Why does an increased aperture lead to blurry photos

topazsol · Jan 21, 2013

I was trying to take some photos of my cat in my bedroom tonight. She was asleep so she was perfectly still and I had more than enough light. I increased the aperture so I could get a blurry background and her face nice and clear. Every picture I took was blurry, the processing time was really long, like almost a minute.

How do people take photos with an increased aperture and have them turn out so clear? How can I decrease the processing time on my camera? Thanks for any suggestions.

Pallycow · Jan 21, 2013

without seeing it, I am guessing you were up close. When you increase the aperture you decrease your DOF (depth of field).

Basically the focal plane (area of your image in focus) is really really thin up close wide open.

Read up on DOF and you'll get a better understanding.

Pallycow · Jan 21, 2013

oh, and the second part of your question is pretty much impossible to answer as we have no idea about the camera, lens, settings, lighting, etc etc etc. all which have an impact on how the camera processes your image. So um....yeah. who knows?

Richichi · Jan 21, 2013

topazsol said:
I had more than enough light.

My thinking, based on no information supplied, was that there wasn't really enough light for the auto setting you were using. Therefore a slower shutter speed was selected and that you weren't able to hold steady, thus creating an improper focused image. To help you better moving forward when you post give us the camera data so that we could answer the question properly and helping you learn better.

Juga · Jan 21, 2013

Richichi said:
topazsol said:

I had more than enough light.

Click to expand...

My thinking, based on no information supplied, was that there wasn't really enough light for the auto setting you were using. Therefore a slower shutter speed was selected and that you weren't able to hold steady, thus creating an improper focused image. To help you better moving forward when you post give us the camera data so that we could answer the question properly and helping you learn better.

Ditto...

Scuba · Jan 21, 2013

I guess first what do you mean a larger aperture? Are you talking smaller or bigger number? Because the size is the opposite...the smaller the number the larger the aperture.

The second part is weird with the processing time. My bet is you have an inexpensive memory card and they are much slower to process.

SCraig · Jan 21, 2013

Scuba said:
I guess first what do you mean a larger aperture? Are you talking smaller or bigger number? Because the size is the opposite...the smaller the number the larger the aperture.

The second part is weird with the processing time. My bet is you have an inexpensive memory card and they are much slower to process.

Nope, not weird. My bet is that high ISO noise reduction is enabled. It works by taking the exact same exposure without opening the shutter to determine what is noise and what isn't. A 30-second exposure would then turn into a one minute exposure.

paigew · Jan 21, 2013

What were your settings? More specifically shutter speed?

enzodm · Jan 21, 2013

Scuba said:
I guess first what do you mean a larger aperture? Are you talking smaller or bigger number? Because the size is the opposite...the smaller the number the larger the aperture.

The second part is weird with the processing time. My bet is you have an inexpensive memory card and they are much slower to process.

I bet on f/22 -> "processing time" = shutter speed

cgipson1 · Jan 21, 2013

Post some images with the Exif data intact... we will be able to tell you exactly why!

TCampbell · Jan 21, 2013

cgipson1 said:
Post some images with the Exif data intact... we will be able to tell you exactly why!

^^^ This

Whenever you post a question about a problem you're having while taking a photo, you need to post the photo WITH all of the camera and exposure information (aka the "EXIF" data) intact. Note that some photo editors will strip out this data, but we need to see the camera, lens, and exposure info to be able to tell you what happened.

KmH · Jan 21, 2013

I would add that any lens has a minimum focus distance too.

Focus is not just about the lens aperture. How far from the camera the point of focus is, and the focal length of the lens, are also major factors.

All together it's known as depth-of-field - Understanding Depth of Field in Photography

Auto focus requires a minimum amount of light to work, but many cameras have an AF assist light the photographer can use in low light siturations.
Understanding Camera Autofocus

ManualMode · Jan 21, 2013

I'd be will to bet $100 that the OP went up to f22 to increase the Aperture, not realizing that in order to increase the Aperture, you need to decrease the f-stop.
Try again OP, go to the lowest number you've got and see what shutter speed you get then..

flow · Jan 21, 2013

How do you know you had more than enough light? What did your meter think?
Our eyes see much better in low light than the camera does, so it can be hard to accurately gauge just by looking.

vtf · Jan 21, 2013

Room light is by far not enough, use your flash to help with light. Don't get right up close and have your aperture around 4f. If on aperture priority the shutter will adjust and with flash the shutter should be fast enough.