Stupid focus question...but hey...I need some friggin advice...

[charlie76]

Ok...I need advice on something please! Lately I have been shooting wood compositions (some of you probably have seen, I've been at if for a few weeks now)...I am struggling with focus in the entire frame...and I need a little advice from the gurus...and try not to make too many smart-A comments if this is a stupid question

Try to stay with me while I explain:

Consider a flat subject...looking straight down at beach sand, for instance. I want to shoot it from 2-3-4-5-6 feet away....with a zoom lens...50-100mm (that's the best "zoom" I have). Now here comes the stupid question. With large apertures...crisp, clear focus...but only in the center of the frame. The rest is blurry as hell. Small apertures...not crisp...but the same in most areas of the frame

Using f-9 or f-10....gives ok focus on "most" of the frame...and good crispness in the center.

Am I thinking about this the right way? How can I get the entire frame as sharp as the center when using large apertures??

 

[Ernicus]

I put a link up to a dof calculator in your other thread. I'm guessing you are too close, so being that close you'll have to stop down more and in return need more lighting. When you are really close...you only have a few inches of dof, resulting in areas of your subject out of focus.

 

[Ernicus]

plugging in your info from a shot of yours I have, you can see your total dof is .56 ft or basically 6 inches. That's guessing at 5 feet away.

Online Depth of Field Calculator

 

[Ernicus]

also, were you shooting free hand? or on a tripod? does your zoom have VR?

 

[charlie76]

plugging in your info from a shot of yours I have, you can see your total dof is .56 ft or basically 6 inches. That's guessing at 5 feet away.

Online Depth of Field Calculator

Ah..I see. That's what I thought. I haven't taken this many close shots..and never had to "focus" on this issue before...lol

 

[charlie76]

also, were you shooting free hand? or on a tripod? does your zoom have VR?

freehand...and yes, my lens has VR...which I leave on. Never used VR in any of my older film stuff...I think it is some sort of vibration reduces (VR)...does it mess with focus or anything? Should I leave it off?

 

[480sparky39 38]

also, were you shooting free hand? or on a tripod? does your zoom have VR?

freehand...and yes, my lens has VR...which I leave on. Never used VR in any of my older film stuff...I think it is some sort of vibration reduces (VR)...does it mess with focus or anything? Should I leave it off?

Nikon VR explained.

 

[charlie76]

Nikon VR explained.

Thanks Sparky.....Im on it.

 

[Ernicus]

There are many reads on it, sparky put a good one. My personal experience with it , on a 70-300mm VR. I loved it. Freehand, I sucked so bad. Just was not used to the lens, with practice I would have gotten better. I was able to get an airplane in flight at 300mm, in focus. So I loved the VR on that one. It is noisy..but thats normal.

on the 55-200mm vr....didn't reach out and touch me as much. It was ok...but I did ok without it.

on my kit lens..I hardly use it.

I never use it on a tripod...it can actually throw of your line of sight as it can cause a bit of barrel move...so program in your brain to turn it off when on a tripod.

Just my personal observations on 3 lenses with it. Hope it helps.

oh...one thing you might notice, especially at longer focal lenghts...if you move to get something quick you see off to the side or something, you may notice some lag in the image in your viewfinder "catching up" to your eyesight....that's normal.

 

[charlie76]

There are many reads on it, sparky put a good one. My personal experience with it , on a 70-300mm VR. I loved it. Freehand, I sucked so bad. Just was not used to the lens, with practice I would have gotten better. I was able to get an airplane in flight at 300mm, in focus. So I loved the VR on that one. It is noisy..but thats normal.

on the 55-200mm vr....didn't reach out and touch me as much. It was ok...but I did ok without it.

on my kit lens..I hardly use it.

I never use it on a tripod...it can actually throw of your line of sight as it can cause a bit of barrel move...so program in your brain to turn it off when on a tripod.

Just my personal observations on 3 lenses with it. Hope it helps.

oh...one thing you might notice, especially at longer focal lenghts...if you move to get something quick you see off to the side or something, you may notice some lag in the image in your viewfinder "catching up" to your eyesight....that's normal.

That is good insight..thanks Ernie

 

[Bitter Jeweler]

Are you absolutely, positively, sure your your focal plane is absolutely parallel to the subject?
With shallow DoF, not being parallel could make your edges softer and your center crisply focused, because the edges are falling out of the plane of focused DoF.

 

[charlie76]

Are you absolutely, positively, sure your your focal plane is absolutely parallel to the subject?
With shallow DoF, not being parallel could make your edges softer and your center crisply focused, because the edges are falling out of the plane of focused DoF.

Good point...I think about that sometimes and vary my angle slightly when shooting. I'll consider that more often when I'm shooting these types of shots.

 

[SoCalTiger]

Are you absolutely, positively, sure your your focal plane is absolutely parallel to the subject?
With shallow DoF, not being parallel could make your edges softer and your center crisply focused, because the edges are falling out of the plane of focused DoF.

Good point...I think about that sometimes and vary my angle slightly when shooting. I'll consider that more often when I'm shooting these types of shots.

Yeah this was my thought too. If you're not totally in line with the focal plane that would cause apparently loss of clarity toward the edges. Aside from that, most lenses do have some loss of clarity towards the edges... varying depending upon the specific lens. There are some example shots here to give you an idea:
Review of the Canon EF 40mm f/2.8 STM lens (page 2) - LENSTESTS

Expand the "Test Shots" link under the "Sharpness/Resolution" section.

 

[KmH]

You are also dealing with field curvature (focus plane curvature).

In an ideal world a lens delivers a flat field, but because lens elements vary in thickness form the edge to the middle of the lens they deliver a curved field of view.

 

[charlie76]

You are also dealing with field curvature (focus plane curvature).

In an ideal world a lens delivers a flat field, but because lens elements vary in thickness form the edge to the middle of the lens they deliver a curved field of view.

I'm glad I started this thread. Better understanding of the hardware = less guess work = better control of the image