Aperture on an APC camera
May 10, 2021 08:28:09 #
A smaller sensor is the same as cropping the image in post. No change in exposure.
May 10, 2021 08:35:00 #
CHG_CANON wrote:
This topic hasn't died down from 167 replies over 12 pages, and you're asking again?
https://www.uglyhedgehog.com/t-695357-1.html
If TN's technical expertise made him more than a self-proclaimed expert, why not ask him?
https://www.uglyhedgehog.com/t-695357-1.html
If TN's technical expertise made him more than a self-proclaimed expert, why not ask him?
But still many people are still confused with the crop factor. So regardless of how many replies or how many pages there are still people who can't understand the crop factor which is really not needed.
May 10, 2021 08:39:57 #
Ysarex wrote:
A lens set to f/2.8 is f/2.8 on all camera formats relative to exposure. The crop factor application to f/stop is to equalize DOF across the different formats. So if you want to take the same photo with both an APS format camera and a FF camera and have equivalent DOF between them then you use the crop factor on the f/stop. To get equal DOF the APS camera needs a wider aperture all else being equal.
You must also qualify by saying equivalent DOF for equal FOV ! - equal fields of view ! - no one ever mentions this - including Northrup ! - but it is CRUCIAL to understanding !
May 10, 2021 08:45:48 #
Miamark wrote:
I know that there has been some discussion about t... (show quote)
I think we just covered this nonsense a few days ago. Zzzzzzzzz
May 10, 2021 08:46:57 #
fetzler wrote:
Take CHG_Cannon's advice and do some reading. The focal length of you lens and its aperture are physical characteristics of your lens and have NOTHING to do with your camera's sensor size.
QED
If you don’t understand this statement I suggest you don’t pursue a career in science or engineering. Perhaps politics?
May 10, 2021 08:54:09 #
Longshadow wrote:
Worked for me....
I know, I know, it's much easier for people to keep asking the same question over and over,
and over instead of attempting to do any research.
I know, I know, it's much easier for people to keep asking the same question over and over,
and over instead of attempting to do any research.
Actually about the crop factor if you have to ask you wouldn't understand. It's a very simple concept and yet it get some people into serious confusion.
May 10, 2021 09:04:27 #
Ysarex wrote:
A lens set to f/2.8 is f/2.8 on all camera formats relative to exposure. The crop factor application to f/stop is to equalize DOF across the different formats. So if you want to take the same photo with both an APS format camera and a FF camera and have equivalent DOF between them then you use the crop factor on the f/stop. To get equal DOF the APS camera needs a wider aperture all else being equal.
The way I see it, the size of the aperture remains the same to get
a correct exposure whether the lens is used with a 35mm sensor or an APS-C camera.
Ysarex, the f number represents the ratio of aperture size to focal length.
For example f5 = an aperture 1/5 of the focal length; for a 50mm lens at f5 would mean
the the size of the aperture is 10mm.
Imho if you used the same lens with the same aperture on a
35mm sensor and then on an APS-C sensor the exposure of
the two images would be the same...
of course light and subject being equal.
May 10, 2021 09:10:13 #
If Tony Northrup, or his wife, told me what time it was, I'd pray I had an accurate watch to check for myself. Both of those characters are out in left field, perhaps not even in the ball park.
--Bob
--Bob
IDguy wrote:
Check out Tony Northrup’s youtube on this. He convinced me.
There is no impact on exposure.
It does affect depth of field.
Just something to consider when buying lenses and choosing settings.
There is no impact on exposure.
It does affect depth of field.
Just something to consider when buying lenses and choosing settings.
May 10, 2021 09:13:50 #
Canon Guy, good response. I read this column almost every day but some of the questions are beyond basic. And lots of "expert" responses. But you are always the voice of wisdom and reason.
May 10, 2021 09:18:28 #
May 10, 2021 09:38:39 #
zug55
Loc: Naivasha, Kenya, and Austin, Texas
Miamark wrote:
Could someone explain this to me why, as Tony Northrop (a respected source) and suggests, that you have to multiply the aperture by the crop factor as well.and end my confusion.
I think that you have pretty good understanding how this works. I think that the issue is that Tony Northrop created some confusion with his misleading statement.
For example, full-frame and APS-C 50mm lenses let through the same amount of light at the identical aperture. What changes is the field of view.
If you shoot the same scene, once with an APS-C at 50mm and once with a full-frame camera at 75mm, with otherwise identical settings, you get approximately the same image with the identical field of view. The difference is that if you shoot this scene full-frame at 75mm you get a shallower depth of field and better compression, and the background of the image as a result is blurrier and you get a better bokeh. If you want to get a comparable compression and bokeh in your APS-C image, you will have to open up your lens by the same crop factor.
May 10, 2021 09:57:27 #
Miamark wrote:
I know that there has been some discussion about t... (show quote)
EXPOSURE does not change
DEPTH OF FIELD becomes approximately the same as a full frame lens with the same FIELD OF VIEW from THE SAME DISTANCE, *AS IF* the aperture were one stop smaller.
Full Frame 50mm lens set to f/2.8
APS-C 35mm lens set to f/2.8, EFFECTIVE DEPTH OF FIELD is equivalent to full frame 50mm used at f/4
Micro 4/3 25mm lens set to f/2.8, EFFECTIVE DEPTH OF FIELD is equivalent to full frame 50mm used at f/5.6
From the same distance, these three combinations will have almost identical composition/field of view. But the exposure is set at f/2.8 on all of them! But the smaller sensors used with shorter lenses yield more depth of field.
If you have a smartphone, download a depth of field calculator, plug in all the variables, and prove it to yourself.
May 10, 2021 09:59:36 #
imagemeister wrote:
You must also qualify by saying equivalent DOF for equal FOV ! - equal fields of view ! - no one ever mentions this - including Northrup ! - but it is CRUCIAL to understanding !
DoF is also based on an equally simple geometric argument. Understanding is bit tricker because is also depends on a circle of confusion which is a subjective judgement of “acceptable” focus a viewed from the image (film or sensor) plane. Technically, the subject is in perfect focus at exactly one distance which is zero DoF. Not a useful concept. Think of DoF as a rule of thumb since it depends on how you view the resulting print which depends on the magnification and viewing distance.
Again the lens doesn’t change when you mount it on a different camera.
May 10, 2021 10:17:40 #
StanMac
Loc: Tennessee
imagemeister wrote:
You must also qualify by saying equivalent DOF for equal FOV ! - equal fields of view ! - no one ever mentions this - including Northrup ! - but it is CRUCIAL to understanding !
Now THAT clarifies the DOF difference question precisely! Thanks Larry!
It made no sense to me that for a subject at the same distance from the imaging medium (film or sensor) the DOF would vary at the same aperture setting depending on the size of that imaging medium.
Stan
May 10, 2021 10:43:58 #
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