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03-25-2009, 01:04 PM   #1
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Depth of field "problem"

I was reading a thread on the pentax forum when suddenly I got a little friend on my computer screen:

100% crop

And since I hate spiders I had to defend myself using my quite new K20D. I hunted my new little friend down onto the computer desk and it landed on a piece of paper where the photo was taken. Since the light was very bad I had to use the flash and I then tried to relocate my friend to a more well lighted place. He didn't like my idea at all and jumped down on the floor where I ran back and forth a while taking photos untill he escaped under my couch . I then went back to the computer and downloaded the pictures.

Then I noticed that my photos wasn't in the condition I would have wanted them to be. As you can see on the photo one of the right legs and the "head" of the spider got nice details but the rest is not in focus. I took the photo using my K20D with Pentax SMC DA 35/2.8 Limited Macro. The camera was on f/2,8 1/45s ISO 100 using flash.

Should I have used a bigger aperture to get longer depth of field to get a more detailed photo or how would you do it? When I saw the photos I wanted to try some more setting on my little friend, but he still haven't crawled out from under the couch

03-25-2009, 04:48 PM   #2
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Yes a smaller aperture would help, but of course that lowers your shutter speed, so up your ISO. The problem with being really close to things is a narrow depth of field.
03-25-2009, 05:28 PM   #3
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When you're shooting something that small, you really have to be set up for macro, and on a tripod.

You should have Crazy-Glued his legs (2 legs minimum) to a sheet of paper and really taken your time to set up.

If you only glue 2 legs, he would move around a lot and you would need a fast shutter speed. Glue all 8 and you're perfect to go!
03-25-2009, 05:34 PM   #4
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Yes, an aperture of f/4 or 5.6 would probably be enough DOF to put your little friend fully in focus while still leaving the paper & background blurred. But then you'd have to increase your ISO to compensate for the effect the 1-2 stop reduction would otherwise have on your shutter speed.

But FWIW, I really like the effect that your f/2.8 had. It makes an otherwise ordinary picture of a spider quite a bit more interesting.

03-25-2009, 10:57 PM   #5
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QuoteOriginally posted by Stickannn Quote
Should I have used a bigger aperture to get longer depth of field to get a more detailed photo or how would you do it?
Just to clear up any potential confusion, you need to use a SMALLER aperture (ie, choose a setting where the diaphragm blades make a smaller "hole") to get more depth of field. The confusion stems from the use of f/numbers to measure aperture - this means a larger f/number gives you a smaller aperture (ie, f/11 has a smaller diaphragm opening than f/8).

Despite the fact that the "11" in "f/11" is a bigger number than the "8" in "f/8", a lens set to f/11 is said to have a smaller aperture than one set to f/8 (other factors being equal).
03-25-2009, 10:58 PM   #6
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QuoteOriginally posted by Ira Quote
You should have Crazy-Glued his legs (2 legs minimum) to a sheet of paper and really taken your time to set up.
Is that really how people get insect macros?
03-26-2009, 05:15 AM   #7
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QuoteOriginally posted by Sean Nelson Quote
Is that really how people get insect macros?
I've heard of people putting insects in the freezer for a little while before shooting them, but never of anyone using Crazy-Glue !
03-26-2009, 07:24 AM   #8
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QuoteOriginally posted by indytax Quote
Yes, an aperture of f/4 or 5.6 would probably be enough DOF to put your little friend fully in focus while still leaving the paper & background blurred. But then you'd have to increase your ISO to compensate for the effect the 1-2 stop reduction would otherwise have on your shutter speed.

But FWIW, I really like the effect that your f/2.8 had. It makes an otherwise ordinary picture of a spider quite a bit more interesting.
He was using flash at very short distance. I don't think any ISO increase would have been necessary.
QuoteQuote:
Then I noticed that my photos wasn't in the condition I would have wanted them to be..............I took the photo using my K20D with Pentax SMC DA 35/2.8 Limited Macro. The camera was on f/2,8 1/45s ISO 100 using flash.


03-26-2009, 09:32 AM   #9
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QuoteOriginally posted by Ira Quote
When you're shooting something that small, you really have to be set up for macro, and on a tripod.
Unfortunately I don't own a tripod yet, but I'm planning of buying one in the near future. But since I got my little visitor at my disposal I wanted to try a few macro shots on him.

QuoteOriginally posted by Sean Nelson Quote
Just to clear up any potential confusion, you need to use a SMALLER aperture (ie, choose a setting where the diaphragm blades make a smaller "hole") to get more depth of field.
I understand how the camera work with the diaphragm blades, but as you point out I was a little confused what to call it in text . Thanks for clearing that up for me!
03-26-2009, 10:05 AM   #10
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QuoteOriginally posted by Parallax Quote
He was using flash at very short distance. I don't think any ISO increase would have been necessary.
Ah, missed that. Thanks for pointing that out. That makes it even better, and easier.
03-26-2009, 11:57 AM   #11
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And if you're using flash, just lock the shutter speed at 1/180s. The flash will be able to fully illuminate that subject, no need to get ANY ambient light into the shot.

I would have gone f/11, 1/180s, ISO400.
03-26-2009, 01:45 PM   #12
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I was going to suggest the freezing idea too...had a (unmarried) friend who did this.
03-26-2009, 02:01 PM   #13
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QuoteOriginally posted by egordon99 Quote
And if you're using flash, just lock the shutter speed at 1/180s. The flash will be able to fully illuminate that subject, no need to get ANY ambient light into the shot.

I would have gone f/11, 1/180s, ISO400.
Care to explain the 1/180s ISO400? I used 1/45 since the camera want's that when using flash. 1/180 @ f/11 and you only get the flash light in the photo? and then up to ISO400 to not get it underexposed?
03-27-2009, 05:23 AM   #14
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I'm not sure how powerful the built-in flash is, but I took a guess that you would need ISO400 to get enough flash power at f/11.

Like I said, 1/180s, f/11, ISO400 indoors will most likely make the shot completely black without flash, so the flash pulse will provide all the illumination for you.

When you say "I used 1/45 since the camera want's that when using flash", are you using P mode? Don't....Use Manual mode for flash.
03-27-2009, 05:24 AM   #15
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This is for an external hot shoe flash, but most of it still applies to the built-in flash (except you obviously can't bounce it and you don't have HSS)

Basically, with flash, the FLASH exposure is solely determined by flash power (actually duration, how long the bulb is actually firing for), aperture and ISO. Ambient exposure is determined by ISO, shutter speed, and aperture (just like without any flash), so the trick is balancing the two. If I'm indoors in a smallish room (such as in someone's house), I usually just forget about ambient since the flash is powerful enough to light up the entire room (hence the 1/180s below, if the flash didn't fire, I'd have a more or less black picture) Now although you're shooting MANUAL Mode, that's only for the ambient exposure (the exposure needle in the viewfinder will blink warning you about underexposure, but ignore that). The camera's P-TTL metering will determine the needed flash output for a proper exposure.

Here's something I wrote on another forum -
"Easy" recipe for great P-TTL flash shots -
1)Point flash at ceiling
2)Put camera in MANUAL mode on the mode dial
3)Set FEC to +1 on the flash head

4)Shoot RAW (this allows you to recover some highlights that might get blown as a result of #3 above)

5)Set ISO to 200 (to start)
6)Set shutter speed to 1/180s
7)Set f-stop to whatever DOF you want


Now if the flash runs out of "power" because of high ceilings, you can raise the ISO or open up the f-stop to compensate. Or you can slow down the shutter to bring more ambient light into the exposure (in addition to adjusting ISO/f-stop) If the ceiling is REALLY high (like in a church), you may need a reflector to throw some of the light forward (I use the Joe Demb Flip-it).

Quick and dirty outdoor fill flash tutorial -
Basically, if your subject is in shade and the background is bright (ie under a tree) or majorly backlit, fill flash is your friend. Think of those times when you got a properly exposed background, but the subject was almost pitch black.

Put camera into Av mode, metering will set the shutter speed to expose the overall shot (which in the situations that call for fill-flash will generally be the background) based on your selected aperture/ISO.
Make sure flash is set to HSS (in case your shutter speed go faster than 1/180s) and P-TTL. Fire away! The shutter speed/f-stop/ISO will expose the background, and the flash should output enough power to light up the foreground.

Now to control the background exposure, you use exposure compensation on the camera body (which would adjust the shutter speed), to adjust how much fill for the flash exposure, you use Flash exposure compensation. The trick is balancing the two (as it is with indoor work), and that comes with experience/experimentation.
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