Why is my lens 'brighter'

Ady N

Ady N

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Not sure if that is the correct term but I have had a Nikon 300m f/4 for a few years and used it today for the 1st time in a while. I have always noted that exposures with this lens are brighter than with any other lens I own and sometimes I have to dial in negative compensation whereas I usually dial in +.25 for my 70-200 when doing sports stuff.

I suppose my question is why would this be?

Typically I shoot on aperture priority with auto ISO set to sustain a minimum shutter speed I require for what I am shooting.

Thanks.
 
I have one lens that does this too. Do you know if the aperture iris is closing quickly enough? Having oil on the blades can slow it closing and cause this effect.
 
It's done it from new - that's about all I can say really. It's not an issue, I just have to remember when I stick it on the camera, just interested in why really.
 
Ady N said:
It's done it from new - that's about all I can say really. It's not an issue, I just have to remember when I stick it on the camera, just interested in why really.
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The hole in th lens is not closing properly.
 
Ady N said:
It's done it from new - that's about all I can say really. It's not an issue, I just have to remember when I stick it on the camera, just interested in why really.
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Yeah I think it's what the other posters are describing, I just had a Sigma 105mm with the same issue, it was absolutely mint and seemed like a perfect copy but it'd over-expose by about half a stop depending on the aperture setting.

I could see the fault in action by just adjusting the aperture setting and pressing the DOF preview button, between (I think) f/3 and f/3.5 the aperture didn't get any smaller while on another copy of the lens it worked as expected.
 
I had this on my Sigma 70-200 on my Canon 50d, but on my 6d its normal, could never figure why? From what I can see the aperture is working perfectly?
 
odd jim said:
I had this on my Sigma 70-200 on my Canon 50d, but on my 6d its normal, could never figure why? From what I can see the aperture is working perfectly?
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It's easier to tell if you have another copy of the same lens and can test each step but that's assuming you have exactly the same problem as I did, on mine it literally missed a step but you might have a similar yet still distinct issue causing the same result.
 
You should google T-Stops which is in essence the amount of light that a lens transmits from the front element to the camera sensor. If 2 lenses (different models) have the same F-STOP the T-STOP can be massively different.

In fact Tony N. has just released a video expling it far better than I can ....

View: https://www.youtube.com/watch?v=YF-VJpePTIY&feature=youtu.be&a
 
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The F number is just a representation of the physical size of the aperture in relation to the focal length - if all lenses were made the same with the same glass and arrangement of elements, they'd all be equally bright at the same apertures. They definitely aren't, and it's one thing which tends to separate cheap lenses from expensive ones, sometimes very noticeably.
 
There's also the question of whether the apertures are correctly marked. Admittedly some years ago, and on large format lenses, but Ansel Adams did find some large inaccuracies of marking that lead him to recalibrate his lenses. You say you use aperture priority; always the same aperture stop? And if so, what? Not that it would mean anything to me, but it's extra information "just in case".
 
A few posters need to go back & read the OP again. ;)
 
Geoff Moore said:
You should google T-Stops which is in essence the amount of light that a lens transmits from the front element to the camera sensor. If 2 lenses (different models) have the same F-STOP the T-STOP can be massively different.

In fact Tony N. has just released a video expling it far better than I can ....

View: https://www.youtube.com/watch?v=YF-VJpePTIY&feature=youtu.be&a
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Thanks for this - it's a whole new thing I didn't know about (and will now probably worry about)!
:-)
 
Lens transmission (T-stop) has zero affect as far as requiring exposure compensation... the meter uses the light that is transmitted (after losses) when determining exposure.

Since it's always done it, and it seems to be consistent across all apertures, I would say it's a calibration issue rather than an aperture malfunction as such.
 
sk66 said:
Lens transmission (T-stop) has zero affect as far as requiring exposure compensation... the meter uses the light that is transmitted (after losses) when determining exposure.

Since it's always done it, and it seems to be consistent across all apertures, I would say it's a calibration issue rather than an aperture malfunction as such.
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I agree that this sounds like a calibration issue, but there can be exposure errors even though the light coming through the lens for metering is inherently adjusted automatically for transmission.

Metering is done with the lens wide open when vignetting is most prominent and this can both upset the meter and also makes images taken with the lens closed down (and vignetting sometimes dramatically reduced) appear brighter even when the exposure is technically the same. And lens aperture settings are not always accurate, and can also be inconsistent particularly at high f/numbers when small mechanical errors translate into significant aperture changes. Rarely anything to worry about though.

I have a lot of time for Tony Northrup and while he makes a valid point in his video linked above, he has over-egged the problem. He often uses DxO as a source for his references but DxO's T/stop figures are not reliable, and neither are their focal length measures.
 
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