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01-03-2011, 06:15 PM   #1
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how much can you zoom in?

I am trying to work out whether I constantly have out of focus images or if I expect to much. I am trying to understand if you zoom in on a image or crop a section out which then zoom in at what point should what appeared to be in focus become distorted if that makes sense?
in the attached image the third tree on the left should be in focus. taken on a tripod , little green hand on, timer used ect to stop shake.
the third tree on the left looks ok but as you zoom in it gets to look very out of focus , is it or is it me, am I trying to zoom in to much?
I can post other examples if required.
Alistair


Last edited by adwb; 03-31-2012 at 07:01 AM.
01-03-2011, 07:15 PM   #2
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QuoteOriginally posted by adwb Quote
little green hand on, timer used ect to stop shake.
Little green hand is Shake reduction? If so... You're on tripod and using timer... Turn Shake reduction off... Its seeking shake and effectivly creating its own...

I can't see your exif data but guessing fairly open aperture f3.5 maybe... Also guessing f8 or smaller would look much sharper...
01-03-2011, 07:22 PM   #3
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What point are you focusing center or 11 points? Also what you have is deep of field will lower apperture.
Time to get a good book on understanding this
01-03-2011, 07:41 PM   #4
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What I see is that you've got a misunderstanding of depth of field.

That's the portion of the image you wish to be in focus, while other portions are out of focus.
You might not have run into that before if you had a point-and-shoot camera, because they don't have that capacity.

Sure, it might immediately sound awesome to have everything in focus, but the idea is to get what you wish to have in focus, while the rest might be out of focus. What the effect does is POP the portion that's important to you almost like a 3D effect.

That's why people use DSLRs.

Here's a link that explains it:
Understanding Depth of Field in Photography

If you look at the center of your image, it's sharp and in focus. The bottom and top are out of focus. If you'd be taking a portrait, it would be a pleasant effect, and draw the eye to your subject.

You'll even find discussions about lenses that have a better looking out-of-focus effect than others (they call it bokeh).

That said, you can have your complete image in focus if you wish, or only some portions of it. That's why DSLR photography is complicated but rewarding, and why you have all these settings...So you can make the picture how you want it, whether it be how the light shines, the colors, how movement is either frozen or blurry, and even what's in focus and what's not.

Have a good time learning. I still am, and will be learning for however long I take pictures.

01-03-2011, 09:54 PM   #5
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I don't think adwb is complaining about DOF or lack thereof as he clearly states that it looks OK till he zooms in.

I think you're trying to zoom in too much. A 100% crop of the tree area will help to judge it.
01-03-2011, 10:35 PM   #6
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QuoteOriginally posted by sterretje Quote
I don't think adwb is complaining about DOF or lack thereof as he clearly states that it looks OK till he zooms in.

I think you're trying to zoom in too much. A 100% crop of the tree area will help to judge it.
it's DOF, lol, when you're zoom in (aka longer FL the DOF becomes very thin when you have the same aperture).

for example my 70-210 f/4. if i sit at 70 f/4 my DOF is thicker than 210 @ f/4...

Now I'm pretty sure I might be wrong, but I remember someone said that an 100mm f/4 will have the same DOF as a 50 f/2... I'm thinking that's not right since my head isn't good these days but you get the idea.

so like people have been saying, raise your aperture number up to like 8-11 and it should all be in focus.
01-03-2011, 11:10 PM   #7
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See opening post:
- zoom in on an image
- crop a section

I read that as there is an existing photo. Let's see what OP says.
01-04-2011, 01:11 AM   #8
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When you zoom in by cropping the photo, the individual pixels get larger. When they get larger than the dots on your computer screen the image gets fuzzy.

There are about 1000 dots in the width of the photo on your computer and about 3000 dots across the camera's image (for a 6meg sensor), so a 3x enlargement is about the maximum enlargement theoretically possible. We can't actually enlarge that much usually, because our camera's lenses aren't good enough to fit a spot of light on an single sensor pixel.

Think of a scene's depth as a fraction of its width; a consequence of the above logic is the fractional depth remains constant as you zoom in on the scene. In the photo you posted, the in-focus depth is about 1/5 of the scene's width. If you enlarge a bit, the same depth fraction of the enlargement stays in focus, so enlargement gains little or no depth.


Last edited by newarts; 01-04-2011 at 01:17 AM.
01-04-2011, 01:52 AM   #9
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QuoteOriginally posted by newarts Quote
When you zoom in by cropping the photo, the individual pixels get larger. When they get larger than the dots on your computer screen the image gets fuzzy.

There are about 1000 dots in the width of the photo on your computer and about 3000 dots across the camera's image (for a 6meg sensor), so a 3x enlargement is about the maximum enlargement theoretically possible. We can't actually enlarge that much usually, because our camera's lenses aren't good enough to fit a spot of light on an single sensor pixel.

Think of a scene's depth as a fraction of its width; a consequence of the above logic is the fractional depth remains constant as you zoom in on the scene. In the photo you posted, the in-focus depth is about 1/5 of the scene's width. If you enlarge a bit, the same depth fraction of the enlargement stays in focus, so enlargement gains little or no depth.

lol, his question didn't really make sense before i read your answer.

to OP
1) you don't need to zoom in, you can already tell where the camera was focusing from the original picture.
2) you want everything to be sharp evenly, dial up the aperture number and it'll keep almost everything in focus (f8 to 11).

try it.
01-04-2011, 02:51 AM   #10
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QuoteOriginally posted by sterretje Quote
I don't think adwb is complaining about DOF or lack thereof as he clearly states that it looks OK till he zooms in.

I think you're trying to zoom in too much. A 100% crop of the tree area will help to judge it.
Yes you are correct, I am well aware what d.o.f. is and how to achieve the results taking into account the aperture used. I thought the exif data was available to be seen in the photo but here it is 1/200 at f14 iso 1000
Perhaps I worded my OP. badly it was very late at night. so let me try again.
I often have images which when viewd as taken on a 24"" screen and in print even up to A3 size the point of focus looks sharp as in the attached example 2nd tree on the left.

However at 100% or when enlarged by cropping the "in focus " part rapidly starts to look out of focus . What is a reasonable amount of zoom that you should be able to apply before distortion [or pixalation if you like] becomes apparent?

In LR when the tool selected is the magnifing glass if I zoom in to 33% in LR on ANY image then the ruler size on screen matches a ruler held up to it.
Is this then actually viewing print size rather than the larger size shown by using the print size option button?

Using the 1:1 option which I assume = 100% then any image is distorted but 1:1 surely is a total over magnification is it not?
attached original and 100% crop and thin one which is enlarged to 33% then cropped.

Last edited by adwb; 03-31-2012 at 07:01 AM.
01-04-2011, 03:02 AM   #11
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OP

couple of questions Mate

are you shooting Raw of Jpeg ?...if Jpeg...stop and starting shooting raw...much more information for the computer to work with...better image Res and all that

if you are shooting raw..what lens are you shooting with to get the above results ?... remember the sharper the lens. the more you can crop in and still retain the detail, if the lens is not so sharp...100% crops do look ordinary and blurred
01-04-2011, 03:07 AM   #12
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raw demo images converted in LR for this post.
lens is a 55-300 da
01-04-2011, 03:30 AM   #13
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no worries mate..heres a test I did for you using my super sharp and super new sigma 17-50..and my not so sharp and not so new sigma 70-200

both were at 2.8..the 17-50 at 50mm and the 70-200 at 118mm to keep the filed of view the same ....the 100% crops are from each image respectively ....

As you can see at normal view both look sharp enough...but when 100% zoomed in. the poorer of the two looks blurred. or when talking Lens sharpness...most round here would say SOFT...

hope this helps mate

Image 1


Image 2



Image 1 crop @ 100%



image 2 crop @ 100%


01-04-2011, 03:44 AM   #14
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I have the 55-300mm DA lens as well, and I am afraid this is what you get at 300mm. It does tend to be soft at the long end. I have a Sigma 70-300mm, and if it's any comfort, that one is even softer!

At least your photo corresponds well to my own experiences with this lens at 300mm. It's still better than NO 300mm - but isn't prime quality for sure. I just purchased a used prime 300mm f/4, and I look forward to doing some comparisons of the two.
01-04-2011, 03:53 AM   #15
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just had a look at the specs of that lens and the EXIF of your image...you are at 300mm, that's right up the weak end of the 555-300 as as far as MTF resolution tests are concerned..at the borders {where you tree is} the lens drops off quite a lot in resolution ..this would add to your blurred out crop a lot IMHO

after all said and done..the "as" captured image looks good.....if you wanna crop in and have decent res at that FL..your gonna need a 60-250 DA*
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