Why difference in focus

[Tatiana_]

Image 1 is F 4.0, ISO 80, 1/640
Image 2 is F 4.0, ISO 100, 1/60
They are taken with 2 different cameras. One is in focus, one is now with the same F stop. Why? What could have been different in image 2?

Thank you

 

[Tatiana_]

Pictures are attached

 

[Derrel]

Well, the first shot was made with a Canon PowerShot camera, with a very small sensor and a 6 millimeter lens focal length, and it shows a wide-angle, low-magnbification image. Due to the small sensor, short lens, and wide-angle, low-magification image, there is adequate depth of field, and most things look "acceptably sharp", which is a criterion of depth of field--that things look "adequately sharp" in an image, seen at a particular size, from a range of so-called appropriate viewing distances.

The second photo was made with a Canon Rebel T4i digital SLR and 28mm lens, using a MUCH BIGGER sensor, and a lens that is over 4x longer, and is NOT a wide-angle segment of the scene. The larger sensor, longer lens, and relatively magnified view all combine to give significantly LESS of the scene that is rendered "acceptably sharp". As you look at the building fronts, you can see that the acceptably sharp areas "drop off" to blurriness around 100 feet behind the man.

The angle of view is different; the camera sensor size is different; the picture angles are different; the first shot is VERY TYPICAL of the results that one gets with a small-sensor compact digital camera with its very short focal length lenses; the second frame is pretty typical of how a 28mm lens on a larger-sensor APS-C d-slr behaves.

 

[Tatiana_]

Another sample in the similar situation. Both are F4.
Image 3 is ISO 160, 1/100,
Image 4 ISO 80, 1/125

Even Image 5 with only 3.5 F stop is in focus, ISO 200, 1/160.

When I try hard with the "not focusing camera", it works fine. But on the go, in Auto mode nothing works!
Please help. Trying to understand what I'm doing wrong.

 

[Tatiana_]

Derrel,
Ok, how do I correct that with T4i. What would you recommend?

 

[Tatiana_]

I have couple hundred pictures from both cameras. T4i - almost all are trash! Nothing is in focus. Powershot worked ok in a variety situations.
So what do I need different with T4i in the future?

 

[bratkinson]

To me, the 'nothing in focus' from your T4i suggests any or combination of 4 possibilities:
1. Too slow shutter speed - 1/60th is too slow to reliably 'freeze' people
2. Are we looking at the full image? Or are these pictures heavily cropped and what actually is in focus has been cropped out?
3. There may be a problem with your equipment settings:
a) Is the lens is set to AF?
b) Are the internal settings of the camera the 'factory settings'? Choosing incorrect modes can cause problems
4. The camera and/or lens is defective. To test, go to the menu and select 'restore factory settings', put lens on AF and take some pictures in reasonably bright light.

 

[greybeard]

My answer: (f) numbers (factor) are relative and not fixed like shutter speed. An f/4 on a lens designed for a POINT AND SHOOT that has a "normal" angle of acceptance will have a much deeper depth of focus than a shot taken with a FULL FRAME camera with a 50mm lens set to f/4. DoF and how it relates to f/stops is relative to the size of the sensor (format).

Perceived DoF is also relative to the angle of acceptance a lens creates with a given sensor size (format). The wider the angle, the deeper the perceived DoF. In your pictures, as Derrel pointed out, you not only have cameras with different formats (sensor sizes) but the lenses do not have the same angle of acceptance. Apples and Oranges.

 

[Braineack]

What could have been different in image 2?

Thank you

almost everything from that of image one, except f/4.

 

[photoguy1510]

May I suggest you do a free photography cource, simply to understand how the image is recorded. This should explain why your seeing the differance.

Alternative to the course is get scott kelbys book " the digital photography book" the first book will answer in detail this question and the next 10 that will follow book 2-5 is more examples of how to take photos and use flashes ..... But book one i think is a must read for any first time slr user. Easy light reading with a joke or two to keep you interested.

The biggest advantage of your slr is arguably to capture less detail if you want your settings are for less detail.

Get away from auto mode set camera to ISO400 + and F8 and try again you should see an improvment.

There is a lot that affects the result
Camera ( little)
Lens (a bit more)
Depth of field (a lot)
Hyper Focal distance ( fair bit)
....


Sent from my iPad using Tapatalk

 

[qleak]

There are phone apps for determining the apparent depth of field:
I use this one:

HyperFocal Pro - Android Apps on Google Play

As Derrel explained, the format of the sensor (or film) is quite significant for the depth of field.

It looks like you may be interested in hitting the hyperfocal distance:
Hyperfocal distance - Wikipedia, the free encyclopedia

 

[vintagesnaps]

I agree with bratkinson, I'd try resetting to factory settings. It seems like something's wrong if you're getting a lot of pictures like #3 when you've got it set to auto.

You said when you try hard with your nonfocusing camera, do you mean that if you adjust settings yourself that the pictures are in focus? But when you're on the go in auto they're blurry?

If so, I'd keep trying to use manual settings and learn how to read the meter to figure out how to adjust the aperture and shutter speed and ISO. I usually don't set a camera slower than 1/125 unless I'm in low light and then I get balanced to support the camera well. It depends on how good you are at hand holding a camera. My starting point is usually f8 so I'm at a midrange setting, then I can open the lens a stop or two more or go to a smaller aperture, fairly efficiently. I usually use 100 or 200 ISO outdoors on a sunny day and 400 in lower light to start with, and then adjust from there.

If you can get good photos with the camera when you're not in auto, then maybe take along a little notebook and write down what you did when you set the camera yourself so later when you go thru your pictures you might figure out what worked and what didn't.

 

[Tatiana_]

I appreciate everyone's input.

 

[Tatiana_]

May I suggest you do a free photography cource, simply to understand how the image is recorded. This should explain why your seeing the differance.

Alternative to the course is get scott kelbys book " the digital photography book" the first book will answer in detail this question and the next 10 that will follow book 2-5 is more examples of how to take photos and use flashes ..... But book one i think is a must read for any first time slr user. Easy light reading with a joke or two to keep you interested.

The biggest advantage of your slr is arguably to capture less detail if you want your settings are for less detail.

Get away from auto mode set camera to ISO400 + and F8 and try again you should see an improvment.

There is a lot that affects the result
Camera ( little)
Lens (a bit more)
Depth of field (a lot)
Hyper Focal distance ( fair bit)
....


Sent from my iPad using Tapatalk

I will get the book. Thank you

 

[Tatiana_]

May I suggest you do a free photography cource, simply to understand how the image is recorded. This should explain why your seeing the differance.

Alternative to the course is get scott kelbys book " the digital photography book" the first book will answer in detail this question and the next 10 that will follow book 2-5 is more examples of how to take photos and use flashes ..... But book one i think is a must read for any first time slr user. Easy light reading with a joke or two to keep you interested.

The biggest advantage of your slr is arguably to capture less detail if you want your settings are for less detail.

Get away from auto mode set camera to ISO400 + and F8 and try again you should see an improvment.

There is a lot that affects the result
Camera ( little)
Lens (a bit more)
Depth of field (a lot)
Hyper Focal distance ( fair bit)
....


Sent from my iPad using Tapatalk

Are there any particular courses you'd recommend?