70-200 f4 not performing great

[mommyof4qteez]

I upgraded months ago to a 5d mark ii and was super excited to try out my 70-200 f4 on the full frame...was very disappointed... it seems to perform better on a rebel...anyone else ever have this problem?

 

[fjrabon]

how is its performance lagging?

 

[Big Mike]

You will have to give us more info that that.

One thing to consider is that pretty much all lenses are sharpest & give the best quality in the centre of the image. Poor quality lenses will tend to drop of dramatically at the edges, while a better lens will drop off only a little at the edges. So when you use an EF lens on a crop sensor camera like a Rebel, you are only recording the middle section of what the lens is seeing...thus you are cropping off the edges where the quality may not be as good. So while you won't necessarily get better image quality with a crop camera, you probably get better edge to edge sharpness and consistency.

Another issue may be your DOF. When using a full frame camera, you get a shallower DOF when compared to similar situations with a crop camera. This shallower DOF means you have to be more precise with your focusing.

 

[ronlane]

You will have to give us more info that that.

Another issue may be your DOF. When using a full frame camera, you get a shallower DOF when compared to similar situations with a crop camera. This shallower DOF means you have to be more precise with your focusing.

So Mike, when you move from a crop to a FF, do you need to go up an f-stop or two for DOF, all things being the same? That will cause other issues with exposure won't it? How do you compensate for this difference?

 

[KmH]

Plus, on the FF camera there is no crop factor so you're seeing a larger FOV which looks like lens is delivering less magnification.

Ron, you can plug numbers into an online DoF calculator to get a sense of how the DoF changes with image sensor size. Online Depth of Field Calculator

Since the FF camera gives a wider FoV (field-of-view) for the same focal length, compared to a crop sensor body, the photographer will generally be closer to the subject to maintain subject scale in the image frame.

So as focal length and point of focus distance changes, the amount of lens aperture change will be variable. Compensate for the change in exposure using the camera's built in light meter.

 

[o hey tyler]

So Mike, when you move from a crop to a FF, do you need to go up an f-stop or two for DOF, all things being the same? That will cause other issues with exposure won't it? How do you compensate for this difference?

That would depend on your subject to focal plane distance as well as the DOF you require for the shot. You can get closer and maintain the same subject framing on a full frame camera than you can with a crop frame. Hence a shallower depth of field with the same lens, aperture and subject framing.

You would compensate for any exposure differences caused by stopping down your lens by either making the shutter speed longer or turning your ISO up.

Also, as far as the OPs query... Lens shortcomings are more apparent on a full frame due to the larger image capture circle and the way optics generally loose sharpness significantly on the edges (depending on the lens, focal length, and aperture.)

Wow. I posted a helpful response on TPF. Didn't think I'd do that again.

 

[JAC526]

I have not seen any issues with my copy. I'm shooting it on a 5dc.

 

[ronlane]

So Mike, when you move from a crop to a FF, do you need to go up an f-stop or two for DOF, all things being the same? That will cause other issues with exposure won't it? How do you compensate for this difference?

That would depend on your subject to focal plane distance as well as the DOF you require for the shot. You can get closer and maintain the same subject framing on a full frame camera than you can with a crop frame. Hence a shallower depth of field with the same lens, aperture and subject framing.

You would compensate for any exposure differences caused by stopping down your lens by either making the shutter speed longer or turning your ISO up.

Also, as far as the OPs query... Lens shortcomings are more apparent on a full frame due to the larger image capture circle and the way optics generally loose sharpness significantly on the edges (depending on the lens, focal length, and aperture.)

Wow. I posted a helpful response on TPF. Didn't think I'd do that again.

hey Tyler, thanks for the explanation. Sorry to break up your streak there.

 

[mommyof4qteez]

Just not near as sharp on my 5d as on my rebel... this makes so much sense!! Thanks a ton!!

 

[JAC526]

I'm pretty sure this lens was made for full frame cameras. I find it hard to believe that it is less sharp on full frame than crop sensor. I could see maybe less sharpness in the corners but overall I'm not so sure.

 

[ronlane]

You can send it to me, I have a crop

 

[Overread]

Few thoughts to add:

1) Increased frame size as been mentioned, but also remember that increased MP values between two cameras also means that comparing 100% crops between different cameras can show significant variation in sharpness. This generally shows that the 100% crop from a larger mp camera body is softer than that from a smaller one. This doesn't mean more MP is bad or that less is better, what it does mean is that larger MP sensors mean that a 100% crop is significantly larger in size - and as a result can appear softer; where as comparing at the same size (eg on a resize or a print) gives you a better idea of the comparison between the bodies.

2) Calibration. Each camera and lens is only made within manufacture tolerances and most aims for the middle ground; however you can get those which are a bit more to one end than the other. Normally this hardly shows up - however if you get a lens and a body which are at opposite ends the specific combo of that body and that lens can give a lesser level of image quality than expected, even though the body might well work fine with other lenses.
This is why you have the option to send lenses+bodies in for recalibration - however it should be noted that if you don't send both parts in recalibration of a lens is a lottery (since nothing is actually wrong with the lens its hard for the testers to "fix" the problem). You can, of course, send your camera bodies and lenses all in for recalibration - although you should note that you can't, of course, send in any 3rd party items.