Forgot Password
Pentax Camera Forums Home
 

Showing results 1 to 25 of 168 Search:
Forum: Digital Processing, Software, and Printing 02-22-2009, 03:34 PM  
PhotoME problem...
Posted By baw
Replies: 6
Views: 2,957
Works ok here. Perhaps you did some editing on your images? This could strip the Maker Notes.
Forum: Photographic Technique 12-29-2008, 08:16 AM  
How to take pictures that are sharp throughout ?
Posted By baw
Replies: 17
Views: 4,633
Have a look at this article. Basically, focus at the things in the background you need to be sharp. The aperture decides what in the foreground will be acceptably sharp.
Forum: Pentax Camera and Field Accessories 12-18-2008, 11:30 AM  
GPS for image id and its operation
Posted By baw
Replies: 29
Views: 4,424
Our EFB's are fixed and integrated with the FMS's. Pretty neat.
Since this is going way of topic here is an image.
Forum: Pentax Camera and Field Accessories 12-18-2008, 09:18 AM  
GPS for image id and its operation
Posted By baw
Replies: 29
Views: 4,424
Yep, Holux GPSlim 236 with BT.
Feeds a T-Mobile MDA running Windows Mobile.
Forum: Pentax Camera and Field Accessories 12-18-2008, 06:46 AM  
GPS for image id and its operation
Posted By baw
Replies: 29
Views: 4,424
But I do like this Airport Map function on the EFB, certainly in very low visibility. :cool:
Forum: Pentax Camera and Field Accessories 12-18-2008, 03:28 AM  
GPS for image id and its operation
Posted By baw
Replies: 29
Views: 4,424
In the geotagging software I've seen you can add a correction to the gps log times. So it's not really necessary to have both camera and gps in sync. It doesn't hurt either :D
Simple trick: take a shot of your gps device showing the time. When geotagging at home you have this time + the EXIF time of that image. Use the difference as correction in your software.
Forum: Pentax Camera and Field Accessories 12-17-2008, 12:03 PM  
GPS for image id and its operation
Posted By baw
Replies: 29
Views: 4,424
Hi Daniel

I use the same Holux GPS you have. It feeds a navigator on my mobile phone.
It also drives a program that creates a GPX file I use to automatically Geotag my images.
Have a look at this thread.

To see how geotagged images can be used, have a look at the "Geotag Demo" album on my website (signature). (you need to have Google Earth installed)
Forum: Digital Processing, Software, and Printing 10-31-2008, 12:18 PM  
Poll: Q for RAW shooters
Posted By baw
Replies: 80
Views: 16,491
Shoot PEF, download as DNG into Lighroom.
Any edits will be written into the DNG preview image.
My DAM software (iMatch) reads this preview and displays the edited version as thumbnail.
For the moment I still keep the PEF's.

For web publishing, printing etc. I use the DNG and convert as needed.
Forum: Photographic Technique 10-07-2008, 07:32 AM  
DOF
Posted By baw
Replies: 50
Views: 8,842
I still had this Excel sheet on my harddisk.
All distances are calculated using DOFMaster.
For those of you still interested:





Code:

Distance from lens where diff. CoC's originate from.		

Both lenses focussed at 10m.



CoC (mm) 25mm f/2 100mm f/8



0.12 2.1 5.1

0.11 2.2 5.3

0.10 2.4 5.6

0.09 2.6 5.8

0.08 2.8 6.1

0.07 3.1 6.4

0.06 3.4 6.8

0.05 3.9 7.2

0.04 4.4 7.6

0.03 5.1 8.1

0.02 6.1 8.6

0.01 7.6 9.3



0.00 10.0 10.0



0.01 14.7 10.9

0.02 27.7 11.9

0.03 235.8 13.1

0.04 infinity 14.6

0.05 infinity 16.6

0.06 infinity 19.1

0.07 infinity 22.4

0.08 infinity 27.3

0.09 infinity 34.8

0.10 infinity 48.1

0.11 infinity 77.6

0.12 infinity 210.6



Compare CoC 0.01 for 25mm vs. 0.04 for 100mm
Or 0.02 vs 0.08 or 0.03 vs 0.12
Forum: Photographic Technique 10-06-2008, 03:31 PM  
DOF
Posted By baw
Replies: 50
Views: 8,842
I feel the DOF concept isn't overly complex, especially if you separate the optical and the imaging/viewing part.
Optical results in CoC's on the sensor/film, imaging/viewing in a CoC limt, that decides which CoC's fall within DOF.

That's the gist of the "Back to the basics" post above. I'm interested in comments pro or contra this post to see if I have to change something in my reasoning :(

In practice you may be interested in this concept. It's a bit different from the hyperfocal focussing thing: focus on the background and stop down as needed to resolve foreground objects. useable for landscapes etc.

Problem with the DOF preview button to me is the small size of the LCD screen. Allmost everything seems to be sharp on that screen (or in the viewfinder, but then everyhing turns allmost dark when stopping down.
Forum: Photographic Technique 10-06-2008, 03:13 PM  
DOF
Posted By baw
Replies: 50
Views: 8,842
Since we need both terms in a discussion of DOF it's less confusing to use the correct terms. You're talking about CoC limit (or maximum permissable CoC)
From the Wikipedia article:

The CoC limit can be choosen freely depending on your needs. If you print all your images at poster size, you'd better use a small value for CoC limit to prevent disappointing prints.
Sensor format in itself does NOT influence DOF.
The smaller sensors have shorter focal length lenses to get comparable FOV as larger format cameras.
If you need large DOF, use a P&S, especially for macro.
Well, shorter focal length has larger DOF, keeping all other parameters the same.
Forum: Photographic Technique 10-06-2008, 04:10 AM  
DOF
Posted By baw
Replies: 50
Views: 8,842
I'm not sure what you mean with "acceptable focus". DOF is about looking at an image and deciding what is acceptably SHARP to you. Back to the scene to measure the distance from your lens to objects at the edge of acceptable sharpness, and you have DOF.
Optical physics gives us a measurable quantity: CoC. (All those tiny circles your lens projects on the sensor/film.)
To calculate DOF you use a maximum for those CoC's: CoC limit.
The CoC limit depends on the whole viewing traject: magnification from sensor to final image, viewing distance, visual acuity etc.etc.
Forum: Photographic Technique 10-06-2008, 03:56 AM  
DOF
Posted By baw
Replies: 50
Views: 8,842
I'm not sure I follow you here.
Using the same lens and settings, printing with a magnification of lets say 10x, FF will print as a 24x36cm image and APS-C as a 16x24cm image.
DOF for both will be exactly the same since the same objects will be acceptably sharp in both images. Only when magnifying the APS-C image to the same size as FF DOF will change, due to the larger magnification.
Forum: Photographic Technique 10-06-2008, 03:34 AM  
DOF
Posted By baw
Replies: 50
Views: 8,842
First I gave this example to show that by changing enough parameters you can demonstrate just about anything. To see the effect of a parameter only change that parameter and keep everything else the same.
I was initially also sceptical when I saw something like in my example. Dialing the numbers in a DOF calculator did work out though. I then checked the above example for several settings, and it still holds.
Have a look at these images.

To check my example, use DOFMaster. It has the option to select a CoC limit iso camera.
Just use a 4 x higher CoC limit for the 100mm because you magnify the 25mm crop 4 times. so .001 and .004 or .002 and .008 etc.
Forum: Photographic Technique 10-05-2008, 12:33 AM  
DOF
Posted By baw
Replies: 50
Views: 8,842
This thread seems to raise more questions than it answers. I'll try to summarise my take on DOF.

First the definition: DOF is the range of objectdistances from the camera in your scene , within which objects will be judged as acceptably sharp when viewed in the resulting image.
See this page for some similar defintions.
As an example take the image with the domino stones on that page. I find the stones 4,5 and 6 (with 3 black dots) acceptably sharp.
Now back to the scene and measure the distance from your lens to stone 4 and stone 6, and you have the DOF.
That's basically what DOF is all about.

To give this a more theoretical framework the following:


The optical part.

Our lenses can't project everything in a scene equally sharp. To quantify this the Circle of Confusion (CoC) has been introduced. Points in the scene that are not at the focussed distance will be projected by the lens on the imaging plane behind it as circles (CoC's). The size of these circles depends on focal length, f/stop (relative aperture) and focussed distance of the lens plus the position of the point in the scene.
See this page for a nice illustration.

The imaging/viewing part.

We define DOF by choosing a maximum size for all those CoC's, the CoC limit.
The CoC limit depends on a lot of factors in the imaging/viewing process, ao the sensor resolution, magnification, viewing distance, visual acuity, lighting conditions etc. etc.
You should decide on a CoC limit for your particular imaging /viewing situation.

DOF.

For each point in the scene the CoC diameter is known.
CoC diameter > CoC limit: outside DOF
CoC diameter < CoC limit: inside DOF

Comparing different situations.

Discussions around DOF usually are about the effect of a certain parameter.
The only way to show this effect is by keeping all other parameters the same.
To show the effect of different lens settings, keep the imaging/display part the same by eg. viewing all images on the same monitor at full screen. Now change only the parameter you are interested in.
You'll find that focal length, f/stop and focussed distance all influence DOF.
By changing 2 or more parameters, you can create images that look (or even are) the same, but you can't conclude that this is due to the changing of a single parameter.

Some examples

Sensor size.
For different sensor sizes you end up with different sized images, having the same DOF.
Now if you compare different sensor sizes at the same image size, you'll see different DOF's, but this is due to different magnification to arrive at the same image size.

Constant magnification ratio.
You'll find claims that DOF is independant of focal length when keeping the magn. ratio the same.
This is usually shown with two images shot at different focal lengths showing the same scene.
What happens here is that for the different focal lengths to give the same magn. ratio you need to change the object distance and thus the focussed distance as well. You change TWO of the DOF parameters.
Also perspective is different.
At macro distances the comparison won't hold, same for distances where the focussed distance isn't small in relation to the hyperfocal distance. Lastly the distribution of the DOF in front and behind the focussed distance isn't constant.

Last example.
You can create equal images with exact same DOF for different focal lengths by chosing your settings carefully.
eg. a 25mm lens at f/2 and a 100mm at f/8. Focus at eg. 10 meter.
When cropping the 25mm image to have the same scene as the 100mm one and then magnifying it 4 times, you'll have two identical images, even the same perspective, but you had two change 3 parameters to create this result.

Finally.
In the above I didn't mention several assumptions/simplifications to keep the text readable.
eg. diffraction, CoC's looking like cat's eyes or having the shape of the diaphragm blades, sensors having enough pixels for large magnification etc.
Forum: Photographic Technique 10-04-2008, 07:07 AM  
DOF
Posted By baw
Replies: 50
Views: 8,842
Sorry John, but it's back to the drawing bord :eek:

Magnification, viewing distance, visual acuity, lighting conditions etc. all influence DOF. Remember DOF is about the portion of the viewed image that is ACCEPTABLY sharp. Just putting on your glasses when viewing an image does change DOF, because you'll find less of the image to be acceptably sharp than without glasses.
Forum: Photographic Technique 10-03-2008, 12:53 AM  
DOF
Posted By baw
Replies: 50
Views: 8,842
Even if the same objects appear to have the same sharpness and the same size in both images, DOF is different because DOF is a range of distances from your camera.

Realise that with this setup you change about every variable that influences DOF:
focal length, focussed distance and magnification from captured to displayed image. About the only thing that remains the same is f/stop (relative aperture) :)
Forum: Photographic Technique 10-03-2008, 12:44 AM  
DOF
Posted By baw
Replies: 50
Views: 8,842
I think I'm getting the point. Since DOF is a range of distances from of the lens, DOF is wildly different in these two cases. Same objects will appear with approximately the same sharpness in this case.
In other words: the range of acceptable sharpness around the focussed object is approximately the same. This will only hold when the focussed distance of both lenses is small in relation to their respective hyperfocal distance.
Also perpective is different.
Forum: Photographic Technique 10-02-2008, 06:28 AM  
DOF
Posted By baw
Replies: 50
Views: 8,842
The two focal lengths, f/stop and an estimated focussed distance, like 1 meter for the 50mm and 2 meter for the 85mm lens. Using a maxCoC like 0,025mm you'll find that the range of acceptable sharpness around the same focussed object for both lenses is practicaly the same, so no surprise that the DOF in both images look the same as well.
Concluding that the focal length has no influence on DOF based on these two images makes no sense to me.
Forum: Photographic Technique 10-02-2008, 06:21 AM  
DOF
Posted By baw
Replies: 50
Views: 8,842
Sorry, I should have stated that I feel I have a grip on this whole DOF thing :confused:
Forum: Photographic Technique 10-02-2008, 06:18 AM  
DOF
Posted By baw
Replies: 50
Views: 8,842
If you leave everything else the same going from eg FF sensor to APS-C size sensor, you'll end up with a smaller image (crop factor ;) ), but the exact same DOF.
If you print/view the APS-C image at the same size as the Full frame image, you change the magnification as well, and consequently the DOF.

(with everything else the same I mean: same lens and settings, same sensor resolution!!, magnification, viewing distance etc.etc.)
Forum: Photographic Technique 10-01-2008, 03:50 PM  
DOF
Posted By baw
Replies: 50
Views: 8,842
In this post I reacted on some statements by Wheatfield.
Since it seems he isn't going to answer, and the subject is more suited for this forum here are my questions again:

Seems you have invented a whole new defintion of DOF. Perhaps you can explain what the relationship is. It's also unclear to me what you mean with reproduction ratio.

Perhaps someone can enlighten me?

On the test with the 50 and 85mm lenses by Stevebrot the following:
if you dial the numbers in a DOF calculator, you'll find the DOF to be allmost the same (within a few centimeters), so concluding that DOF isn't depending on focal length based on this test doesn't make sense to me.
Forum: Pentax DSLR Discussion 09-29-2008, 01:51 AM  
Perspective vs. FOV
Posted By baw
Replies: 34
Views: 6,597
Seems you have invented a whole new defintion of DOF. Perhaps you can explain what the relationship is. It's also unclear to me what you mean with reproduction ratio.

DOF is normally defined as a range of distances in front of the lens within which objects are reproduced ACCEPTABLY sharp in the resulting image.
See this page with a number of similar definitions and references.
Forum: Pentax DSLR Discussion 09-27-2008, 09:02 AM  
Perspective vs. FOV
Posted By baw
Replies: 34
Views: 6,597
I'm fine with a statement like: For a given FOV DOF is the same for different focal lengths. At least it seems to be so.
My point is that the article clearly implies that DOF is independant of focal length, which is nonsense.
I'm a bit surprised by this article. I had a high regard for Luminous Landscape....
Forum: Pentax DSLR Discussion 09-27-2008, 12:50 AM  
Perspective vs. FOV
Posted By baw
Replies: 34
Views: 6,597
These quotes from the article certainly give the impression that the author is stating that wide angle lenses do NOT have greater DOF than telelenses.
He tries to proof his point by changing focal length AND focussed distance.
As stated above, when changing aperture as well you can show that telelenses have more DOF than wide angle lenses. Not a very realistic approach imo.
Search took 0.01 seconds | Showing results 1 to 25 of 168

 
Forum Jump


All times are GMT -7. The time now is 08:07 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top