Technical question re: lens

runnergirl · Oct 6, 2012

I have a Sony alpha 200 DSLR with a kit lens. I recently purchased the Sony alpha 50mm F1.8 lens and I have enjoyed the ability to set the fstop lower, but I have been having a strange issue. When I frame a photo in my viewfinder, focus and take the shot, the picture I get is not what I framed. Instead it seems to cut off the top and one of the sides. Yesterday I took some pictures of my baby and had to try to compensate by framing it in the viewfinder to have a lot of extra room at the top so that it wouldn't cut off the top of his head. Does anyone know why this would happen? Is something wrong with the new lens? Here is an example - I framed this photo to have my son's whole head in it, and it cut off the top. I still like the photo but would appreciate any ideas of what's wrong?

jaomul · Oct 6, 2012

Strange. Are you by any chance using a lens made for a 4/3rd type camera with an adapter? It seems like the lens rectangle is somehow designed for a smaller sensor than the one on you sony? Sorry if this is no help.
Actually that cannot be correct if this was the case you would just get vignetting (I should have kept quiet on this one:blushing:

runnergirl · Oct 6, 2012

Hmmm no, I mean the lens I bought is made for my camera model... Maybe I should call Sony or visit my local camera store

Kolia · Oct 6, 2012

Do you have the option of changing the aspect ratio of your pictures on the a200 ?

Kolia · Oct 6, 2012

And you don't get the same results with your other lens ?

Kolia · Oct 6, 2012

I'll take a wild guess and suggest you have some dirt in the camera that prevents the mirror to go all the way down while you are framing the picture.

unpopular · Oct 6, 2012

If that were the focus distance to the focus screen would be skewed, causing the lower half of the viewfinder to be significantly out of focus. Mirror misalignment may be the culprit, but does not explain why it would happen on this lens alone. If there is no abnormal focus, then I don't think that this is the case. I'm also not 100% sure, but the way I'm visualizing it, then the crop would also be on the bottom, not the top?

OTOH, I can't think of what else would be causing this.

Kolia · Oct 6, 2012

mirror up will show more of the top of the image in the view finder, causing her to shoot too high. (not convinced the image inversion applies there)

I don't know what else it could be.

KmH · Oct 6, 2012

The a200 specifications for the viewfinder say it only shows 95% of the actual image frame, and the magnification is only x0.83.

Kolia · Oct 6, 2012

KmH said:
The a200 specifications for the viewfinder say it only shows 95% of the actual image frame, and the magnification is only x0.83.

So her resulting images should show even more, not less.

unpopular · Oct 6, 2012

^^ yep. It may be worth pointing out that 0.83x refers to when there is a 50mm lens attached. When a wider lens is attached, the magnification is lower and the subject will appear smaller, when a longer lens is attached, the magnification is higher and the subject will appear larger as compared to the eye.

I don't know if that has anything to do with the problem.

runnergirl · Oct 6, 2012

Yes, this only happens with the new lens not the kit lens. I haven't changed the aspect ratio. Not sure about dirt on the mirror but wouldn't that affect both lenses?

unpopular · Oct 6, 2012

Yes. It would. But this problem is going to be most noticeable only at close focus. Still, I think that while this is the most likely problem, it is also very, very unlikely for the reasons I've stated. A small misalignment behind the lens has HUGE impact on sharpness. I think you'd have seen this, though I could be over estimating by how much.

Frankly though, having the viewfinder be affected with one lens but not the other just is not possible, unless the lens itself is somehow preventing the mirror from falling back completely; this does not seem likely... The lens and the viewfinder are separate optical systems; you could put a potato in front on your camera and it wouldn't affect the viewfinder. So I am just not understanding this at all.

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Hold on a second! Try turning off in-camera IS (SuperSteady Shot). I am curious if the sensor is getting stuck in one position. The IS and the lens are inter-related in mysterious ways, so maybe if the lens is defective, it is somehow sending a mad message (lol, I like that typo better) to the IS?

Before doing this, reset the camera by turning off IS, turning off the camera, removing the lens, removing the battery replace, replace the battery, replace with the lens you know works, test again, turn off, replace with the 50mm suspect lens with IS off.

IS in older sony cameras may also be just be a bit laggy. What shutter speed did you use here?

DiskoJoe · Oct 8, 2012

your probably using the 16x9 orientation instead of 3x2. Look it up in the menu. Im fairly certain this is correct when viewing the image. You can always tell when they are really wide as this image is.