New to Digital cameras

Techniques and equipment.

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Postby Dane » Jan 25, 2007 8:41 am

On this shot, I used a lower f-stop (3.8?) and a 15-sec shutter opening. DoF seems good to my novice eye.
As SB pointed out, this is with multiple flashes from each side of the frame.
I find it amazing compared to my usual point-and-shoot results!
(this is from the same trip that SB led BrianC on)

Image
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Postby bigalpha » Jan 25, 2007 9:52 am

paul wrote:
The light can be varied by a type of filtration affecting the sensitivity of the CCD. Depth of field is a consequence of the size of the hole (and hence area of lens) through which the light passes - so quite often varying the f-stop on digital cameras has no effect on depth of field.


So, what you are saying, is that a lot of digital cameras don't actually have an aperture; that the sensitivity of the CCD just changes?
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Postby Dane » Jan 25, 2007 10:22 am

BTW, I should mention that my shot was not w/ a Canon A650, but an Olympus D595 - an older and probably less sophisticated pocket camera.
Still, I was very pleased with the results and really appreciate Spelunker Bob's help and guidance and Brian's company and enthusiasm.
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Postby paul » Jan 25, 2007 3:04 pm

bigalpha wrote:
paul wrote:
The light can be varied by a type of filtration affecting the sensitivity of the CCD. Depth of field is a consequence of the size of the hole (and hence area of lens) through which the light passes - so quite often varying the f-stop on digital cameras has no effect on depth of field.


So, what you are saying, is that a lot of digital cameras don't actually have an aperture; that the sensitivity of the CCD just changes?


Sort of.

I have a 3 year old Nikon Coolpix 4300 (it may have been sold under a different name in the States)

From the manual "Filter is applied to adjust the light entering the camera when the aperture is set to its minimum wit the COOLPIX 4300. Because of this, the minimum aperture setting may not yield wider depth of field as expected from the aperture value displayed in the monitor".

So I guess the same thing possibly also applies to some other compact digital cameras...
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Postby bigalpha » Jan 25, 2007 3:19 pm

Paul -

Is there a way to test this with a newer digital camera? My manual doesn't say anything about the aperture setting and DOF.

I'd like to see if my camera will actually give me a wider DOF, and not just filter the light.
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Postby BrianC » Jan 25, 2007 9:56 pm

I do remember when we were setting up the shots we set shutter speed to 15 seconds with f2.8, then when I would zoom the shutter speed would stay at 15 sec but the f stop would automatically show higher number creating smaller aperture. also if I tried to set the f stop even higher (decreasing aperture even smaller) the picture taken would blurr as out of focus and the camera would show +-2 I guess it must be saying I shouldn't do this as the results would blurr! I didn't think about this until after the trip :doh: I guess that is part of the learning curve! Spelunker Bob, Sounds like we need another photo trip to try out my new found knowledge! Dane your pic is awesome,and all of you here are great with this wonderful advice.
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Postby SpelunkerBoB » Jan 26, 2007 12:16 am

Yes, that was a great picture Dane - nice composition. Maybe we can get out for another session in the next couple of weeks.
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Postby paul » Jan 26, 2007 2:30 am

bigalpha wrote:Paul -

Is there a way to test this with a newer digital camera? My manual doesn't say anything about the aperture setting and DOF.

I'd like to see if my camera will actually give me a wider DOF, and not just filter the light.


I presume you can set the camera's shutter speed manually and allow the camera to automatically set the aperture?

You could try taking a close-up photo of something with objects in the backround some distance away with the flash turned off. I'm talking about say a head and shoulders shot of someone outside with a background some distance away, with some sort of object or objects only a few feet or so behind.

Focus on the head and set the shutter speed to a slow setting (say 1/30 or 1/60 or thereabouts) and then take the photo. The aperture setting should be smaller (larger f-stop) due to the slower shutter speed.

Now set the shutter speed to a faster setting (1/250 or 1/500 or so) and repeat the photo. Because the shutter speed was faster, in order to allow more light in, the aperture will have to be larger (smaller f-stop).

Compare the two photos. If in the case of the faster shutter/larger aperture (smaller f-stop) the background is more blurred than the first photo, you know that the camera actually has an iris and the aperture is affecting the depth of field.
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Postby NZcaver » Jan 26, 2007 4:10 am

paul wrote:Also many digital cameras so not actually use an iris to control the amount of light entering the camera as on film cameras (related to the f-stop).

<snip>

From the manual "Filter is applied to adjust the light entering the camera when the aperture is set to its minimum wit the COOLPIX 4300. Because of this, the minimum aperture setting may not yield wider depth of field as expected from the aperture value displayed in the monitor".

So I guess the same thing possibly also applies to some other compact digital cameras...

Interesting... so your camera has a filter that acts as a pseudo-aperture, complete with f-stop settings? Weird! Thankfully it appears your camera is in the minority when it comes to this feature.

My understanding is that the vast majority of modern digital cameras (excluding camera phones) have a *real* adjustable aperture, which can directly affect your depth of field. Now not all models are manually adjustable of course - but with those that are, you should be able to control your DOF. Those that aren't - well, the DOF might change a little, but unless you're shooting extreme close-ups it won't be anything to worry about.

Now it's also true that digital camera apertures are generally smaller than 35mm ones, because tiny digital CCDs call for shorter focal lengths. Therefore the aperture setting on your "average" digital camera often has a less profound effect on depth of field, when compared with a 35mm camera. Whew! Clear as mud? :big grin:

Here's a little further reading....
http://www.svca.org/articles/DigitalDepthofField.htm
http://www.wrotniak.net/photo/tech/dof.html

Good advice on testing DOF in your previous post, by the way. :wink:
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Postby Dane » Jan 26, 2007 7:23 am

Thanks guys, but SB deserves the credit - like Brian said, we just stood there and pushed the button!

As to DoF and f-stop, the zoom obviously affects the DoF, and to NZ's point, at least in my case, my options for f-stop were severely limited from the onset.

With a normal lens shot (no zoom), my options on f-stop were 2.8 or 4.6 I believe. I could get in-between f-stops by adjusting the zoom, but I couldn't go any higher. My thinking is that this represents a true aperture setting, vs digital filtering, showing the true limits of the CCD.

Of course, I just push the button, so what the hell do I know!!!!
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Postby Teresa » Jan 26, 2007 11:02 am

The lack of fast shutter speeds or a fast lens and the slow CCD is my one quibble with my digital camera. I've always had fast and good in low-light lenses in film cameras, but as yet, they are out of reach financially in digital.

Just got an Olympus FE-180 for Christmas. Lacks a settable white balance, and I'm still trying to interpret the 'Scene settings' into camera-speak-- i.e., Sports when I really want to stop action on a squirrel.

Other than that, I'm pretty happy for the price. They could have used a bigger built in flash, though. (Smaller than the D-535.) I guess I just carry my potato masher strobe for cave pictures.
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Postby NZcaver » Jan 26, 2007 12:58 pm

Teresa wrote:The lack of fast shutter speeds or a fast lens and the slow CCD is my one quibble with my digital camera. I've always had fast and good in low-light lenses in film cameras, but as yet, they are out of reach financially in digital.

Yep, shutter lag is a common digital complaint - although as time progresses the specs are getting better. If you want a near-instant shutter, then a DSLR is probably the type of camera for you. Expensive, yes - but slowly coming down in price.

I've been happy with Olympus cameras for a long time - from my old 35mm models to my current "midsize" caving mainstay the C-5050 zoom (which, by the way, has a good range of aperture settings but a substantial shutter lag). When the time came to get a new compact digital recently, I looked at the current Olympus models and came away disappointed. I researched several different brands, and even tested and returned a couple of models. I finally settled on a Canon A540, which I'm very impressed with. It has a fast startup time, a short shutter lag, and even manual aperture and shutter settings. However it's not my first choice for a caving camera, mainly due to the old flash/slave synchro issue mentioned earlier in this thread.
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Postby fuzzy-hair-man » Jan 28, 2007 7:17 pm

Teresa you can help shutter lag by (usually) half pressing and holding the button this asks the camera to evaluate the exposure and focus and whilst you have the button half held it stores them. When you go to take the photo the lag is shorter because the camera doesn't have to evaluate the exposure and focus it just takes the photo. Just make sure the light and focus hasn't changed too much since you half pressed the shutter button. :grin:
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Postby NZcaver » Feb 6, 2007 7:35 am

Correction to my previous post... :oops:

NZcaver wrote:When the time came to get a new compact digital recently, I looked at the current Olympus models and came away disappointed. I researched several different brands, and even tested and returned a couple of models. I finally settled on a Canon A540, which I'm very impressed with. It has a fast startup time, a short shutter lag, and even manual aperture and shutter settings. However it's not my first choice for a caving camera, mainly due to the old flash/slave synchro issue mentioned earlier in this thread.

Actually I can set my Canon A540 to single flash, so it will fire a regular slave unit. :kewl:

Image

There's a good chance this might work with some of the other Canon models too. All I did was set the mode to manual exposure, selected my shutter speed and f-stop, and turned the flash on. The camera even gave me the option to set the flash for 1/3, 2/3, or full power. I set up one of my slave flashes, hit the shutter, and bingo - success! I tried all the other modes (auto, aperture priority, shutter priority, nightime mode, etc) but manual exposure is the only one that gives a true single flash. Guess I should really read the camera manual one of these days. :wink:


Since I was on a roll, I also tested the depth of field on the A540. Zoomed in all the way (23mm - aka 4 times zoom) the widest f-stop I can select is 5.5, and the smallest is f8. My test frame included subjects from about 0.3m to 5m away, and the result was a slight but noticeable difference in DOF. Zooming out all the way (6mm), I then compared shots at f8 and f2.6 (widest aperture) in the same room. The difference in DOF was again quite noticeable, but doesn't give the same control I get with my larger C-5050 Zoom or an SLR.

Conclusion - the little A540 does have some form of aperture that affects depth of field. I'd post the photographic evidence, but the test shots aren't very interesting - they were taken above ground. Oh and FYI, Canon make a waterproof housing for this camera too. Another item to put on the wish list... :big grin:
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Postby MoonshineR DavE » Feb 8, 2007 4:08 pm

I may have missed it somewhere in the posts but does the a630 have a bulb setting or is 15 sec. as long as the shutter will stay open. I am planning on getting one very soon and was wondering if I need a couple of fireflys.
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