Are Nikon Distortion Control Data firmware updates critical?

Question

Nikon has released the Distortion control data upgrade for D90 and D5000 (I am an owner of Nikon D90).

The Distortion Control Data firmware upgrade is available for Nikon D90 and D5000 cameras only. This is used to correct barrel and pincushion distortion during shooting and editing. This may be loaded into cameras that support distortion control.

Has anyone upgraded his/here camera by using this firmware? Is it a critical "bug"? Has somebody seen any difference before and after?

Other updates we can see here.

Related article: Where can I find firmware updates for Nikon and how do I install them

Asked by garik

Answer

No, I don't think it's a critical bug. This is an update of distortion data for Nikon lenses. As far as I know, the distortion correction is applied through the retouch menu, which I never use - I do any distortion corrections in Camera Raw.

The corrections applied are noticeable, if you see the before and after, but unless you see them on top of one another, or have an image of something like a brick wall, it's usually very hard to see distortion in most images, apart from very wide angle lenses.

Answered by MikeW

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What is the best way to take pictures for Panography style post-processing

Question

I have recently started to play with Panography, which is a style of stitching pictures together, however on my first couple of attempts, quite a few of the pictures that I took were distorted towards the middle of my scene; many of the objects weren't correctly aligned. Is there any way to remove any way to remove this distortion that before I take the picture?

Asked by Dylansq

Answer

It's hard to give a specific answer without knowing more about your post process workflow, but here are a few things you can try:

• Tripod to improve alignment of objects, or - even better - a tripod with a panoramic head.

• Shooting and a narrower field of view (shooting at 30mm instead of 17mm for example), this may help reduce lens distortion, though at the expense of having to take more images to cover the same area view.

• Tilt shift lens. Expensive! But will produce the best results possible.

However, I think your best bet is to try better software. Photoshop has a panoramic feature that handles distortion, color differences, and other abnormalities quite well. If you already have Photoshop, it's under File -> Automate -> Photomerge. There are other software packages that may also do a good or better job.

Answered by cadmium

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Are there any free or better alternatives to Fisheye-Hemi?

Question

I've been tempted to get a fisheye lens (The Nikon 10.5 DX specifically), and have seen the Fisheye-Hemi plugin for "normalizing" fisheye images.

Does anyone have experience of using the plugin or know of free or better alternatives?

Asked by Freed

Answer

As far as free alternatives you can try Fred's defisheye script for ImageMagick, or Fulla, which is a command line tool that comes with Hugin.

Fisheye-Hemi is superior to these, though, as instead of using a standard remapping to a rectilinear projection that softens the edges and requires an aggressive crop it uses a custom mapping algorithm that preserves much more of the original image and sharpness and still straightens out lines.

This blog post is interesting, the guy fed an image of a grid pattern through the Fisheye-Hemi plugin and then created a warp transform in Photoshop that approximately matches the deformation on the grid. Pretty clever.

Answered by Miguel

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Do the Lightroom lens correction tools make good lenses less important?

Question

Lightroom has Lens Correction tools such as Distortion, Vignetting, Chromatic Abberation, etc. depending on the brand and model of lens.

Due to this feature, it is less relevant what the distortion quality is of lenses because Lightroom can correct them?

I understand a perfect lens is always better, but since it can save a huge amount of money, maybe the expense is not worth it?

Asked by Michel Keijzers

Answer

The lens correction software may be able to counter lens distortion and chromatic aberration distortion. Also perhaps it can counter poor contrast to some degree. But a good lens has more to offer:

• Sharper image. The lens correction cannot restore image detail lost due to an unsharp lens.
• Aperture. Good quality lenses typically have a larger aperture. You cannot recreate the narrow depth of field from these larger apertures. And in low-light, you can only compensate by raising the iso on the camera, leading to more noise (which may be removed by software, but produces a softer image)
• Quality of the bokeh. A good quality lens produces a more pleasing bokeh than a cheap lens.
• Faster focus.
• Non rotating front element, making it possible to work with petal shaped lens hoods and polarizing filters
• It is nice to have something in the hand that feels solidly build

So you cannot let good software be a replacement for a good lens. IMHO, you should get the best possible lens within your budget that suits your needs.

Answered by Pete

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Nikon 50mm f/1.8 D has less distortion than Nikon 50mm f/1.8 G?

Question

Some of the Amazon reviews say that Nikon 50mm f/1.8 D has less distortion than Nikon 50mm f/1.8 G?

The D is about $80 cheaper, is smaller, lighter, has less distortion, and has manual aperture control.

D is an older version, and G has got more blades, so on what basis is do they say that distortion is lesser on the older lens?

Is this factor a deal breaker? Why would anyone purchase G then?

Asked by Anisha Kaul

Answer

Most lenses have some amount of distortion, it just may not be measurable or significant.

Thom Hogan says of the f/1.4G:

Linear distortion is low (though slightly higher than the f/1.4G) and barrel in nature. At under 0.5% it's not something I'd bother correcting unless I had software that did automatic correction based on EXIF data, in which case I'd just let that do its thing.

slrgear say this about the 50mm f/1.8

Distortion The 50mm ƒ/1.8 shows no distortion when mounted on the sub-frame D200. On the full-frame D3x, there is a negligible (+0.1%) amount of barrel distortion apparent in the corners.

Both lenses have 7 aperture blades, but that doesn't affect distortion. The f/1.8G blades are rounded, which will make the bokeh a bit more circular.

The more expensive f/1.8G has the following advantages over the f/1.8D

• sharper in the centre at wide apertures
• much sharper in the corners at wide apertures, most apparent with FX bodies
• AF-S focusing motor

Disadvantages

• more expensive
• lack of an aperture ring
• bigger and heavier
• 58mm filter thread (unusual for a Nikon lens - f/1.8D uses more common 52mm filters

So in summary, I don't think the distortion is a deal breaker. You would buy the f/1.8G if you needed an AF-S motor built in, or if sharpness was a big issue.

Answered by MikeW

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Nikon 1.8F D has less distortion than Nikon 1.8F G?

Question

Some of the Amazon reviews say that Nikon 1.8F D has less distortion than Nikon 1.8 G?

The D is about $80 cheaper, is smaller, lighter, has less distortion, and has manual aperture control.

D is an older version, and G has got more blades, so on what basis is do they say that distortion is lesser on the older lens?

Is this factor a deal breaker? Why would anyone purchase G then?

Asked by Anisha Kaul

Answer

Most lenses have some amount of distortion, it just may not be measurable or significant.

Thom Hogan says of the f/1.4G:

Linear distortion is low (though slightly higher than the f/1.4G) and barrel in nature. At under 0.5% it's not something I'd bother correcting unless I had software that did automatic correction based on EXIF data, in which case I'd just let that do its thing.

slrgear say this about the 50mm f/1.8

Distortion The 50mm ƒ/1.8 shows no distortion when mounted on the sub-frame D200. On the full-frame D3x, there is a negligible (+0.1%) amount of barrel distortion apparent in the corners.

Both lenses have 7 aperture blades, but that doesn't affect distortion. The f/1.8G blades are rounded, which will make the bokeh a bit more circular.

The more expensive f/1.8G has the following advantages over the f/1.8D

• sharper in the centre at wide apertures
• much sharper in the corners at wide apertures, most apparent with FX bodies
• AF-S focusing motor

Disadvantages

• more expensive
• lack of an aperture ring
• bigger and heavier
• 58mm filter thread (unusual for a Nikon lens - f/1.8D uses more common 52mm filters

So in summary, I don't think the distortion is a deal breaker. Youe would buy the f/1.8G if you needed an AF-S motor built in, or if sharpness was a big issue.

Answered by MikeW

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How do straight edges end up curved in photos?

Question

In the standard model for a lens straight lines in the subject of a photograph will always end up straight. However I have seen a variety of photographs in which straight lines end up being curved, e.g. the horizon tapers down at the edges, or a fence near the photo border is mildly curved.

What could cause straight edges to come out curved in a photograph? I have no idea what cameras were used in these cases, but I am certain they are standard consumer grade cameras (so they aren't fisheye type lenses such as equisolid angle lenses). Believe it or not I have to make computations based around objects in photographs and have no way of accounting for why straight things turn out curved in some photographs. From what I know about optics, this shouldn't happen, but it does, so I am missing something. What is it?

Can anyone give authoritative information about this?

Answer

You only get completely straight lines using a pinhole camera. As soon as you put a lens element in the path of the light, you get the fisheye-like distortion to some degree.

Modern lenses contain several lens elements which compensate for each other to give straight lines, but you usually get a slight distortion anyway. For really expensive lenses you have a very small distortion, but it's still there.

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What are Barrel and Pincushion distortion and how are they corrected?

Question

I have some questions regarding Barrel distortion and pincushion distortion. Since they are related I have put them in single post.

1. I am aware that barrel distortion occurs more in wide-angle lenses, wherein straight lines near edges of the frame curve outwards. Is it pincushion distortion when lines curve inward, and in what conditions (what types of lenses, etc.) does pincushion distortion occur?

2. I am aware that some new cameras (DSLRs, DSCs, SLDs) have in-camera corrections for these distortions, and also there are some tools to correct it in post processing (e.g., PTlens) but what is the exact procedure used in the correction process? Does the correction process work in Raw Bayer domain, or after some color conversion to YCbCr?

Any pointers (especially for question 2) would be useful, as I am trying to implement one post process for this type of correction.

Answer

1. Your interpretation of distortion is correct. For an example of a lens that exhibits barrel distortion at the wide angle and pin cushion distortion at the telephoto end, have a look at the Canon 18-135mm
2. Tools like PTLens and Hugin perform the corrections after the demosaicing of the Bayer data. I'm not sure why this would matter?

If you're interested in understanding how this correction is done, the equations are presented here.

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Is it technically possible to build a camera body to correct for lens defects?

Question

Most lenses tend to be expensive because the lens needs to be very complicated in order to correct for various optical effects (aberration, etc). Is it possible to build a sensor and processor combination which would fix defects produced by cheap lenses? I'm assuming the processor knows exactly the parameters of the len's defects.

Answer

Not only is it possible, but it's becoming commonplace. The micro-four-thirds system makes extensive use of it, and some compact cameras now do too. (I imagine that if they don't yet, most super-zooms will within a few years.) Digital Photography Review has a good article on this at http://www.dpreview.com/articles/distortion/ , and it's worth reading even if you don't like that site's reviews in general.

Correcting distortion and lateral chromatic aberration is an option in my Pentax K-7, but although it doesn't impact shot-to-shot time (unless you fill the buffer), it takes a few extra seconds per image.

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Can I configure the D7000 to perform lens distortion corrections on the embedded JPEG in the RAWs it saves?

Question

Lightroom eats the distortion present in the D7000's kit lens for lunch. However, it's time consuming to check which photos I like by performing this correction on all the photos in lightroom first. Ideally, I'd like to be able to view the images on the rear LCD screen with this kind of distortion already corrected.

Is that possible through some switch I'm missing?

Answer

No. It is not possible on the D7000.

Even though the D7000 can do it on JPEGs, it is questionable to do so on a DSLR. If you did that on the RAW preview, you would get a different image compositionally-speaking from the embedded thumbnail than the RAW.

This is a feature much better suited for SLDs and both Panasonic and Olympus have implemented it in the Micro Four-Third cameras. This is because the preview is digital and therefore is taken into account in the viewfinder. Otherwise you would not be able to frame correctly since distortion correction changes the framing of your images.

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