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Is 17-55 darker than other lenses?

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Smeicy

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I thought that f/5 at the same shutter speed would deliver the same result no matter what lens I am using on my D200.

I have just tested my 17-55 mm f/2.8 against my 50 mm f/1.8 and if I test them in the same setup and under identical light my 17-55 seems darker than my 50 mm. The shutter speeds were:

17-55 f/2.8 – 1/250 sec.
50 f/2.8 – 1/800 sec.

In another setup against my 18-200 VR I got the following results:

17-55 f/5 – 1/20 sec.
18-200 f/5 – 1/40 sec.
50 f/5 – 1/50 sec.

The light level in the pictures seems identical when shown on screen.
My f/2.8 is tack sharp wide open… is that because f/2.8 is not f/2.8?

Cheers
Smeicy
 
I had a feeling that this was not normal. The sorry part is that the lens just has been at my local Nikon Service Center for adjustment.

Perhaps the aperture blades are hanging or the lens need another adjustment.

Smeicy
 
Just did another test – and the following settings produce identical histograms at identical shutter speeds and lightning:

17-55 mm: f/2.8
50 mm: f/4.5
18-200 mm: f/4

No wonder my 17-55 is sharp at f/2.8.

Smeicy
 
Set the lens to f/2.8 and shutter to 1 second and look into the lens and see if the aperature closes at all when you release the shutter = if it does then it's back to Nikon.
 
Smeicy said:
I thought that f/5 at the same shutter speed would deliver the same
result no matter what lens I am using on my D200.

I have just tested my 17-55 mm f/2.8 against my 50 mm f/1.8 and if
I test them in the same setup and under identical light my 17-55
seems darker than my 50 mm. The shutter speeds were:

17-55 f/2.8 – 1/250 sec.
50 f/2.8 – 1/800 sec.

In another setup against my 18-200 VR I got the following results:

17-55 f/5 – 1/20 sec.
18-200 f/5 – 1/40 sec.
50 f/5 – 1/50 sec.

The light level in the pictures seems identical when shown on screen.
My f/2.8 is tack sharp wide open… is that because f/2.8 is not f/2.8?

Cheers
Smeicy
Click to expand...
Do a bit of research on "T-Stops". An f-stop is a numerical ratio of the iris diameter to the focal length of the lens. It is not a measurement (or guarantee) of the amount of light that will pass through the lens.

(Even a lens with a totally opaque front element can still be an f2.8 lens.. :> ).

= Dan =
 
I compared my 17-55 to my Tamron 17-50 the other day. Same focal length, f-stop, and shutter speed. The Nikon was darker by maybe 1/3 to 1/2 stop. Thought it might be that the Nikon was just more contrasty.
jk
 
Smeicy said:
Just did another test – and the following settings produce
identical histograms at identical shutter speeds and lightning:

17-55 mm: f/2.8
50 mm: f/4.5
18-200 mm: f/4

No wonder my 17-55 is sharp at f/2.8.

Smeicy
Click to expand...
I just compared the 17-55 against the 50mm f/1.8, and I get exactly the same shutter speed, aperture and histogram.

Something must be wrong with your lens. Before you take it back to Nikon, play with the aperture actuator on the bayonet mount of the lens. It should feel light and the aperture blades should close without delay when you release the actuator (just compare the feel with that of your 50mm f/1.8).
Also, carefully wipe clean the contact pins on the lens.

Rgds
Wilfried
 
After reading your thread out of sheer curiousity i tried what you did. The result was exactly as expected - the 50mm stopped down to f/2.8 yielded similar results then the 17-55DX @ 50mm @ f/2.8. Guess your 17-55DX need a check. HTH!

--
Cheers
Virgil
My snapshots: http://www.photoforum.ru/12675
Member of NPS
 
On modern coated / multi-coated lenses T-Stops and G-Spots won´t make a difference of 1-1½ stops as what the original poster found. A 17-55 probably has less and higher quality elements than a 18-200, ie. it should be the darkest of them all.

The best thing for checking things out is by shooting a grey card in fixed conditions with camera on manual and controlled lighting. Cheap flashes won´t do, as they vary in output much more than allowed for lens testing. A grey card also is a good tool for checking color differences on lenses.
 
I can't think why anyone would want to do this comparison between two or more lenses. Even more curious, I can't understand why you'd worry when there's a discrepancy. Surely in the rreal world, that's not how you take photographs.
--
JMS
http://www.photovue.co.uk
 
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