Serene Life

by garik

submit your photo


Hall of Fame
View past winners from this year

Please participate in Meta
and help us grow.

Tag Info

Hot answers tagged

48

Moire Fringe Method Use Bart van der Wolf's moire fringe method (also explained here and here, and archived here): It works by exploiting the interference patterns or moiré between the R/G/B LCD elements and the camera's LCD elements when directly viewed with Life View [sic]. With good optics and perfect focus, the moiré is maximized. ...


20

More than testing you should learn about your new lens. Although it is good to get some sanity checking first: Set up a flat target with sharp details that can cover the field-of-view of your lens. Set up your camera on a tripod pointing strait at the target. Repeatedly autofocus on your target and see if you can improve accuracy by manual focusing. If it ...


20

To check if your camera/lens is having front-focus or back-focus issues you can download a pdf (incl a focus chart) here: http://web.archive.org/web/20121205195820/http://focustestchart.com/focus21.pdf The first few pages describe how AF works and how it can be tested. The actual instructions for testing the AF start at page at page 13.


18

Please note that the following is a simplification of how things actually work Background: In digital photography, a light pattern is focused by the lens onto the image sensor. The image sensor is made up of millions of tiny light-sensitive sensors whose measurements are combined to form a 2-dimential array of pixels. Each tiny sensor produces a single ...


14

Here is the one we suggest using at SmugMug, the full sized image is available for anybody to use. http://cmac.smugmug.com/SmugMug/Test-prints/Calibration-prints/122238_UAxBs#5637776_3P7qj-A-LB


14

Contrast-Detect-vs.-Phase-Detect Adjustment Method I've been a huge fan of the moiré fringe method suggested by @Eruditass. But in playing with it, I discovered that there's an even better way, if your camera supports contrast-detect autofocus in live view mode. This is, in some ways, a combination of "method 1" and "method 2" of the moiré fringe approach, ...


11

There is a mathematical / measurement method to calculate the effective focal length of a lens by measuring its angle of view. The formula for angle of view is given as To calculate effective focal length (f), the formula comes down to: f = d / (2 * tan(α/2)) -> Equation1 Where d represents the size of the sensor in the direction measured. d would ...


11

There's quite a lot of different photographic flaws that you can test for. For each of these tests you may get different results at the widest angle compared to the longest zoom. Autofocus - Try setting up a high-contrast subject like a black & white test card and use autofocus from different distances while the camera is on a tripod to take shots. ...


10

You can measure the noise ratio at different ISO settings in a fairly simple way and use Gimp (Photoshop) to visualise the results. Below are the results with my camera, a Pentax K7. ISO 100 is used as the basis for comparison. The Noise Ratio is a dimensionless number showing the increased noise above that of ISO 100. If you photograph a perfectly ...


8

The Nyquist Limit is mostly used in digital sound recording, but it also applies to digital photography. In digital sound recording, the highest frequency sound that you can possibly record is half of the sampling frequency. A sound recording av 44100 kHz can not record any sound frequencies above 22050 Hz. In photography it means that you can't possibly ...


7

Fairly comprehensive, but easy to follow tips. How LensRentals.com tests lenses


6

Every time I accidentally bump my lens hood into a wall, my leg, a sign, or another person I am reminded of why I have a hood on my lens all of the time, even when there's not an obvious flare situation.


6

Testing autofocus is hard to get right, so it's a good question. I have used this chart with success: http://pentaxdslrs.blogspot.com/2008/06/part-1-autofocus-adjustment-for-pentax.html (It's a Pentax blog, but the chart and directions are general except for the interactions with the actual camera.) Follow the directions - they're very fiddly, but ...


5

Just to add to the previous answers... if you have a pattern beyond the Nyquist limit, you may experience aliasing — i.e. it may show as a lower frequency pattern in the image. This used to be very apparent on things like checked jackets on TV. Therefore, you do need a low pass anti-aliasing filter before sampling so that this artifact is not a problem.


5

I would put it through a series of situations: Low light/Noise Handling - take a shot in relative darkness to see how the camera handles noise and a slow shutter speed. High contrast - take a shot with a big difference in light and shade to test the dynamic range. Detail - take a shot of something with fine detail to test the resolution and sharpness. ...


5

I've read the Norman Koren tutorial on the subject a few times and he offers up a test chart as well as some links to others (some are dead, however). In a nutshell, however, you basically need: A lens test chart. The usual reference is the United States Air Force lens test chart, but there are variations on this and he suggests that it's inappropriate for ...


5

Make the photos you bought the lens for. For each feature of the lens that is important for you, make a photo that utilizes it. Only you know why it is important to you, so you can construct the best test photo. For example, I really hate having color aberration around tree branches in front of clear sky, so I'd test for that. Make sure the lens has an ...


5

If you have a point lightsource at a known distance and you know the focal distance (the distance to which the lens is focussed) then you can calculate the aperture based on the size of the circle of confusion (the round blob you get when a highlight is OOF). I don't know the formula off the top of my head but it could be rearranged from the depth of field ...


4

I use DxOMark to compare technical lens data. They use a standard test process to measure and compare the following lens parameters: Resolution Transmission Distortion Vignetting Chromatic aberration These data points are taken at different focal lengths (for zoom lenses), at different apertures and are tested on a variety of camera bodies. ...


4

Karel's sample shot has a strong greenish color cast because every "pixel" is processed without weighting, which therefor gives green twice the effect as red and blue. The result is an image processed from minimally amplified pixels, where as normally red and blue channels would be amplified by a factor greater than one to compensate for the greater number ...


3

I think your first stop should be at Imatest, which offers many different suites of tests widely used by large commercial & industrial customers. That said they also cater for the individual, check out in particular the Imatest Master. The downside is the purchase price (although there seems to be trial version available) and you may need extra test ...


3

Assuming a standard lens, standard camera, i.e. the setup can be modelled as a pin-hole camera. This doesn't work with tilt/shift, and maybe not with wide-angle lenses (if you want to know about those, we could work it out). In computer vision, often the intrinsic properties of cameras are calculated. Intrinsic because they refer to settings of the camera ...


2

To prove how bad things are :) you need to set an exposure which will give a dark output without under-exposing. Use something with fine-details or a texture. Noise is always most apparent in dark regions and its effect it to destroy fine-details. To see how good things are ;) do the same with a bright exposure, without over-exposing of course. Use a ...


2

You can probably calculate this by rearranging the DOF formula to solve for c, or circleOfConfusion, as @MattGrum stated. I haven't tried to rearrange a formula as complex as DOF for a while, so I hope my math is correct here: DOF = (2NcF^2s^2)/(f^4 - N^2c^2s^2) The terms of that equation are as so: DOF = depth of field N = f-number f = focal ...


2

The aperture f-number describes the amount of light that passes trough the lens, for a theoretical single element lens this is also the ratio between focal length and physical size of the entrance pupil - but no camera lens sold today is a single element lens. In 1874, John Henry Dallmeyer wrote that the only way to get the "intensity ratio" (that was ...


2

One suggestion from the link (http://www.guillermoluijk.com/tutorial/uniwb/index_en.htm) provided in my original answer: The steps would be: Shoot at some brilliant source of light for a couple of seconds, so that all three channels get blown in all pixels Use the resulting RAW file that will be in the memory of the camera to set custom ...


2

When I do such photos I alway use: a tripod to make sure the photo shows the same especially in the corners M-Mode with fix ISO-Settings to make sure exposure is same (be careful with fluctuating available light) Often but not alway I use flash and "kill" the available light to avoid light fluctuations. To analyses distortions I often use checkered ...


1

Traditionally, hoods were used to prevent lens flares and other light from getting into the camera. Nowadays, it's more about protection of the lens as no one cares about a slight contrast change in their photograph. Digital world... :sigh:


1

Take a look at a sample test on photozone.de. They have standardized test results available for distortion, vignetting & CA and MTF charts. (Although these might be generated by imatest.com test suite)


1

I looked at Bob Atkins' "Easy method", but it leaves you to work some astro data out. My version of his method provides all the astro how-to info and links, with step-by-step instructions, and should be significantly easier for novices to implement. ...



Only top voted, non community-wiki answers of a minimum length are eligible