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04-17-2010, 04:52 PM   #1
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I've been learning a lot about ISO, Aperture and Exposure :)

Well I have had my camera for 3 days now. I did not shoot any yesterday but did a lot on the first day and learned a ton!

Here is a link to my 1st day's pics.
https://www.pentaxforums.com/forums/pentax-beginners-corner-q/97770-new-dslr-...-critique.html

In a nut shell I have really been reading about ISO, Aperture and exposure and how they all work together.

Here is a pic from today I took
I learned that (for this pic) low ISO high aperture and long exposure make for a much better pic.

I took the shot first in full auto and it tried to take the pic at F8 and 1/10 ISO 800

I too it at ISO 200/F32 with a full 3 second exposure.
Focal length 300mm

Of course with a tripod and 2 second timer.
Manual focus.

For reference the entire flower is about the size of a kernel of corn.
It's a house plant from the living room.



For re

04-17-2010, 05:07 PM   #2
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Looks good, but you're probably not going to get that good of results (even with the Shake Reduction on) at ISO 100 and 1/10 second. Don't be afraid to try and use other ISO settings until you get a good photo, but remember that after ISO 1600 things start to go downhill.

Otherwise your photo looks very good, but you need to keep experimenting with your settings until you find one that makes practical sense, I wouldn't do a photo like this with Shake Reduction on under 1/60th second, just to be sure there's no motion blur anywhere in it.
04-17-2010, 05:16 PM   #3
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This is not a bad shot at all, especially since you are relatively new to the DSLR world, but there are a few things that need to be cleared up. First, let me congratulate you for actually reading and researching the topic and how to take proper photos. All too often we get people asking questions that they could have easily have found in the manual, but just decided not to look. This shows that you are passionate about photography and I look forward in seeing some more of your photos in the future.

Now on to your photo; I am guessing that you read that the smaller the aperture the sharper the photo will be. While that is a correct statement, if you go close the aperture to the smallest position (f/32) you will end up with a problem called diffraction. As you stop down the aperture on a lens the light passing through tends to diffract, reducing sharpness, though DOF is increased. The reason for this is that the edges of the diaphragm blades in the lens tend to disperse the light. At larger apertures this diffracted light is only a small percentage of the total amount of light hitting the sensor or film, but as the aperture is stopped down the amount of diffracted light becomes a larger percentage of the total amount of light being recorded.

So I hope this helps you understand what is happening when you stop down the lens that far. However, it seems you have a good understanding of shutter speed and ISO so I won’t talk about that now. You also seem to know that the use of a tripod is very important and you even used you mirror lock up feature to take the above photo so that is very good as well. Anyway, I wish you luck with your new camera and as I said before I look forward in seeing some more photos from you in the future.

Cory
04-17-2010, 06:32 PM   #4
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Thank you!
The only reason I used such a high aperture was because I was having trounle getting all the petals of all three flowers in focus.

It's only about 3/8" depth between the three.
This seems to be the hardest part for me to understand.

Is there any reading that would explain the relationship between DOF/Aperture/and Focal Length?

04-17-2010, 08:08 PM   #5
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QuoteOriginally posted by ckusnierek Quote
Is there any reading that would explain the relationship between DOF/Aperture/and Focal Length?
Do you want it the hard way or the easy way?

Here's the Wikipedia entry on DOF.

The easy way: DOF is the range of distance from the lens where objects look to be in focus. Several variables are involved, but we can simplify it as:

* The shorter the focal length and/or the smaller the aperture, the thicker the DOF
* The longer the focal length and/or the wider the aperture, the thinner the DOF

Lens-to-subject distance is also a factor, as is the way the image is presented, and how good your eyeballs are. See the Wikipedia entry for details.

You'll hear about razor-thin DOF. That comes from fast (wide aperture) longer-than-normal lenses. Wide-angle (short focal length) lenses, with the aperture stopped down, may have seemingly infinite DOF.

And that's the short version. Have fun!
04-17-2010, 08:26 PM   #6
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That would explain why I did have a razor thin DOF at 300mm /F5.6

At F5.6 I was not even able to get one flow in focus. Heck at F32 the far left one still of not 100%
04-17-2010, 08:50 PM   #7
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QuoteOriginally posted by ckusnierek Quote
That would explain why I did have a razor thin DOF at 300mm /F5.6

At F5.6 I was not even able to get one flow in focus. Heck at F32 the far left one still of not 100%
That's because the longer the focal length that you're shooting at, the narrower the DOF is naturally (because of the focal plane shrinking with the longer focal length). Try going out one day and setting your camera on something and taking a photo of a grassy or flowery field. First do it with a 50mm lens at f/5.6 and see which flowers are in focus and how many of them there are, then go out and do the same thing with a lens at 300mm f/5.6 and see how many there are.
04-17-2010, 10:22 PM   #8
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QuoteOriginally posted by ckusnierek Quote
The only reason I used such a high aperture was because I was having trounle getting all the petals of all three flowers in focus.
It is not always necessary to have all three flowers in focus. If one of them is the main subject, that's the one that must be in focus. But that is a personal thing. If you want all three in focus, then that is it.

Below a link to an online DOF calculator. Select your camera, focal length, aperture and distance and it calculates what will be in and out of focus.

Online Depth of Field Calculator

PS: I like the picture

04-17-2010, 10:47 PM   #9
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QuoteOriginally posted by ckusnierek Quote
Is there any reading that would explain the relationship between DOF/Aperture/and Focal Length?

Also Bryan Peterson's "Understanding Exposure". Good read.
04-18-2010, 01:39 AM   #10
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QuoteOriginally posted by sterretje Quote
QuoteOriginally posted by ckusnierek Quote
The only reason I used such a high aperture was because I was having trounle getting all the petals of all three flowers in focus.
It is not always necessary to have all three flowers in focus. If one of them is the main subject, that's the one that must be in focus. But that is a personal thing. If you want all three in focus, then that is it.
As mentioned in the Wikipedia article, techniques exist for extending DOF. Note "focus stacking", where a number of shots are made with slightly different focus, then combined in software. It's not a beginner's technique, but it's there. Much technical-scientific macro work DEMANDS an expanded DOF, so that details of a subject under study are clearly visible. I'll see if I can dig up some current guides to such work.

QuoteQuote:
Below a link to an online DOF calculator. Select your camera, focal length, aperture and distance and it calculates what will be in and out of focus.
I have used this calculator and found it to be quite erroneous, especially when dealing with close-up photography. Plug in some values and see what happens. It's pretty funny, like when you tell it your subject distance is 10cm (4 inches) and it returns a hyperfocal distance of 950cm (~32 feet).

PS: I like the picture too.
04-18-2010, 05:04 AM   #11
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QuoteOriginally posted by RioRico Quote
As mentioned in the Wikipedia article, techniques exist for extending DOF. Note "focus stacking", where a number of shots are made with slightly different focus, then combined in software. It's not a beginner's technique, but it's there. Much technical-scientific macro work DEMANDS an expanded DOF, so that details of a subject under study are clearly visible. I'll see if I can dig up some current guides to such work.



I have used this calculator and found it to be quite erroneous, especially when dealing with close-up photography. Plug in some values and see what happens. It's pretty funny, like when you tell it your subject distance is 10cm (4 inches) and it returns a hyperfocal distance of 950cm (~32 feet).

PS: I like the picture too.
Yea, focus stacking is a really great way to expand your depth of field. I have done it with adobe photoshop CS4 and it really is amazing the photos that you can come up with. However, adobe photoshop is very expensive and I only got to use it because my friend was able to get a copy from his college for like dirt cheap so he had to go for it.

I too have used this calculator and I agree with Rio, I have found that it does give some wrong answers and it sometimes really off as well. On some of my older lenses there is actually a depth of field scale right on the lens barrel which is normally very helpful. I would do some more research online and see what you can come up with and see if that can help you out.
04-18-2010, 05:45 AM   #12
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QuoteOriginally posted by Tuner571 Quote
I have done it with adobe photoshop CS4 and it really is amazing the photos that you can come up with. However, adobe photoshop is very expensive and I only got to use it because my friend was able to get a copy from his college for like dirt cheap so he had to go for it.
I have CS4 and will have a seat of CS5 once released
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