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Landscape focal point

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Blueiris07
45 posts
Message posted at 02/22/2013, 10:52:53 AM by Blueiris07
This probably has been discussed somewhere on this forum but I could not find the reference. I have submitted a number of landscape images that have been rejected for "focus not where we think it should be". I have tried focusing my shots everywhere on the canvas so to speak. Where might I focus to have the best 'shot' of exceptance if everything else is right? An obvious focal point is not my problem. I generally focus a third way(??) up into the image.
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Nospmisk
364 posts
61
Message posted at 02/22/2013, 10:58:30 AM by Nospmisk
Read This
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Blueiris07
45 posts
Message posted at 02/22/2013, 11:47:01 AM by Blueiris07
Thank you!
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68
Message posted at 02/22/2013, 14:55:07 PM by Robinstockphotos
The article is the theory part, and for practice I know the best thing.
If you have an iPhone or Android phone, go to the market and search for depth of field (DoF) calculator applications. They ask for sensor size and other stuff. Try various combinations and see how it works.
For example, focusing a 55mm lens at 80m might give you maximum DoF at that aperture while 100mm lens would give maximum DoF at 200m focus point distance for that aperture.
Use the app, I learnt this stuff in 15 minutes! :)
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Blueiris07
45 posts
Message posted at 02/22/2013, 15:08:46 PM by Blueiris07
I don't have an iphone or Android. This is all goobledegook to me. I have to read it all. Can I get this application elsewhere?
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Afagundes
3244 posts
<10
Message posted at 02/22/2013, 16:59:35 PM by Afagundes
Blueiris07, one rule of thumb is to focus at one third of the distance, so you focus on the more distant thing you want on your image, than on the closer one and change the focus to one third of it,

Say, 65 meters is the further, 5 meters is the closest, than you would focus in 25 meters,

You don´t really need to be that precise, just focus at where you think is one third, you wont get too wrong.

If you want a lot of it to be in focus you need to stop down the lenses a bit, on your camera around f11, dont close it more than that because other effect called diffraction will start to appear, ok, maybe f13,..., I encourage you to do some experiments to see how does it work.

Cheers!
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68
Message posted at 02/23/2013, 02:35:09 AM by Robinstockphotos
Do some searches on Google and find out. You might get a PC version of something. Or some website.
Afagundes is right, experiment and experiment. Theory almost always fails in unusual situations and unfortunately the unusual situations are almost always the bestsellers. haha!

If you feel doubtful about the focus thing, you can use focus bracketing feature.
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Blueiris07
45 posts
Message posted at 02/23/2013, 07:41:03 AM by Blueiris07
Thank you again. I guess much of my frustration is not knowing where ******** wants an individual image to be focused. It seems they all differ. I have tried to focus in the same area with the same camera settings and some are accepted and some are refused for that reason. I would love to be told just where they want the focus in the image they are refusing. That would help me understand.
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Miraclemoments
1197 posts
72
Message posted at 02/23/2013, 14:02:52 PM by Miraclemoments
If you are doing landscapes you need to stop down to at least f9 and like afagundes said...focus at around the 3rd part of the image. You can even use your focus points to select a fixed focusing point. If you have live view on your camera use that to select your area of focus.

Find the best aperture for your lens...some lenses cause diffraction if you stop down to much. Comes down to experimenting again as mentioned.

The main thing with landscapes is focus/sharpness right through the image. Front to back. Check the settings you used on the rejected images and try and determine what went wrong.

good luck!!
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68
Message posted at 02/23/2013, 14:42:07 PM by Robinstockphotos
From basic optics, you'd get troublesome diffraction after f/8.0 if you're using very cheap lens. Otherwise let f/11.0 be the usual one. It is pretty good.
You can even use f/1.8 in a landscape shot if you want to focus on some subject, for example, a horse.
If you have a horse there and you are using f/11, you should focus on the horse rather than 1/3rd distance. A blurred horse in a perfect landscape is a rejection. First priority is to keep the subject focused, second...get it all focused with 50mm or something, f/8 to f/11.

A tale of my foolishness:
I used f/32 at 18mm to photograph a waterfall at 2s shutter speed. The lens wasn't good enough and I got seriously bad diffraction problems around little leaves and grass. It is totally unusable even though I resized it to 3MP...the leaf outlines still feel abnormal. So if you want a slow shutter speed and sunlight together, use special filters...don't use f/32 like me.
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Lehmanphotos
139 posts
<10
Message posted at 02/26/2013, 16:53:34 PM by Lehmanphotos
Thanks for the link, Nospmisk.
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Afagundes
3244 posts
<10
Message posted at 02/26/2013, 20:39:14 PM by Afagundes
I am listening to people saying difraction due to bad lenses.
Maybe I am wrong, but I think difraction is an optical effect that will happen in any lens, there is no way to get rid of it, bad or good lens of you close down too much difraction will show up.
Other types of distortion might come from a bad lens, but difraction I though was entirely due to an optical effect.
But, as I said, I am not an expert so I am launching the question maybe for someone to tell me that I am wrong, lets see what you guys have to share here with me.

Robinstockphotos I did something like this, took a lot of images stopping down to f22 thinking I was getting everything in focus, difraction ruined a lot of my images, tough way to learn.
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Danielc1998
139 posts
68
Message edited at 02/27/2013, 04:20:27 AM by Danielc1998
I am not an expert either, but as far as I have read and learnt, diffraction happens each time the light passes through a tiny hole.

It have nothing to do with the glass of the lenses, but with the aperture you use. The smaller the aperture the larger the effect due to the wave nature of the light.

The pattern of diffraction creates a series of rings called airy disk.

What cause a lost of sharpness in the images is the combination of the size of the airy disk and the size of the pixel in the camera sensor. If the diameter of the airy disk is larger than the size of the pixel sensor of the camera, you will see a loss of sharpness.

Also if the airy disk of two different points reaching the sensor are overlapping each other, at one point they will look like only one point (if the disks are too big) and loss resolution, and sharpness.

Two different cameras with sensors of the same size (say full frame), one with 8 MP and the other with 32 MP, the 8 MP will allows you to stop down much more than the 32 MP before diffraction became a problem, because the pixels are larger (assuming they cover the whole surface of the sensor).

With my canon 550d i never use an f stop larger than f/16 despite the camera allows me to go up to f/36. ...Actually it is the lens that allows me to go that far, as the mechanism is in the lens. Using the same lens with another camera the max f stop that will cause loss of sharpness due to diffraction will be different.



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Parkinsonsniper
1091 posts
72
Message edited at 02/27/2013, 08:25:32 AM by Parkinsonsniper

Originally posted by Afagundes:
Quoted Message: Blueiris07, one rule of thumb is to focus at one third of the distance, so you focus on the more distant thing you want on your image, than on the closer one and change the focus to one third of it, Say, 65 meters is the further, 5 meters is the closest, than you would focus in 25 meters, You don´t really need to be that precise, just focus at where you think is one third, you wont get too wrong.If you want a lot of it to be in focus you need to stop down the lenses a bit, on your camera around f11, dont close it more than that because other effect called diffraction will start to appear, ok, maybe f13,..., I encourage you to do some experiments to see how does it work. Cheers!


This is right...you can safely follow this explanation :)

As Afagundes mentioned politely and DanielC mentioned techniquely; diffraction is a natural happening and we can't get rid of it buying expensive and high quality lenses. Every optic suffers from diffraction.

My personal addition is;

When you take a landscape shot using a wide angle lens, it's very hard to miss the focus. Your problem made me think that your lens might have a problem in "focussing to infinity". I remember...my old Nikkor 105mm was not able to focus to infinity. Maybe yours have the same problem. Just an alternative opinion...
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Blueiris07
45 posts
Message posted at 02/27/2013, 09:16:07 AM by Blueiris07
You may be right there. I use an 18-70 Nikon zoom lens and and a 70-300 lens. I have tried aperture priority at 11 and 13 and don't get the sharpness that I thought I would get. I try mainly to focus 1/3 into the frame unless there is a specific main subject. I do not always use a tripod though. This is all secondary to my original post although I have benefited from the answering posts emensely.

Even when the subject is dead on sharp I sometimes get rejected for this reason. That is why I originally posted. I don't know what the site is looking for. I get lucky enough I guess.
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Parkinsonsniper
1091 posts
72
Message posted at 02/27/2013, 09:23:02 AM by Parkinsonsniper
Then the best thing to do is to ask admins, about the cause of rejection. They are extremely helpful in such situations. I remember an admin sending me a picture of mine, a dust with red circle around it for me to see LOL
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Danielc1998
139 posts
68
Message edited at 02/27/2013, 10:35:28 AM by Danielc1998
When shooting without a tripod a good rule, to avoid blurred shaken images is to use a minimum shutter speed inversely proportional to the focal length you use.

That is, if use are using a focal length of 300 , then the shutter speed should be not slower than 1/300 (for full frame sensors), the IS could give 1 or 2 stops margin, so 1/150 or 1/75 could be used. For cropped sensors you have to multiply it by 1.5 o 1.6, so 1/300 became 1/450 for a crop factor of 1.5.

Also, I got good results focusing to infinity (much easier to select) rather than the hyperfocal distance when I want everything in focus.
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Blueiris07
45 posts
Message posted at 02/27/2013, 10:24:03 AM by Blueiris07
Thanks and thanks! I think that I will work on the technical adjustments to my work before I get to nagging admin. too much. I gotta dig out the tripod-----
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