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Old Mar 18, 2007, 10:55 PM   #1
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I recently picked up the Canon 50mm 1.4, and was doing some DOF shots. One thing that I noticed, and think it is also true with my other lenses, is that what I see TTL is not the image that I get on the card.

Example, If my subject is 3 ft away, and the wall being 10 ft away has a wallpaper pattern on it. Shooting 1.4 would give me a blurred background obviously, and would be the intended shot. Yet, when looking through the viewfinder, I see more detail and not as much blur as when the shot is complete on the card.

Would anyone know why this is the case? Cause it is kinda bugging me a little.
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Old Mar 19, 2007, 5:07 AM   #2
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You are enlarging less when looking through the viewfinder.
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Old Mar 20, 2007, 3:56 AM   #3
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That would be because the aperture hasn't changed to suit the desired aperture you have dialled in.

You should have a DOF Preview button, which once pressed, will change the aperture accordingly. To be honest I haven't tried it myself to any great extent to know how effective it is.


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Old Mar 20, 2007, 9:10 AM   #4
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peripatetic wrote:
Quote:
You are enlarging less when looking through the viewfinder.
Let me put some meat on the bones.

chonkerwrote:
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That would be because the aperture hasn't changed to suit the desired aperture you have dialled in.

You should have a DOF Preview button, which once pressed, will change the aperture accordingly. To be honest I haven't tried it myself to any great extent to know how effective it is.
Sorry to say this is not the reason, as Buhammot stated the camera is setto f1.4 which is the brightest/widest it can be and when framing etc the camera always uses the widest aperture possible to allow as much light in so that AF works and you can see clearly to frame. As the aperture is as wide as it can go then the dof would be reduced as far as is possible.

Here is an example of what is happening and for this I will use a hockey shot recently taken.

When looking through the view finder then you have only a limited view of the shot and might look something like this.



(OK so not a great shot as I missed the ball but never mind)

You will notice that the umpire islooks prettyclear.

When going to a 100% crop you then you get the following:



Only now can you see how blurred the background is so there you have it.

Hope that helps.
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Old Mar 24, 2007, 10:43 PM   #5
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Close mark, but still not quite. Even when looking at the image taken vs through the lens, its like it is about 30% of the DOF vs looking through the lens alone.

BTW, the DOF Preview only works when stopping down the aperature. As mark has stated, when the lens is wide open, it just goes click, (meaning providing no assistance, as none can be provided).
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Old Mar 25, 2007, 7:32 AM   #6
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Even when looking at the image taken vs through the lens, its like it is about 30% of the DOF vs looking through the lens alone.
I don't understand that sentence I'm afraid.


I don't think you understood what Mark & I have been trying to say.

If you take the same image and print it to two different sizes the smaller picture will seem to be more in focus. The bigger picture will seem to be more out of focus - i.e. have a smaller DOF.

The reason things look in-focus in the viewfinder is because they are very small compared to prints or on-screen.


http://en.wikipedia.org/wiki/Circle_of_confusion

http://en.wikipedia.org/wiki/Depth_of_field
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Old Mar 25, 2007, 9:20 AM   #7
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I understand what you guys are saying, but this is still not the case. For example, I was just double checking some things, taking some sample pictures of some simple wallpaper, very repetitive in design. When I was viewing the photos, some taken 1.4, some 2.8, i could see a pretty big difference in them, considering. But when I went and did use the DOF preview, Av setting at 2.8, I saw much less difference than the images were shown, and this is with the view finder.

Lines that were out of focus obviously are a large blur near the edge of the frame, but still distinguishable since they are also in focus in the center of the frame. When wide open, and TTL, they are less blurred or more in focus than what the image would show. I understand about the whole magnification thing, just that there is more detail there.

Another example when I was at a local climbing gym. Some of the ropes were hanging up, and I was testing my lens in low light, so f/1.4. I took a few shots of the ropes about 2 ft in distance, and TTL, i could see that there was a banner and the top corner of the building, blurred, but distinguishable. distance from ropes to corner of building, prolly close to 75 ft. When viewing the image, i was only able to see a blurred background only showing colors for the banner and the brick wall, and I couldnt identify the corner.

Like I said, I understand what your saying about the size and magnification of the viewfinder, but the images show a larger difference in aperature sizes than what i actually see when set to for example, f2.8, then pressing the DOF preview button.

Edit:

So I just did some simple tests once again for more accutare information. When viewing through the viewfinder, what I see is best represented by an image taken at f/4. Keep in mind that this is WITHOUT pressing the DOF preview, meaning the lens is wide open at f/1.4.
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Old Mar 25, 2007, 10:54 AM   #8
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Quote:
I understand what you guys are saying, but this is still not the case.
No you don't. Read it again.

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When viewing through the viewfinder, what I see is best represented by an image taken at f/4. Keep in mind that this is WITHOUT pressing the DOF preview, meaning the lens is wide open at f/1.4.
That is exactly what we are saying you should see. More DOF through the viewfinder than is apparent when looking at the shot in a print or on screen. [But it all depends on how big the enlargement is on screen or in print.]

The links I posted tell you why this is the case. Of course you don't actually need to understand why, just remember that what you see in the viewfinder is not exactly what you will get in the image.
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Old Mar 25, 2007, 7:45 PM   #9
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I understand the whole idea of the magnification thing, which is obvious; that when something is smaller it is harder to see more detail, so it would appear to be more in focus or more DOF in this case.

Basically, in a nutshell, what yall are saying, is that what you see is NOT what you get when dealing with larger aperatures. I am just saying what I am experiencing here nothing more. Regardless of viewing size, less DOF is present on the image that what is seen, which can be a good thing at times.
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