you have a lens that doesnt have a constant max aperture.

 

[Infidel]

Heres a comment what someone said in another forum...

Instead of shooting at such a high ISO, you could have resorted to a shorter focal length lens which lets you get closer to the subject and captured the same image at a lower ISO.

Shorter focal length can allow for good handheld results at slower shutter speed, thus lower ISO....

 

[Village Idiot]

Exposure changes when the subject moves farther or closer to a source of light.

That's that.

 

[Helen B]

Exposure changes when the subject moves farther or closer to a source of light.

That's that.

Exactly. I'm glad someone agrees with me.

Best,
Helen

 

[o hey tyler]

I don't know... Sounds like she's losing a stop of light from zooming in to me. For all we know, she could just be shooting in sunlight and not using popup flash.

OP- You could post two photos, one of the proper exposure, and one of the darker one (along with either embedded EXIF or copypasta'd)

 

[Derrel]

I had a shoot the other day and when I zoomed out the exposure was a little darker. I also just read a comment on DPF saying that if someone got a closer focal length they wouldn't have to use such a high ISO.

Well, let me take a shot at the first part of that statement:focal length can, and quite often DOES, affect light metering results. For instance, when a lens with a wide field of view is used, quite often a large expanse of sky can be included in the top part of the frame, and that can lead to "darker" exposures.

A narrower field of view lens, like say a 200mm lens, will not tend to be influenced by the sky when photographing things close to ground level. The disparity between a wide-angle lens and a telephoto lens's angle of view can very easily, and quite frequently, lead to very wide differences in light meter readings.

As far as what you read on DPF...I wouldn't put too much stock in that comment...