Let's talk exposure

[mill4023]

Ok I'm missing something people keep saying the settings are off for such a bright day, was it a really bright day or do the pics just appear that way because of a stuck wide open aperture...


I bought a 50mm 1.7 minolta lens off of craigslist 2 years ago, I actually got 2 7000 maxxums plus the lens for 50 bucks, so I took the stuff and left, got back to my office, popped the lens on one of my A700s and started taking pics, the pics were all over exposed, I switched to full manual and the pics were still overexposed no matter what aperture setting I used..

so at least in my case a lens error did not occur

what if the aperture is sticking and the exif is actually captured at the moment of exposure so it's showing the lens open more than the meter would have chosen

It was a sunny day, probably around noon or 1pm.

I also was wondering if the EXIF data was based on what the camera told the lens to do or what the lens actually did. There is obviously some data that the camera reads from the lens, like the focal length, so maybe the camera is reading the aperture data from the lens also.

I will have to do some more thorough testing to be sure, but I don't think I was having the same problem with my 70-300 VR.

This picture is the most severe example of the corner darkness that made me think it was a lens issue.
http://s-miller.smugmug.com/Photography/Overexposed/14665060_Xadoi#1092492077_cTCSK-A-LB

 

[MICKEY88]

I will have to do some more thorough testing to be sure, but I don't think I was having the same problem with my 70-300 VR.

This picture is the most severe example of the corner darkness that made me think it was a lens issue.
http://s-miller.smugmug.com/Photography/Overexposed/14665060_Xadoi#1092492077_cTCSK-A-LB

thorough testing will work, but it's really as simple as doing what Code or I suggested earlier, that will tell if it's the aperture sticking

 

[GrillMouster]

Prior to the shutter being released, the lens' aperture is supposed to be at its widest possible setting, so the maximum light possible can enter the camera for autofocus and metering. If the aperture were stuck stopped down, it could fool the camera's meter into thinking that the scene is darker than it truly is. That could explain why the images have shutter speeds that are a few stops too slow for the conditions. That could also be one reason for the corner vignette on some images, but not others. (if it was caused by a filter or lens hood, all the images taken at 18mm would have the same vignette, and it would be uniform on all four corners, not just heavy on the upper left).

Anyway, you said that you don't get this problem with the other lenses, so I think this lens is bad.

 

[mill4023]

Prior to the shutter being released, the lens' aperture is supposed to be at its widest possible setting, so the maximum light possible can enter the camera for autofocus and metering. If the aperture were stuck stopped down, it could fool the camera's meter into thinking that the scene is darker than it truly is. That could explain why the images have shutter speeds that are a few stops too slow for the conditions. That could also be one reason for the corner vignette on some images, but not others. (if it was caused by a filter or lens hood, all the images taken at 18mm would have the same vignette, and it would be uniform on all four corners, not just heavy on the upper left).

Anyway, you said that you don't get this problem with the other lenses, so I think this lens is bad.

No filters. No lens hood.
I don't think I have this problem with other lenses, but I can't be sure that I've taken pics in similar bright conditions.

I will follow some of the suggestions that have been made when I get a chance.

 

[mill4023]

OK. I followed the suggestions of Code and Mickey88

1. Putting it in A mode and f/22, I pushed the depth of field preview button and it sounded like the aperture was closing, but I didn't notice any change in the viewfinder and I wasn't sure what else to look for.

2. I put it in manual mode and set to 1/60 and ISO 400. I took a series of pics from f/3.5 to f/22. They all look the same to me. Here are the pics from that test:
http://s-miller.smugmug.com/Photography/TestShots/14687047_zhLBT


Before I clicked Submit on this post, I figured I'd do the same tests with my 50/1.8. Night and day difference. Now I know exactly what I was looking for. With test 1, it gets much darker in the viewfinder when pressing the DOF button. With test 2, I can clearly see the progression from lighter to darker pictures as the aperture gets changed.

So it's definitely the lens, which is good I guess.
Don't all the Nikon lenses have a 5 year warranty?

Thanks for everyone's help.

 

[photo_chick]

If anything it looks brighter at f/22. Wow... learn something new every day. I would not have gone to the aperture.

 

[mill4023]

The thing I still don't understand is why the EXIF data in my test shots is showing the aperture I set it to, while the original outdoor shots I took appear to be showing the aperture that the shot ended up with, rather than what the camera should have been telling the lens to do.
I wonder if it behaves differently (in terms of getting EXIF) when it's in manual mode vs automatic.

 

[GrillMouster]

The EXIF is showing what the camera body thinks the aperture was. Unfortunately, because the aperture in the lens is wonky, the aperture actually used is different than what the body thinks it was.

The depth of field in the original outdoor images lead me to believe that the aperture in the lens was stopped down more than what it says in the EXIF data. Those images are overexposed because the shutter speed is slow for the light levels. (because the aperture is stuck stopped down, the meter was fooled into thinking the scene was darker than it really was, and so it selected a slow shutter speed).

So, In both the original and in your more recent test, the aperture showing in the EXIF data is what you (in manual) or the camera's meter (in automatic) set it to, but in reality the lens' aperture did its own thing.

 

[materise]

just atarted a class nut have the nikon 500 now