Go Back   Steve's Digicams Forums > Digicam Help > General Discussion

Reply
 
Thread Tools Search this Thread
Old Jan 15, 2004, 6:19 PM   #11
Member
 
Join Date: Jan 2004
Posts: 31
Default

JimC,

Good reading,thanks again.

The items will be mostly internal parts of a gas turbine engine...for example:

a combustion liner which is round shaped 10" tall and 24" across we noticed is cracked more than normal (yes there are allowable limits for these things).We need to take a close up picture of it to email to the manufacturer for further evaluation.

Note: typical cracks that are obviously out of limits are around 3"+. I imagine most shots will be damage/cracks below that length.

Picture of damage/crack needs as much detail as possible to show contour,and depth (which we can locally measure with vernier calipers before taking picture)

This will be THE primary use of camera along with general everyday how-to pictures for new things not yet in maintence manuals.
Vermont is offline   Reply With Quote
Old Jan 15, 2004, 7:04 PM   #12
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

OK... If I understand you correctly, the main cracks you'll need to photograph are not the obvious ones (3 inches long or greater), but the smaller ones. Is that right?

How deep are the cracks?

Will the photos be printed? If so, at what size (to you want to have a print large enough to show extremely fine detail of a small crack)?

Here are the potential problems:

*Depth of Field

With most inexpensive digital cameras, you may not have the ability to control aperture to allow a greater depth of field. This becomes far more important at very close ranges. The closer to your subject, the lower the depth of field (distance from lens that will still be in focus). Cameras that let you vary the Aperture (like the CP 4500) can help. By selecting a smaller aperture (higher F-Stop), you get more depth of field for the same focal length and distance to subject.

Here's an example. Note that this photo was taken at F2.8 (where the autoexposure is going to set the aperture with many cameras in lower light). See how the top of the ring is in focus, yet the creases between the fingers are not (because at closer ranges, you have less depth of field):

http://www.pbase.com/image/24722527/large

If I were even closer (for example, taking photos of a small crack), or using zoom to reduce corner softness/barrel distortion, depth of field would be even lower.

With a camera like the Coolpix 4500, I could have used a smaller Aperture to allow more of the photo to be in focus. With most inexpensive digital cameras, you can't.

* Even Lighting/Flash Glare - Depending on the depth of the cracks, it may be difficult to evenly light it, without shadows and/or flash reflections. The human eye can easily see when there is a substantial difference between brightness of a subject. A Digital Camera cannot (it has VERY limited dynamic range compared to the human eye, or even film).

That's why I suggested the Cool-Light SL-1 as a desired option.

* Corner Softness/Barrel Distortion -- Many cameras can only use macro at a set focal length (amount of zoom used). As a result, sometimes the outside portions of an image will be soft at very close ranges.

* Field of View - If you have a need to photograph tiny cracks, then print them at larger sizes, then a camera that can "fill the frame" with a small crack is desired. The Nikon Coolpix 4500 excels in this department.

*Ability of the Camera to Focus - If the surface is relatively uniform in color (no contrast), a Digital Camera will have problems focusing. Digital Cameras use a Contrast Detection Focus System. This means that it looks for vertical lines (with contrast) in order to accurately focus. There are some "tricks" you can use. For example: placing a needle on your subject, half pressing the shutter button, then removing the needle before pressing the shutter button down the rest of the way.

*Fast Enough Shutter Speeds to prevent Motion Blur without the use of a tripod indoors in lower light. If you need to use a smaller Aperture to improve Depth of Field, then the camera will need to use a slower shutter speed as a result. A device like the Cool-Light SL-1 can help with getting better illumination, without the problems associated with using flash (glare/flash reflections, shadows in the crack, etc.). Nikon's BSS (Best Shot Selector) can also help.

Let us know the answers to the above questions (Are most cracks going to be smaller? How deep are the cracks? Will the photos be printed? If so, at what size, and if you want to have a print large enough to show extremely fine detail of a small crack?)
JimC is offline   Reply With Quote
Old Jan 15, 2004, 8:42 PM   #13
Member
 
Join Date: Jan 2004
Posts: 31
Default

Average crack depths 1/16th" up to oh.......3/8"

Damage area (nicks,scores,raised metal,gauling) I am guessing no more than 3"


Photos will most likely not be printed out...just emailed. If they are going to be printed out it would be for corrective action presentations. ( what happened, how it happened ,what damage looks like-generally not needing to be too detailed)

I see what you mean by aperture with that picture. I have honestly been taking pictures since I was 20ish and never got into playing around with any of the f-stop/aperture stuff, just shutter/film speeds...lol

so your info is helpful and informative.....I'm learning also!

It is difficult to get so much info and process it about this camera. Most of the time our old fuji finepix is fired up and someone is trying to get a good enough shot to email (typically making numerous pictures). Our shop crew are not really digicam wizards by any means but I sure am learning a bunch.


I will see if I can find a picture at pbbase that might be sort of what we are going to be doing.


well,thanks Jim.
Vermont is offline   Reply With Quote
Old Jan 15, 2004, 8:43 PM   #14
Member
 
Join Date: Jan 2004
Posts: 31
Default

By the way, NICE HOUSE!!!!


haha...you got snow!

okay..found a few:

http://www.pbase.com/image/19519477

http://www.pbase.com/image/15801782

http://www.pbase.com/image/21189705

http://www.pbase.com/image/12717687
Vermont is offline   Reply With Quote
Old Jan 15, 2004, 9:13 PM   #15
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

Quote:
Originally Posted by Vermont
By the way, NICE HOUSE!!!!

haha...you got snow!
Actually, we're getting ready to put it on the market.

BTW, the last snow here was two years ago, and we didn't get much (just enough for my wife to make a small snowman).



Now, take a look at the last example you showed me. Note how as you get further away from the focus point, it gets much softer?

If you look at the EXIF, no flash was used. Shutter Speed was only 1/13 second, due to the Aperture being set to F8 to try and increase Depth of Field. So, they probably used a tripod.

This is the kind of problem you'll run into trying to take photos of a small area with most cameras. It probably won't be practical to use a tripod, yet if you have cracks 3/8" deep, you may have a very difficult time getting adequate depth of field without increasing aperture so much that shutter speeds may be too slow to prevent motion blur without a tripod (or using flash).

What's bright to the human eye, is not to the camera's lens -- especially when smaller apertures are used to improve depth of field at close range. Now part of the problem was that the photo was taken at full zoom. As focal length is increased, depth of field is decreased, so this could be helped some with a camera able to take macros at a greater variety of focal lengths.

You mentioned a Fuji. Some of the Fuji's have excellent macro ability, and throttle down their flash well at close range. Is that what you're using now? How does it work (what kind of problems are you having with it)? Do you get unwanted glare/reflections/shadows of the cracks?

BTW, note which camera was used for the photo of a pellet: A Nikon Coolpix 995. Again, the swivel bodied Nikons (Coolpix 950, 990, 995, 4500) have the best macro ability of any cameras "straight from the box".

I still think that's your best bet (Swivel Bodied Nikon + Cool-Light SL1). Although, you may be able to get by with a less expensive model, and cropping the photo for e-mail purposes.

The problem with shutter speeds too slow may be severe though, depending on lighting, and a flash may not throttle down well enough for shiny surfaces with many models (and too many reflections will destroy detail).
JimC is offline   Reply With Quote
Old Jan 15, 2004, 9:21 PM   #16
Member
 
Join Date: Jan 2004
Posts: 31
Default

I forget what model fuji we have....I will let you know after work tomorrow and see if I can get a picture of something with it.

Just to let you know.....no one in our shop is a "photographer".The pics I find might just be poor quality due to not setting it correctly.

Don't get me wrong....we DO need a new camera with higher resolution.

If I get time I will experiment with it.
Vermont is offline   Reply With Quote
Old Jan 15, 2004, 9:40 PM   #17
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

For e-mail purposes, and on screen viewing, higher resolution isn't needed.

Also, I could be overestimating the amount of detail you really need.

You may even be able to get by with a camera like the Minolta X20. It can capture an area of about 1.13 x 0.85 inches, and throttles down it's flash extremely well at close ranges. It's selling for under $200.00

You will have some corner softness/barrel distortion, but you could always capture a slightly larger area than the crack to make up for it.

It's a 2 Megapixel Camera (which is more than enough for on screen viewing).

Bear in mind that if you were using a camera that could only capture about 2 1/2 inches across, you'd need a camera with about 4 times as much resolution to see the same amount of detail (since you'd have twice the area as a camera like the X20 could capture, and it takes 4 times the resolution to double an image size). This is because resolution is composed of width x height.

However, it's Depth of Field would be somewhat limited at closest ranges. It is very small, and also runs off AA batteries.

So, you may want to try a camera like that first -- buying it from a vendor with a no restocking fee policy to see how well it works. Then, you could always return it for a refund and spring for something like the Coolpix 4500 + the SL-1 Macro Light if needed (for more even illumination without flash, more depth of field due to ability to control aperture, less barrel distortion since you could use zoom).
JimC is offline   Reply With Quote
Old Jan 16, 2004, 5:34 PM   #18
Member
 
Join Date: Jan 2004
Posts: 31
Default

The camera we have now is a Fuji Finepix MX700:

and Steve has a review on it (still have to read it)

http://www.steves-digicams.com/mx700.html

1.5 Megapixel.......maybe that is the problem of the poor pictures.

forgot to get sample picture....will try Saturday.
Vermont is offline   Reply With Quote
Old Jan 16, 2004, 6:23 PM   #19
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

Actually, from what I've been able to determine, from reading more than one review, it takes pretty darn good photos (just no optical zoom)

Don't get hung up too much on resolution. Chances are, it's 1.5 Megapixel Sensor produces images that are just as good (probably better, because it's sensor is less dense) compared to a Higher Resolution model for on screen viewing.

Bear in mind that it's 1280 x 1024 image is larger than most screen resolutions!

Make sure to set JPEG Quality to it's best mode (Fine), and it's resolution to 1280 x 1024.

Then, switch to Macro Mode (flower icon). It will focus as close as 3.5 inches in Macro Mode.

See how well this works first.
JimC is offline   Reply With Quote
Old Jan 23, 2004, 5:33 PM   #20
Member
 
Join Date: Jan 2004
Posts: 31
Default

Update 1/23/04:


Seems like the total cost for that 4500 will be a bit much considering we will need bigger memory card,macro light,travel bag,etc,etc,etc

I guess now I will work down the Nikon family and see how the others are for macro shots
Vermont is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 6:53 AM.