Wide aperture - Pictures out of focus

Started Aug 3, 2014 | Discussions thread
tedolf Forum Pro • Posts: 26,892

Truthiness wrote:

tedolf wrote:

Truthiness wrote:

tedolf wrote:

Christof21 wrote:

AnthonyL wrote:

Jizzy wrote:

tedolf wrote:

So, stop down to about f/8 and you will get a DOF of about 8-10 inches.

Now, you have to ask yourself why did you spend so much money for a f/1.8 lens when you really can't use it wide open for the types of photo's you want to shoot!


Yeah, thats what I am asking myself now

Yes - just get a P&S - no probs with DOF there!

Or stop down the lens, same results. This is not a "problem"

There are some situations where you can't stop down. Like where you need a faster shutter speed to avoid subject motion blur, e.g. father/daughter waltz at a wedding.

You can always stop the FF down 2 stops compared to your beloved m43.

Ok, now what just happened to your shutter speed?

I kept it the same? What's the problem?

Went from 1/125 to 1/30 sec., didn't it?

No. Why woud it? If I feel like it, I'll up the ISO,

caught you!

Now, what if you want the better dynamic range and lower noise of base ISO, or extended low ISO?

though I often shoot at ISO 100 (as I shoot raw and my camera is close to being ISOless).

So, you have a problem now don't you?

Maybe you don't understand that 1/125 on both cameras, the m43 needs two stops faster f-stop to allow the same amount of light to be used to draw the image on the image plane.

not for proper exposure.

Thus the image quality will be the same with these settings (1/125 with f/4 vs. f/2).

It wont be the same, if you changed you shutter speed (moving subject) or your ISO (dynamic range, noise).

What if 1/30 isn't fast enough?

What if you learned why I don't need to adjust the shutter speed.

The "problem" is that you are paying a lot of money for a fast aperture that is usable only in very rare circumstances.

Nonsense. I use sub-f/2 all the time. And I manual focus. And I get very good hitrate. I love to have that option.

Sigh, see above.

Sign, 1/125, f/4 on FF gives essentially IDENTICAL image to 1/125, f/2 on m43.

No it doesn't.  It is two stops darker unless you slow down your shutter speed two stops (possible subject motion blur, possible hand held camera shake blur) or you raise your ISO two stops (lower dynamic range, possible noise depending on what ISO you started at).

The FF lens at f/4 draws an identical (though scaled to be four times as large) image to m43 at f/2. Thus, the same amount of light is planted on the image plane. If the exposure lasts the same time, the image quality will be the same (disregarding sensor efficiency differences etc.)

None of that matters.  What matters is motion blur, dynamic range and noise, and those things are not the same with those settings.


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