parallax problem with SLR lens on DSLR body

[schnuezel]

I have a kit lens that came with my EOS Rebel XS film SLR back in the 90s.  I've put it on the body of my EOS Rebel XS DSLR for my daughter to learn with.    We're finding that there is quite a bit of parallax which is difficult for her to compensate for as she's learning.  Any ideas why this is happening and if there's anything I can do about it?

[RobertTheFat]

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@schnuezel wrote:

I have a kit lens that came with my EOS Rebel XS film SLR back in the 90s.  I've put it on the body of my EOS Rebel XS DSLR for my daughter to learn with.    We're finding that there is quite a bit of parallax which is difficult for her to compensate for as she's learning.  Any ideas why this is happening and if there's anything I can do about it?

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Whatever you're experiencing, it isn't parallax. Since in any SLR you're looking through the same lens that takes the picture, parallax is, by definition, impossible.

That said, only the most recent and/or most expensive DSLRs show you a 100% view of the scene the camera will capture. Around the time of the XS it was, IIRC, somewhere in the low nineties. So you won't see as much as the camera sees, and there's nothing you can do about that. But it isn't parallax.

[Waddizzle]

I don't understand how parallax is an issue with a single lens.  What is she tryiing to photograph?

[kvbarkley]

As others have said, it ain't parallax. Parallax happens when the image from the non-imaging-lens viewfinder sees something different than the imaging lens.  Can you post some images that illustrate the problem?

[schnuezel]

Thanks, all.  Okay, it isn't parallax, but that's the best way I could describe it.  There is definitely an offset between what you see in the viewfinder and what you're actually taking a picture of.  When I was using the camera I was constantly cutting things off unless I intentially framed the picture differently from what I wanted to take a picture of.  It made it very difficult to use the camera.  I purchased the DSLR body used, and the gentleman I bought it from told me this would happen, but I can't for the life of me remember what he gave me as a reason.  I also never expected it to be so pronounced. 

[kvbarkley]

As pointed out, the viewfinder only shows about 90% of what the sensor sees.

You need to take some careful test images on a tripod to see what is going on.

If it is not just the framing difference between the viewfinder and the sensor, the only other thing I can think of is that the mirror is not going all the way into position when you are using the viewfinder.

Does this camera have liveview?

[ebiggs1]

"As pointed out, the viewfinder only shows about 90% of what the sensor sees."

What this means is some, possibly different on the top and bottom from the sides, is going to be "cut off".  There is nothing wrong.  This is how all DSLRs work if they don't have a 100% view finder.  It is also possible your film camera and the digital one have different viewfinders with different coverage.  This would cause the issue you are seeing.

I instruct all my 'students' to make sure you leave room around the outside of your subject for this type thing and later cropping in post.  For example, it is difficult to make an 8x10 of a digital image if the framing is too tight.  This is actually the same thing you are seeing.

Parallax error occurs in twin lens reflex cameras. For example, cameras which use a different optical system for the viewfinder and a different lens for image capture.

[RobertTheFat]

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@ebiggs1 wrote:

"As pointed out, the viewfinder only shows about 90% of what the sensor sees."

What this means is some, possibly different on the top and bottom from the sides, is going to be "cut off".  There is nothing wrong.  This is how all DSLRs work if they don't have a 100% view finder.  It is also possible your film camera and the digital one have different viewfinders with different coverage.  This would cause the issue you are seeing.

I instruct all my 'students' to make sure you leave room around the outside of your subject for this type thing and later cropping in post.  For example, it is difficult to make an 8x10 of a digital image if the framing is too tight.  This is actually the same thing you are seeing.

Parallax error occurs in twin lens reflex cameras. For example, cameras which use a different optical system for the viewfinder and a different lens for image capture.

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I agree with everything Ernie said except his statement that there's nothing wrong. If a viewfinder isn't going to give you 100% coverage, it should at least not show you more than you're going to get on any of the four sides. After all, the reason cheap DSLRs don't give you 100% coverage is to compensate for sloppy alignment of the viewfinder. In this case it's just too sloppy.

Low-end Canon DSLRs use mirrors instead of a prism in their viewfinders. Maybe one or more of the mirrors is out of position. Whether it could be fixed is hard to predict without opening it up. What's easier to say is that it's probably not worth the labor cost in such an old camera.

[schnuezel]

Interesting food for thought.  I get that the viewfinder doesn't show you exactly what the actual picture will be.  The camera doesn't have live view, so I can't use that.  I haven't tested the old lens on my Canon 70D.  I'm going to try that and report back.  If the problem is there too, then I know it's caused by the lens.

[Waddizzle]

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@schnuezel wrote:

Interesting food for thought.  I get that the viewfinder doesn't show you exactly what the actual picture will be.  The camera doesn't have live view, so I can't use that.  I haven't tested the old lens on my Canon 70D.  I'm going to try that and report back.  If the problem is there too, then I know it's caused by the lens.

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According to all of the documentation and reviews, the Rebel XS DSLR does have Live View.

https://www.usa.canon.com/internet/portal/us/home/support/details/cameras/support-dslr/eos-rebel-xs-...