is the depth of field suppose to be subtle?

ph0toe

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comparing these two photos i took with relatively same settings

environment, in doors, key light source window with shades/blinds and a lamp


manual mode
iso-800
shutter speed to 1/30 of a second
tried it with f 4.0 (lowest aperture) vs f 11 which most people take photo of product photography

i noticed the blurred in the background but not enough to make it very noticeable. why?

also, how can i angle the light to make the main subject glasses, be well lit and professional? obviously i will remove the stuff in background as it is distracting but i figured the f stop would blur all of it away so i didn't have to.

granted, i am not on tripod, but i do have the kit lense which has image stablization

ALSO, why is it that whenever i zoom in that is where my focus GOES. like for instance if i zoom to say 35mm, it will be blurry, but when i zoom back to 70mm i get a clear view ? i thought focus ring suppose to handle that but whenever i turn the focus ring it doesn't do anything.
help!
 

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Braineack

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Welcome to photography...
 

flyingPhoto

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Well as I am in a rather snarky mood, and the OP here has in a good number of posts, proclaimed 'a professional understanding of photography", ima gonna have some FUUNN

1. FOCAL LENGTH..... you have what we in the "know" call a ZOOM LENS. That means that it lets you change the focal length of the lens

2. Focal length, a longer focal length means the camera lens will see something farther away on a narrower cone of view, hence the roof top chicken you see at 35mm will be alot smaller then when you switch to 75mm or 100 and so on. The camera sees MORE because it is seeing a smaller circle/field at that magnification

3. YOUR CAMERA or LENS ISNT ON MANUAL... if the focus ring turns and the lens dont do ****,,,, you have what we call a settings error or a defective user to qoute the 1994 Computers for Dummies book.

to have manual lens control.... the camera MAY NEED to be on MANUAL MODE and the LENS itself may need to be turned to MANUAL ONLY MODE, or MANUAL OVERRIDE on mode

4. Focus, the lens has to REFOCUS ANYTIME it CHANGES FOCAL LENGTH

5. Image Stabilizer mode HAS TO BE TURNED ON INSIDE A CAMERA MENU FOR MOST LENSES
 

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With depth of field the distance between the subject and the background matters, if you want more blur, make the subject to background distance larger. Using a longer focal length can help as well.
 

AlanKlein

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I once read that it's smart to re-focus when you zoom. Many cameras don't hold the focus when they zoom.

What do you mean the focus ring doesn't change anything? Maybe there a setting you missed in the Menu that disables this?
 

smoke665

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noticed the blurred in the background but not enough to make it very noticeable. why?
On every lens there is an absolute plane of focus that is the sharpest point the lens will focus to. From that focal plane the area in focus will gradually diminish both in front of and behind the focal plane, that's called the DOF. Depth of Field (DOF) is a variable that is a function of Aperture, distance from the subject, and acceptable Circle of Confusion. Photographers use this knowledge to calculate the DOF they need for a particular image, using the formula:
dof.png


Or you can use one of the online calculators like - Online Depth of Field Calculator

ALSO, why is it that whenever i zoom in that is where my focus GOES. like for instance if i zoom to say 35mm, it will be blurry, but when i zoom back to 70mm i get a clear view ?

When it comes to focus, not all Zooms are equal, even by the same manufacturer. There are "Parafocal" a lens that stays in focus when magnification/focal length is changed and "Varifocal" a lens where focus changes as focal length changes. In my Pentax collection I have both, but mostly "Parafocal". There are various list out there on the internet that can tell you which are which, or as you determined it's easy to tell by use. Using manual focus in live view negates any change regardless of the lens type.

i do have the kit lense which has image stablization

Which camera do you have???? On Pentax and Sony the stabilization is in camera, something I prefer. I can leave stabilization on all the time without issue, unlike lens stabilizing.
 

stevet1

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comparing these two photos i took with relatively same settings

environment, in doors, key light source window with shades/blinds and a lamp


manual mode
iso-800
shutter speed to 1/30 of a second
tried it with f 4.0 (lowest aperture) vs f 11 which most people take photo of product photography

i noticed the blurred in the background but not enough to make it very noticeable. why?

also, how can i angle the light to make the main subject glasses, be well lit and professional? obviously i will remove the stuff in background as it is distracting but i figured the f stop would blur all of it away so i didn't have to.

granted, i am not on tripod, but i do have the kit lense which has image stablization

ALSO, why is it that whenever i zoom in that is where my focus GOES. like for instance if i zoom to say 35mm, it will be blurry, but when i zoom back to 70mm i get a clear view ? i thought focus ring suppose to handle that but whenever i turn the focus ring it doesn't do anything.
help!
ph0toe,

You have to flip the switch on the lens itself to manual. If you leave it on AF, you have to half press the shutter button and hold it there while you turn your focus ring, or hold the back button focus down while you turn the focus ring (assuming you have an electronic assist lens).

Assuming you are in single shot mode, if you pressed the focus button at 70mm and then released it, the focus will stay there until you press it again. If you change the focal length to 35mm, your picture will go out of focus until you go back to 70mm. If you want to focus at 35mm, you have to hit the focus button again.
If you are in Servo mode, and hold the focus button continuously, the camera will focus as you move the camera around.

If you want the background to be more blurry, you have to increase the distance between your subject and the background.

Steve Thomas
 

unpopular

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Now … if you live in places like California, Washington, Colorado or Canada try to imagine how a a lens with an infinite aperture or a focal length of zero would behave …
 
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ph0toe

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canon camera and once switch to image stablization
 

RAZKY

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comparing these two photos i took with relatively same settings environment, in doors, key light source window with shades/blinds and a lamp
manual mode
iso-800
shutter speed to 1/30 of a second
tried it with f 4.0 (lowest aperture) vs f 11 which most people take photo of product photography
i noticed the blurred in the background but not enough to make it very noticeable. why?

!
 
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RAZKY

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As long as you’re photographing the same subject size, your depth of field at any given aperture will be the same no matter what focal length lens you use. You’ll be in closer with a shorter lens and farther back with a longer lens.


I like this calculator:

 

RAZKY

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As long as you’re photographing the same subject size, your depth of field at any given aperture will be the same no matter what focal length lens you use. You’ll be in closer with a shorter lens and farther back with a longer lens.


I like this calculator:


Edit: Not sure why I didn’t get my comment to quote in the original post. Probably reply didn't take. My apologies for the multiple posts.
 
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Ysarex

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As long as you’re photographing the same subject size, your depth of field at any given aperture will be the same no matter what focal length lens you use. You’ll be in closer with a shorter lens and farther back with a longer lens.


I like this calculator:


Edit: Not sure why I didn’t get my comment to quote in the original post. Probably reply didn't take. My apologies for the multiple posts.

This is incorrect. It's a common myth that you can factor out lens focal length. In some cases you can but in other cases you can't. Interesting that you provided a link to a macro DOF calculator. In closeup and macro work it is possible to factor out the lens focal length so that DOF will = magnification + f/stop. But that won't necessarily work if you're shooting landscapes. Consider the example below using DOFMaster's calculator. You're going to have a tough time making the argument that 127 feet = 28 feet.

dof-lens-fl.jpg
 

unpopular

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This is incorrect. It's a common myth that you can factor out lens focal length. In some cases you can but in other cases you can't. Interesting that you provided a link to a macro DOF calculator. In closeup and macro work it is possible to factor out the lens focal length so that DOF will = magnification + f/stop. But that won't necessarily work if you're shooting landscapes. Consider the example below using DOFMaster's calculator. You're going to have a tough time making the argument that 127 feet = 28 feet.

View attachment 246114

This myth is one of the most baffling to me. Anyone who has used a a camera should have an intuitive understanding that FOV is not linear.


To illustrate this, I've plotted both DOF (red along y) at any given focal length (x) at a given working distance (d) at f/5.6 and a CoC limit of 0.05mm (both arbitrary).

I've also plotted the radius of FOV (black along y) at any given focal length (x) at a given working distance (d). So if you think of a subject as some percentage of this radius at any given focal length, one will find that to meet the same percentage at a different focal length the difference in working distance will increase significantly at short focal lengths than longer ones.

So putting this together, yes, it is true that at 1m with a 25mm lens you'll get the same DOF as a 50mm lens at 2m. However, your FOV radius will be 6.6m, where as your 50mm lens at 2m was at 2.1m. As a result, your subject will still be smaller at 25mm, even though you've cut your working distance in half.

If fact, to get the same radius your working distance would be at 32cm. However now your DOF is only at 91cm, whereas before with the 50mm lens and an equal radius of 2.1m was at 890cm - nearly ten times wider.

Naturally, this disparity is not nearly as severe with longer focal lengths, and doubling the working distance will approximately (but not exactly) double the fov when using a 100mm lens relative to a 50mm lens.

But one place where this has been commonly confused is with crop factor, and no, simply moving in closer to match the projection magnification of a full frame camera will not necessarily have the same result.
 

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