Resizing photos in PHP with correct orientation/rotation and retaining EXIF data

▼ When I got my first iPhone back in 2008, I hacked together a quick script that let me post photos from my iPhone to my website. However, iPhone photos are now 3 MB or larger, which is a bit much. So in practice I would edit the photos on my computer before posting them. But that gets old, so time for some automation.

The first photo I uploaded directly from my iPhone 3G, showing part of the script

Actually resizing images is easy enough in PHP using the imagecopyresampled() function. However, using the provided example script the result was that a photo that I took with my iPhone showed up rotated.

The reason for that is that phone cameras store the camera's rotation in the EXIF data, and the PHP image manipulation functions strip away the EXIF data. One way to solve this is to read the EXIF data using exif_read_data() and then rotate the image accordingly using the imagerotate() function as explained here. However, that still leaves an image with no EXIF data.

A better way to do that is by copying all the EXIF data from the original image to the resized image. This requires a bit of work, but there is a good example transferIptcExif2File() function in the user contributed notes for the PHP iptcembed() function.

Searching for this using Google didn't give me any results, so hopefully the above will be helpful to others running into the same problem. And as you can see, it works:

Permalink - posted 2021-11-28

Test post preparing for HTTPS

▼ For some time now there's been a push to move the entire web from HTTP (no encryption) to HTTPS (with encryption).

I never felt it was necessary to encrypt static content. But the time has come to cave to peer pressure, and enjoy a few benefits such as the ability to post images to web forums.

However, I still feel very strongly about everything remaining accessible over HTTP. If you go HTTPS-only, you are now relying on a certificate authority (as well as your own ability to keep certificates up to date!), and you're cutting off some older systems and losing some performance. Also, having to change everything wholesale will be somewhat of a nightmare.

The trouble is: how do use HTTP images and links on an HTTP page and HTTPS images and links on the HTTPS version of the same page? With dynamically generated pages that's not too difficult: just let the script insert HTTP or HTTPS as required. Or, even easier: use relative links, that don't include the domain name.

Unfortunately, I have my content spread around a number of subdomains, and most of it is in static pages.

Turns out that you don't have to choose between:

http://www.iljitsch.com/2021/11-20-test-post.html (absolute URL)

and

/2021/11-20-test-post.html (relative URL)

but you can also use:

//www.iljitsch.com/2021/11-20-test-post.html

That's a protocol-relative URL. So you do specify the domain name, but not HTTP or HTTPS (or any other protocol). So if you use such a URL as a link on an HTTP page, the link will use HTTP. If you use it on an HTTPS page, the link will use HTTPS. So that's perfect for links within the site and images on static pages that may be served over either HTTP or HTTPS.

Paul Irish has a blog post that initially explained that it's a good idea to use protocol-relative URLs, but the current wisdom (added to that post) is they are better avoided, as there may be some cross site scripting possibilities. But as I don't use any cross site scripting on iljitsch.com that's not an issue here.

So I still need to go over the entire website to make sure protocol-relative URLs are used where I can't use regular relative URLs.

Apart from that, the main complication is my RSS feeds. Unless I'm misremembering, I started using absolute paths for my images because otherwise the images wouldn't show up properly on RSS aggregators. So I probably need to rewrite relative and protocol-relative URLs in my RSS feed script.

This is a test post to see how relative and protocol-relative images and links are handled in RSS. So don't be alarmed if links or images in this post don't work if you're viewing this post through an RSS aggregator.

Let me plug Esperanto and do the opposite for nuclear energy with this relative image (link):

Then again, fossil fuels aren't ideal either, using a protocol-relative image URL (link):

More later.

Permalink - posted 2021-11-20

Review: Peak Design Anchor Links to quick-release your camera strap

▼ I've had a few Nikon cameras, and those always come with a perfectly usable strap. The only issue is that putting the strap on a camera and getting the length just right is a rather involved process.

And sometimes I need a strap, but in other situations, it gets in the way. So I asked about straps that are easy to attach and detach in a forum, and one of the suggestions was for a Peak Design strap.

Peak Design as an entire system, with different kinds of straps that all use the same quick release mechanism. Their straps seem pretty good but a bit more than what I need for my non-pro cameras and matching lenses.

So I decided to get the Peak Design Anchor Links. (About $20/€20.)

This is a small set that contains:

1. Four anchors
2. Two anchor links
3. Two rings

If you're into watching Youtube photography channels, you've probably seen the little black discs with a red edge that hang off of the sides of a camera before. The anchors click into the anchor links, which are of course attached to the ends of a strap.

A Nikon strap with anchor links on the ends and the anchors in the middle:

The anchors are quite small, here compared to some coins: 20 South African rand cents, 1 US dollar cent, 1 euro cent and 10 Canadian dollar cents:

The anchor's cord loops attach quite nicely to a Panasonic DMC-TZ70 compact camera:

However, the cord won't go through the holes on most Nikon cameras. I used the included rings with this Z fc:

On the Nikon F65 on the left there are no issues attaching the anchors, and on the D7100 on the right I used the triangles that the Nikon strap normally loops through. Not very elegant, though:

Verdict:

Attaching to many Nikon cameras is not ideal, but being able to take off the camera strap in seconds is really great.

The system is rated for 90 kg. When you start to see the yellow core of the anchor cords, you know it's time to replace the anchors. The anchors definitely won't come out of the links by themselves: you have to push the anchor down and slide it up until it comes out of the anchor link. So this seems like a very secure system.

The anchors are plastic so they won't scratch your camera, but I believe the anchor links are aluminum, so you'll probably want to take off the strap when putting away the camera.

I like the fact that you get four anchors, so you can outfit two cameras with anchors. Also, the anchors themselves are pretty easy to attach/detach, so you can use them with even more cameras without much trouble.

The only thing that could make this better would be "slim anchors" option with thinner cords for lighter cameras.

Highly recommended.

Permalink - posted 2021-10-16

Mixing old and new Nikon lenses and cameras

▼ Seven years ago, I wrote Understanding old Nikon lenses: AI, AI-S, AF and AF-S. A few things have changed since then, so I thought it was time to do a follow-up that looks at how well different Nikon lens generations go with different Nikon camera generations.

The easy solution is of course to uses lenses and cameras of the same generation. All Nikon cameras introduced since about 2015 work with all Nikon lenses introduced since about 2000. But where's the fun in that?

First: what’s new since my previous article: AF-P lenses, E lenses and the new Z mount.

AF-P

For the past 20 years or so, Nikon’s autofocus lenses used ultrasonic "silent wave" motors in their AF-S lenses. AF-P lenses use pulse / stepper motors. Those can make small changes very quietly, so they're great for video. A big difference between AF-S and AF-P lenses is that the manual focus ring on AF-P lenses is not mechanically connected to the lens elements. Instead, the focus ring sends information back to the camera, which then uses the focus motor to change the focus.

This change means that the camera needs to know about AF-P lenses, or you won't be able to focus. Cameras introduced starting around 2013 support AF-P lenses. For some of these, a firmware update is required, and possibly there will be some reduced functionality.

E (electronic aperture) lenses

AF-P lenses also tend to be type E, indicating the lens has an electromagnetic aperture diaphragm actuator. (Not to be confused with "E series" manual focus lenses.) Support for E lenses goes back a few years further than AF-P lenses, to around 2008-2010, depending on the camera type.

Z mount

In 2018, Nikon introduced the Z line of mirrorless interchangeable lens cameras, and these cameras no longer have the F mount that Nikon's SLRs have used since 1959. Nikon has released a number of Z mount lenses, which are all AF-P as well as type E lenses. Of course these lenses don't work on older cameras, but F mount lenses will work on Z series cameras through the FTZ adapter. All the discussion below is about F mount lenses, for Z type cameras use of the FTZ is assumed.

The lens types

From left to right: pre-AI, AF-S type G, AI, AF type D, AI-s

So now we have an understanding of the following types of lenses:

• Pre-AI: manual focus
• AI or AI-s: manual focus
• AF: focus motor in the camera body
• AF-S, DX and FX, ultrasonic focus motor in the lens
• AF-P, DX and FX, stepper focus motor in the lens

All types of AF lenses also have a CPU in them which lets the lens tell the camera its properties. Let's see how they work on different cameras. I'll talk about the following specific cameras that I own, or more broad categories:

• Nikon FE, standing in for the AI type manual focus film cameras (around 1980)
• Nikon F65, as an example of a late lower end autofocus film cameras (around 2000)
• DX, the lower end crop sensor DSLRs (D3x00 + D5x00 and their predecessors)
• D7x00 and their predecessors mid-range DX camera with AI/AF lens support
• FX, the full frame high(er) end cameras
• Z DX: the Z50 and Z fc
• Z FX: the Z5, Z6 and Z7

So here we go.

Nikon FE and contemporaries

• Pre-AI: camera doesn't know aperture setting, so problematic metering
• AI or AI-s: perfect!
• AF: good!
• AF-S type G: no aperture ring, so fixed aperture and problematic metering
• AF-P: focussing impossible

Nikon F65 and similar

• Pre-AI: mounting will cause damage
• AI or AI-s: no CPU, so no or problematic metering (manual focus)
• "AF": perfect!
• AF-S, FX: perfect!
• AF-S, DX: typically black corners, some lenses may work to some degree
• AF-P: focussing impossible

DX DSLRs (lower/mid-range)

• Pre-AI, AI, AI-s: no CPU, no metering
• AF: manual focus
• AF-S: perfect!
• AF-P: depends on camera age

D7x00 and its predecessors

• Pre-AI: mounting will cause damage
• AI, AI-s: no CPU, enter lens data manually (manual focus) (no metering on D7500)
• AF-D: perfect!
• AF-S: perfect!
• AF-P: depends on camera age

FX DSLRs

• Pre-AI: mounting will cause damage
• AI, AI-s: no CPU, enter lens data manually (manual focus)
• AF-D: perfect!
• AF-S, FX: perfect!
• AF-S, DX: automatic cropping, but viewfinder shows black corners, some lenses may work in FX mode to some degree
• AF-P: depends on camera age

Z mount DX with FTZ

• Pre-AI, AI, AI-s: no CPU, so stop down metering, reduced focus aids
• AF: manual focus, reduced focus aids
• "AF-D": manual focus
• AF-S: good, somewhat hunting and noisy focus in video mode
• AF-P: perfect!

Z mount FX with FTZ

• Pre-AI, AI, AI-s: no CPU, so stop down metering, reduced focus aids
• AF: manual focus, reduced focus aids
• "AF-D": manual focus
• AF-S FX: good, somewhat hunting and noisy focus in video mode
• AF-S, DX: automatic cropping, also the viewfinder image, somewhat hunting and noisy focus in video mode
• AF-P FX: perfect!
• AF-P DX: automatic cropping, also the viewfinder image

As always, additional caveats may apply, be sure to check compatibility for your specific camera before you go out and get new lenses.

Conclusions

It looks like the D7100/D7200 as well as the not-too-old FX cameras are compatible with all F mount lenses. There is not a single lens type that works fully with the entire range of cameras, but the AF type D lenses come closest: they work on the old manual focus cameras, work with with autofocus on the mid/higher end DSLRs and still work fully as manual focus lenses on all other cameras.

An AF type D lens is still largely usable on cameras like the Z family, where you'll have to focus manually. But with the traditional "electronic rangefinder" focus aid available, where the autofocus system tells you if you've achieved focus, that's actually a bit easier than on an old manual focus camera such as the FE. However, manual focus lenses without a CPU for some reason don't get full focus aids on the Z cameras. You can still focus very precisely by zooming the viewfinder, but this is quite slow.

So there you have it. I'm sure the next few years the second hand F mount lens market is going to quite interesting, as more and more Nikon users migrate to a Z camera or a non-Nikon mirrorless camera.

Update:

In the original version of this article, I mistakenly said AF lenses that are not AF-D lenses don't have a CPU. That's incorrect. On DSLRs AF and AF-D lenses work the same, but for some reason on a Z camera (through the FTZ) the AF-D lenses have full focus aids but AF lenses have reduced focus aids. However, AF lenses are still more functional than non-CPU manual focus lenses because on AF lenses, the camera can control the aperture.

On non-CPU lenses, the camera doesn't know the aperture so it's difficult to use apertures smaller than about f/5.6 or f/8 because focussing gets more difficult at smaller apertures, so you may have to use stop down metering.

Permalink - posted 2021-10-09