7dII FOCUSING PROBLEMS WITH 300MM PRIME LENS

[East Wind Photography]

Just shows that if you're going to make emphatic statements, make sure you get it right.

No you don't have to get it right. You just need to accept the gauntlet of experts (both photographers and linguists) that will ensue on CR to attempt to belittle you into leaving.

It's ok to mis-speak as long as someone else clarifies to make it right. After all, that is why we are here, To get answers to questions and concepts that are not always fully and accurately understood.

 

[Lee Jay]

Yes it was kind of sloppy to say "when everything is equal" and not mention framing. In real life you want the same framing no matter what sensor size you use, but I should have included that info as well and not take for granted that everyone would understand that.

The reason we didn't understand that is that you said the opposite. You said, "If you have the same focal length, aperture and distance to the "object" you are photographing...". If those are all the case, you don't have the same framing. Regardless, it's wrong anyway.

Let's say you adjust one of your constants so that you do have the same framing. Let's use the logical one and adjust focal length by the crop factor.

100mm * 1.6 = 160mm.

7D, 100mm, f/2.8, 10 feet, DOF = 0.32 feet
5D, 160mm, f/2.8, 10 feet, DOF = 0.19 feet

Oops...not the same even with the same framing.

If you want DOF to be the same across formats, and you want to hold framing constant, have have to multiply both focal length and f-stop by the crop factor.

f/2.8 * 1.6 = f/4.5

7D, 100mm, f/2.8, 10 feet, DOF = 0.32 feet
5D, 160mm, f/4.5, 10 feet, DOF = 0.30 feet (the difference is caused by round-off error).

 

[serendipidy]

This is all so circle of confusing to many, including me. But I remember some people on this site have boiled it down to:
DOF depends only on true aperature size and image magnification (or something to that effect). Is that correct?

 

[Ruined]

I have both the 7D and the 7dii. I had the 7D for nearly a year and the 7Dii was supposed to be an upgrade for me.
Both cameras were set to the same exact settings (or as close as possible given that the shutter speeds have slight variations, etc.). I was shooting horse races using both the 70-200mm f/2.8 L IS II and the 3oomm f/2.8 L IS prime lens. On day one I used the 7D and 7Dii with the 70-200 lens alternating cameras one race after the other. On day two I alternated cameras race by race using the 300mm. RESULTS: Both the 7D and 7Dii shot identical quality shots using the 70-200mm. Using the 300mm prime lens, only the 7D shot in-focus shots one after the other. Nearly every shot taken by the 7dii was blurry. I spent a solid week testing and retesting. Same results.

There is something inherently wrong with here. Compatibility issues? Maybe? I sent the 7Dii back to B+H which honored their 30-day return policy.

Now my search for an upgrade to the 7D continues. I thought the 7Dii would be that upgrade but it turned out to be a huge disappointment!

Regardless of all the unrelated banter in this thread, I do believe a larger than usual number of 7D2 bodies were released with major autofocus problems. There are too many postings like this across many forums and Canon is replacing hardware in many cases to fix it or making hardware adjustments.