possible 5100 related problem

[Slipperman]

why am i not getting an obvious difference in background blur even with high and low end aperture values??

35mm, iso 100, 1/2.5, f32


35mm, iso 100, 1/125, f5


this has been happening since i learned how to really use the camera (exposure). i suspect it could also be the lens. it's the standard 18-55 kit lens.

 

[Scott Murray]

How close are you to the grave stone? Sometimes distance to the foreground subject can affect the outcome (I have found anyway).

 

[Rick M]

f5 with a 35mm lens is still going to give you a lot of DoF. You will need to be close to the subject and probably be at f2.8 or lower to get oof elements at such a short focal length, especially on a Dx sensor.

 

[nickt]

Your camera and lens are good, your shutter speed slowed down as you f stop went up, keeping a good exposure. Here is something to play with. Online Depth of Field Calculator
Plug some numbers in and see how the dof changes at different focal lengths and subject distance. Blurry background will show up more when subject is fairly close and background is more distant.

 

[Horoscope Fish]

Because focal length affects depth of field.

The shorter the focal length, the deeper of the depth of field at the same aperture.
The longer the focal length, the shallower the depth of field at same aperture.

 

[Slipperman]

actually i was only like 3.5-4 ft away from that gravestone. i also had the focus mode set to auto and changed the area mode to single so i could choose the leftmost focus point out of the 11 and focus on the right side of the stone. i used to use auto area but that would have tried to focus on multiple points including the background which i didn't want.

also, f5 is the lowest aperture i can get on my lens at least in M or AP mode. maybe i should find a background that's a little further away.

 

[nickt]

I think the background is as blurry as its going to get in both shots. That is why no real difference. Your lens is focusing wide open, so what you see in the viewfinder is as blurry as its ever going to be. The background in the final image may be more in focus depending on the actual f-stop shot, but you will never get more blur than you see in the viewfinder. Try the shot at 55mm and back up from the stone a little bit. You might get more background blur that way.
Just to clarify, if you are shooting at f32, your actual dof will be greater (more stuff in focus) than what you see in the viewfinder. I don't know off-hand if the d5100 has a depth of field preview feature. A DOF preview stops the lens down so you can see through the viewfinder what the actual dof will be.

 

[urquel]

To me, the second has more blur in the background. Look at the lettering on the stone by the fence.

 

[Slipperman]

To me, the second has more blur in the background. Look at the lettering on the stone by the fence.

i did. but the difference is negligible. everything else looks about the same including the trees.

 

[Marcel]

Your f32 shot seems to be softer than the other one. I suspect that you might have run into the "diffraction factor". It's been reported that after going to f-stops smaller than f-16, some cameras show signs of diffraction making the subject softer than with an, let's say f-8 aperture. I think this is why the out of focusness (allow me to invent this word) seems to be the same for both shots. Where you using a tripod? And even with a tripod, sometimes one has to use the "mirror up" mode in order to remove the mirror slap vibration out of the equation.

Don't worry too much, sharpness is only one element of a great picture. Just take more and enjoy photography, not pixel peeping on the computer.

 

[Rick M]

Here's a couple examples I shot with my 35mm 1.4 lens. At 35mm, you need a really wide aperture. The first is at f5 and the second at f1.4,

 

[Slipperman]

2 more from today. different headstone that i was 5-6' back from, same focus, fence further in the background, same non-difference..

55mm, iso 125, 1/640, f5.6


55mm, iso 125, 1/10, f36

 

[Slipperman]

Here's a couple examples I shot with my 35mm 1.4 lens. At 35mm, you need a really wide aperture. The first is at f5 and the second at f1.4,

yeah, it's my lens - not a low enough aperture number.