New 50mm 1.8 day for me!

Hey guys, just got this lens today. It is now my second lens and I am enjoying it!

One question though. I took a test shot on my pool table and I noticed something weird. To me at least!

There's a strip that is in focus on the carpet of the pool table. Is that normal? It's like everything before and after the 4 ball is out of focus, then where the 4 ball is, which is what was focused on, there is a strip that is in focus. Should it not just focus on the ball and throw everything else out of focus? Is this because the lens is cheap?

No, it's working the way it should.
The lens doesn't focus on a "spot", it focus across the field of view.From one side to the other.
Someone will surely explain this effect better than I.

Everything in the same plane as the 4 ball will be in focus.

Anything that is in the same focal plane as the ball will be in focus. Working on 3 planes lets call this the Z plane. There are 2 other planes X and Y (horizontal and vertical). If an object is in the same Z plane as the focus object (the ball) it will be in focus. Its position in the X and Y plane have no affect on whether it will be in focus.

huh, cool, thanks for the info. now what would be the correct way to shoot this? or is this acceptable?

Max Powers wrote in post #11635494
huh, cool, thanks for the info. now what would be the correct way to shoot this? or is this acceptable?

I just got mine last week as well. I know what you mean about that depth looking odd (with that part of the table in focus). Perhaps if you shot up at the ball, not capturing the table it may work. I think it mainly does this on horizontal surfaces. You don't really notice it in a shot where a person is standing at a specific distance away from you.

That's perfectly normal, and nothing to do with the cost of the lens. This is how one would expect it to look taken with a standard lens at a wide aperture. When you focus on something, and you're using a wide aperture like this, you get a focal plane at a fixed distance from the lens, and only things very close to that plane are in critical focus. The more you stop down, the greater the depth-of-field becomes (the range in front of and behind the focal plane where things appear in focus).

With standard prime lenses the focal plane is effectively flat and parallel to the sensor. Tilt-Shift lenses give you more control over where the focal plane is, allowing you to tilt it away from being parallel with the plane of the sensor.

DAMphyne wrote in post #11635408
No, it's working the way it should.
The lens doesn't focus on a "spot", it focus across the field of view.From one side to the other.
Someone will surely explain this effect better than I.

Thanks! I got the same lens and my photos came out blurry.

nice shot

2nd question added

1. The area of focus is a plane parallel with the sensor, so the strip of table should be in focus as would anything directly above it.

2. Star Lights are normal, I think aperture blades may change how they look slightly, but I am pretty sure most lenses gives some form of star shape.

A lens can focus on a plane that is perpendicular to itself. The larger the aperture, the thinner that plane becomes. So yes, when you focus on the ball, anything around it that is in the focus plane will be in focus.

As for the stars, this happens when shooting at large apertures with long exposures.

However, I have shot many long exposures with my 17-85 lens and haven't gotten that same effect. It's a pretty drastic difference when compared side by side.

EF-S 17-85

For the pool ball, that is because your depth of field is shallow. This blurs out everything in the rear and this happens when your aperture is big (smaller f-stop number)

The 50mm f/1.8 is composed of a 5-blade diaphragm so the starlight appears that way in long exposures.

ohericcc wrote in post #11638206
For the pool ball, that is because your depth of field is shallow. This blurs out everything in the rear and this happens when your aperture is big (smaller f-stop number)

The 50mm f/1.8 is composed of a 5-blade diaphragm so the starlight appears that way in long exposures.

For the ball, I know what the depth of field is. I was just wondering why there was a line of clearness with out of focus before it. It has been explained since though.


As for the lights, I realize that now. Well, this lens will have to stick to daytime and short exposure duty.

I can't stand the look of those star lights lol.