Thursday, March 7, 2024

Full Frame, APS-C, Micro Four Thirds, what does this all mean?

What is full frame and why is it a reference?

source: https://petapixel.com/color-photography/

In a nutshell - Full-frame was a popular film format, 36x24mm in size. That format carried through to today's professional digital cameras. Lens focal-length equivalence is often used because the same lens will give different compositions on different cameras. Discussion among photographers involving lenses would bring up full-frame equivalent focal lengths. This way, photographers using any format could follow along.

Kodak introduced "135" film in 1934 as a standard film cartridge. This film records images at 36mm x 24mm. By the 1960s, it was the popular standard. This popularity continued till the advent of digital photography. It left us with the common idea of the "professional" format - Full Frame - using these dimensions. The next major competitor is APS-C - a similar rectangle at 2/3rds the side length. Micro Four Thirds is another format even smaller than APS-C. By the time the digital age was upon us, 35mm film/cameras/lenses had dominated the industry for decades. Cost and technical difficulty propelled smaller digital sensors into lower-tier consumer markets, with the expensive "Full Frame" sensors directed to professional or higher-end consumers.

A given lens will create an image when focusing on a medium. The image can be recorded on photographic film or a digital sensor. If you're curious, you can hold a lens near a window, and hold blank paper behind it. Move the paper close to the lens until the image is in focus. You should see an inverted circular image of what's outside the window.

Holding my Nikon 50mm and trying to focus it on this pad while taking the picture proved quite clumsy.

A full-frame camera would render a picture as if drawing a 36mm x 24mm rectangle in that image. An APS-C sensor is about 24x16, and would be that smaller rectangle. A M43 sensor would be a 17x13 rectangle in that image.

FOV Equivalence:

Right away the idea of smaller sensors being crops of the full-frame image should come to mind. It's a tighter field of view - so how can you get a similar picture? The main idea of equivalence should be about framing your shot. 

Let's assume that you liked 50mm lenses on full-frame cameras. If you picked up a micro four-thirds camera, what lens would give you a similar feel? Well because of the smaller sensor, you will need a wider lens. 25mm is quite close. If you were looking for a lens on APS-C cameras, you'd need 35mm.

This is where the idea of crop-factor comes into play. It is the ratio of the sensor's diagonal, comparing the full-frame sensor to the cropped sensor of APS*/M43 and other sensors.

APS-C has a crop-factor of 1.5 (in general - Canon does 1.6). Micro four-thirds has a crop factor of 2. These numbers can be used to quickly figure out equivalent focal lengths on their respective systems.

Most smartphone cameras have a crop-factor of 5 or 6.


Depth Of Field Equivalence:

When your camera is focused on a point, some objects in front of and behind that point are also in focus. This area of sharpness is the "depth of field". 

If I composed a shot on the full-frame A7II, then with the same lens I'd need to recompose on the smaller sensor Panasonic G9. I'd have to step back because the lens has a narrower field of view on that smaller sensor. If you step back, you increase the depth of field.

If instead I switch to a wide lens to compose the image in the same place? Wider lens, increased depth of field. The only way to frame it and get the blur right would be to use a wider lens and faster aperture.

If I wanted to blur the background of an image, and I shot 50mm F2.8 on the full-frame camera, I'd need to shoot 25mm F1.4 on the Micro four-thirds for the same shot. If I shoot 50mm F1.4 on the full frame, I wouldn't be able to copy the depth of field at that composition, because I'd require a 25mm F0.7 lens for micro four-thirds.

This will matter more to photographers using fast zooms, for which there are few equivalent options in crop sensor formats. A 2.8 zoom can still give great subject isolation and background blur on a full-frame camera. The equivalent would be an F2.0 zoom on APS-C or an F1.4 zoom on micro four-thirds. Lenses with those f-stops don't really exist (OK.. Sigma's F1.8 zoom and Panasonic's F1.7!) but some primes can deliver enough blur - or just shoot differently. Nobody says you must take every type of shot, with every camera.


Depth of field equivalence is usually not as important as some make it appear:

When taking pictures it's helpful to know the field of view. Are you shooting wide, normal, or telephoto. Are you trying to compress the image and pick your backgrounds or capture as much of the sky as possible?

I switch between full-frame and micro four-thirds, and rarely think about equivalence for depth of field. Macro excluded - that's always a special case here 😛.

For group photos taken indoors, I will likely need a wide field of view. I may use 14mm for micro four-thirds. I might use 28mm on my full-frame.

I'll probably shoot both kit zooms wide open at F4, and not care about depth of field, because the kit lenses are slow enough not to worry.

I love the shallow depth of field I can get with the A7II and a 50mm F1.4, but I'm also satisfied with what I can get (at least most of the time) with my micro four-thirds Panasonic G9 and some manual glass. I really love to melt messy backgrounds, and some speed-boosted primes are enough to do that.


Relatively cheap speed...

Canon 55mm F1.2 S.S.C. FD remounted to EF on Metabones focal reducer, 39mm F0.86.

Nikon 35mm F1.4 AI-s, adapted to Canon EF, on Pixco focal reducer, 25mm F1.0.



FOV Equivalence Table:


FFAPS-CM43
sensor width3623.6017.30
sensor height2415.7013.00
x/FF1.000.430.26


Full FrameAPS-CM43
Focal LengthFOV horizontalFOV verticalFOV horizontalFOV verticalFOV horizontalFOV vertical
12112.6290.0089.0466.3871.5756.89
14104.2581.2080.2558.5663.4249.81
1696.7373.7472.8252.2756.7944.22
2083.9761.9361.0842.8646.7836.01
2473.7453.1352.3636.2239.6430.31
3554.4337.8537.2625.2827.7621.04
4543.6029.8629.3919.7921.7616.44
5039.6026.9926.5617.8519.6314.81
8523.9116.0715.8110.5511.628.75
13515.1910.169.996.667.335.51
20010.296.876.754.504.953.72
3006.874.584.503.003.302.48
4005.153.443.382.252.481.86
6003.442.292.251.501.651.24
8002.581.721.691.121.240.93
10002.061.381.350.900.990.74
12501.651.101.080.720.790.60


How to calculate the Field of view? Trigonometry!
e.g.










Tuesday, September 12, 2023

Analyzing my lens choices

So, I took a trip...

I don't take long trips away often. So when I do, I have to seize the opportunity. I was heading to Canada on a cruise. My travel budget (both $$ and lbs) lent a generous portion of itself to photography. The then, is "What lens to take?". 



And I took some lenses...

I have a decent collection of micro four-thirds glass, and a fair number of adapted lenses too. My breakdown for what I took:
  • Panasonic 12-60mm F3.5-5.6: Solid general zoom lens. Great in bright light. Quite wide for a kit zoom.
  • Olympus 75-300mm F4.8-6.7: My long zoom. Possibility of birds, whales, and other wildlife - this definitely gets in my bag. The lens also provides certain background compression opportunities. e.g. Taking a picture of someone with a far-off object in the background, taking up most of the picture.
  • Sigma 16mm F1.4: I've been loving this lens a lot lately. It's a 32mm equivalent, which is sort of a "wide-normal" focal length. It's bright - so it's great for indoors.
  • Samyang 50mm F1.4 + Metabones Focal Reducer: As a 35mm F1.0 lens, this is still my favorite portrait combo on M43. I wasn't expecting to use this much - but just in case.
  • 7Artisians 7.5mm F2.8 Fisheye: Another manual lens. this fisheye gave me some of the best pictures of the last holiday. When you cannot get a wide enough view, this works wonders.
  • Panasonic 20mm F1.7: Both my wife and daughter carried their Olympus E-M10 I and III cameras with version I and II of this lens. It's a nice pancake with excellent sharpness.

Analyze photos with exiftool and WSL:

I used exiftool to check image information. Windows Subsystem for Linux is one of the few things that keeps me with a Windows box still. 

Install exiftool (WSL/debian/ubuntu):
sudo apt install libimage-exiftool-perl

Usage:
exiftool yourimage

I wanted output I could parse easier, so
exiftool -json yourimage

e.g.

So... many... fields!!!
I really just want the lens and focal length fields.

$ exiftool -json PRJC5662.JPG  | jq -c "{Lens:.[].LensID,FL:.[].FocalLength}"
{"Lens":"LUMIX G VARIO 12-60mm F3.5-5.6","FL":"15.0 mm"}


Next step - dump just the specifics on each file - lens and focal length.


#!/bin/bash
origdir="/mnt/d/library/htdocs/Pics/2023" #Parent folder of image folders
#iterate across all subfolders needed
for folder in "08/24" "08/25" "08/26" "08/27" "08/28" "08/29" "08/30" "08/31" "09/01" "09/02"; do
  cd $origdir
  cd $folder
  alljpegs=`find . | grep -i "jpg$"`
  for afile in $alljpegs; do
    bfile=`basename $afile`
    ffile="${origdir}/${folder}/${bfile}"
    exifdt=`exiftool -json $afile  | jq -c "{File:\"$ffile\",Lens:.[].LensID,FL:.[].FocalLength}"`
    echo "$exifdt"
  done
done | tee ./lensinfo.json

This produces leninfo.txt, where I can just grep the information, and pipe the output to wc to count matching lines.

The output looks like this:
{"File":"/mnt/d/library/htdocs/Pics/2023/08/24/08/24/LLC10011.JPG","Lens":"Lumix G 20mm F1.7 Asph.","FL":"20.0 mm"}
{"File":"/mnt/d/library/htdocs/Pics/2023/08/24/08/24/PRJC4306.JPG","Lens":"SIGMA 16mm F1.4 DC DN | C 017","FL":"16.0 mm"}
{"File":"/mnt/d/library/htdocs/Pics/2023/08/24/08/24/PRJC4308.JPG","Lens":null,"FL":"0.0 mm"}

For example - If I want to know how many pictures were taken with the Sigma 16mm lens:
$ ∙ cat lensinfo.txt  | grep "SIGMA 16" | wc -l
311


Manual lenses are the reduced 50mm F1.4 (35mm F1.0) and fisheye.
I need to visually determine these.

A quick loop is all that's needed - I copied photos with manual glass to a temp folder, and just dragged photos that looked like non-fisheye to another.

mf_fh="${HOME}/scripts/photag/mf/fh/"
while read -r line; do
  if [[ "$line" == *"Lens\":null"* ]]; then
    fname=`echo "$line" | jq -r ".File"`
    cp "$fname" "$mf_fh" &&echo "copied $line"
  fi;
done <<< `cat ./lensinfo.json`


That dropped maybe 200 files into the fisheye folder. I barely used my 50mm so should be quick.



Out of ~200 photos, 15 were shot with the 50mm and 179 with the fisheye.

Lens use tally:
LensCount
Sigma 16mm311
50mm F1.4 + MB15
75-300mm284
12-60mm384
7Artisians FE179
Super Wife952
Awesome Kid120



But.... This was just an initial check - how many of these are keepers? Some may not be great. Burst shooting was used for a few. These pics are informal for my family, so I'm being less stringent on what I remove.  What does the final tally look like?

LensCountKeeper Rate
Sigma 16mm22572.35%
50mm F1.4 + MB1066.67%
75-300mm26593.31%
12-60mm30178.39%
7Artisians FE11664.80%
Super Wife75679.41%
Awesome Kid7965.83%


How often I used a particular lens:




Shooting patterns:

Well right off the bat I can see that if there's any lens I leave behind on a scenic trip, it's the 50mm F1.4 + MB reducer. It's a great lens. A favorite. It just obliterates the background. If the objective of the photo is to capture the subject (people) with the surroundings, it's not the right lens for the job. Nice render though 😁

I love the way this lens renders bokeh. I can stop down for the background, but at that point, I'll just use the regular zoom.


Of my own pictures, the 7Artisians Fisheye was the next least used (still significantly used over the 50 though!) - but it also gave some of the most impactful pictures! It will capture the sweeping curves of the cruise ship's structures, or just deliver a perspective otherwise impossible to capture. The image can be fully defished to give a wide rectilinear result, or slightly to keep a bit of that distortion.

A spiraling staircase led from the 3rd floor to the 5th. Keep subjects near the center of the frame and step back. This keeps them from getting too distorted. 


the fisheye also fares well in the ship's main dining room.




Sometimes you just want pictures with tall buildings, statues, and monuments - and it feels impossible with most lenses. Without being able to step back a lot, the 7Artisians Fisheye was able to capture the top of the lighthouse.


When you want all the sky...



Sometimes you just want more width and a consistent hyperfocal distance that puts everything in focus.


Being close to the ship wasn't a problem. I did slightly defish the image.

Photography on a ship can be tough with unforgiving lighting conditions. Lights come at bad angles casting shadows on faces. Lights from different areas have different colors making white balance tough. A fisheye captures so much, that it's even tougher to balance exposure and color.




Next up, is the 12-60mm lens. I went into this not realizing how much I'd use it. I barely used this lens when on the ship. Out in the sun during the day, however, it was really effective.

Arcadia National Park, Jordon Pond


Cape Elizabeth, Portland Head Light


Nova Scotia,Peggy's Cove Lighthouse


Strength of a zoom, is in composition and framing. I took this from a bridge in Concord. I saw the boathouse through a gap in the trees. The kayakers were a welcome addition.

The 12-60mm isn't a macro lens, but it can give a respectable close focus in a pinch when desired. With an achromatic close-up filter, it does have fair macro capability.




The Olympus 75-300mm is a long zoom. It's good for wildlife, far-off structures, and even for portraits where you want to have something in the distance fill the background.




I didn't see any whales, puffins, or other wildlife. Birds seem to like flying by cruise ships though. I guess they use the rising warm air as a pick-me-up.


We passed the Cape Elizabeth lighthouse while pulling out of Portland. At 156mm (312mm effective in full-frame terms) It fills the available space in the background. 


The Sigma 16mm is fast becoming a favorite of mine. The F1.4 aperture is nice and bright for indoors and at night. It's somewhat wide, giving a decent depth of field. Sharp, flare-resistant etc... It's a good lens. A little big though, especially compared to the competition - a 15mm F1.4 Panasonic and 17mm F1.8 OM. It is cheaper though, and doesn't seem to sacrifice image quality. 

Night on a cruise ship is generally quite dark. It certainly wasn't this bright. Faces are perpetually ill-lit, with multiple light colors to make post-processing a pain.


The arcade is one of the darker areas on the ship. A bright F1.4 lens really shines here - especially if it's wide enough to capture more.



It's a fast lens - but that doesn't mean it's useless in bright light. You can stop down - or just let it rip and enjoy a bit of background blur.


The 16mm F1.4 gives a 32mm effective focal length on Micro Four thirds. It's a nice wide-normal type field of view, making it really comfortable to use indoors.

It was a cruise - it won't be complete without a food pic 😁. Last night of the cruise - Lamb and vegetables.





Final thoughts...

If I had to use one lens, it would easily be the Sigma 16mm F1.4. It doesn't have to specifically be this lens - the 15mm Panasonic and 17mm Olympus are also great options for normal-wide type primes. The ability to shoot in dark areas is great. I didn't bother to take it outside, because I had the 12-60mm zoom - but it would fare well outside too, just stopped down. It wouldn't have the versatility of the 12-60mm of course.

Why doesn't this apply to the 50mm? Well, 50mm on the micro four-thirds platform is an effective 100mm. It's too narrow a field of view, making it rather restrictive. The reducer makes it 35mm - but that's still too narrow.

The next lens in my arsenal I wouldn't go without is the fisheye. I used the zooms far more than this lens, but I was really pleased with the standout fisheye results.

Other than the 50mm F1.4 (35mm F1) that I could definitely do without, what else would I probably drop? It might be the 75-300mm. I got some great shots with it, and there's always the possibility of wildlife where I just need that range - but nothing really stood out this time. Perhaps a better idea would be a superzoom lens - Olympus has a 12-200mm superzoom (though costly!). Tamron has a 14-150mm that has decent sharpness (and it's cheap too).


How do you carry what you need comfortably? Get a decent bag. A small sling is fine for light loads. Get a proper backpack when it starts getting heavy.

5 Lenses, the Panasonic G9 Camera, a 360 cam, tripod, spare cards, adapters, wipes, my laptop, tablet, chargers, snacks, passports etc. all fit in this bag. A Tarion Pro backpack. If you want to carry 2 cameras, or even 2 systems and a laptop, this will do this very nicely. On the ship I used my Domke F-802 "reporter's satchel" - seen rolled up and being carried by the Tarion in the rear straps.