{"id":3230,"date":"2010-12-03T15:57:56","date_gmt":"2010-12-03T19:57:56","guid":{"rendered":"http:\/\/www.starkeith.net\/coredump\/?p=3230"},"modified":"2010-12-03T22:35:37","modified_gmt":"2010-12-04T02:35:37","slug":"not-all-f-stops-are-created-equal","status":"publish","type":"post","link":"https:\/\/www.starkeith.net\/coredump\/2010\/12\/03\/not-all-f-stops-are-created-equal\/","title":{"rendered":"Not all F-Stops are Created Equal"},"content":{"rendered":"

When I first started dabbling in photography, I did my usual reading-up on the technical aspects of things \u2013 shutter speeds<\/a>, f-stops<\/a>, circles of confusion<\/a>, depth of field<\/a>, etc. And for a long time, I thought I knew what I was doing.<\/p>\n

But recently I realized something that, in retrospect, I should have known all along \u2013 that not all f-stops are created equal<\/strong>. Or, to put it another way, f\/2.8 on my <\/em>camera might not be the same as f\/2.8 on your <\/em>camera.<\/p>\n

The key fact was that the f-stop is not an absolute size \u2013 it\u2019s a ratio<\/em>.<\/p>\n

This realization came about as I was trying to learn to do some creative depth of field related stuff with my Canon PowerShot S3 IS (as a follow-up to my previous experiments with depth of field<\/a>) and I just couldn\u2019t quite get that nice shallow depth of field I wanted. Then I was reading a new photography book I picked up recently called Understanding Exposure<\/a> and I suddenly realized what I had been missing.<\/p>\n

The basic principle is this \u2013 with point & shoot cameras (or any camera with a small sensor), the image being focused by the lens is being projected onto a very small square. In order to get the light to focus on this small square, your aperture (the size of the opening in the lens, which is what the f-number represents) has to be pretty small, otherwise the whole thing would be out of focus.<\/p>\n

Throw in some other limitations (like the smaller size of lenses overall in point & shoot cameras, and the smaller distances between the lens elements and the image sensor) and basically in these sorts of cameras you are always going to have a physically small aperture \u2013 even if the f-number suggests otherwise<\/em>. This is because the f-number is the ratio<\/em> between the physical size of the lens opening and the focal length of the lens itself.<\/p>\n

Because of this ratio nonsense, it means that you can have two cameras set to the same f-stop even though they have radically different physical sizes. The only thing that matters is the relative ratio between the lens opening and the focal length. Size is irrelevant.<\/p>\n

However, size most definitely IS<\/strong> relevant when it comes to determining depth of field (or more technically, determining the circle of confusion<\/a>). Because of their overall smaller sizes, point & shoot cameras come closer to being theoretically perfect pinhole cameras (which have theoretically infinite depth of field \u2013 or put another way, they have no blur because they focus everything perfectly). Larger cameras with larger sensors (and having both<\/em> of these things is very important) can generate a smaller depth of field, which is why photos from such cameras (e.g<\/em>., DSLRs) can achieve that amazing background blur that is often used to make interesting photos.<\/p>\n

\"cameraTo put this in concrete terms, when my camera is set to f\/2.8, it is focusing the image on a very small sensor (see the picture comparison of a point & shoot sized sensor to a DSLR sized sensor on the right). So even though the ratio of my camera\u2019s aperture gives us f\/2.8, the actual light rays coming in are focused very sharply in that very small space.<\/p>\n

Conversely, with a DSLR using a lens set to f\/2.8, the image is focused on a much larger sensor. Because of the larger size of the lens and the sensor, the light rays can be \u201cblurred\u201d out a bit more \u2013 the circle of confusion is bigger \u2013 and thus you get that nice shallow depth of field effect.<\/p>\n

It\u2019s this critical fact which explains why it\u2019s so hard to achieve this shallow depth of field effect on smaller sensor cameras (like point & shoot cameras \u2013 and that includes both compact cameras and even the physically larger \u201csuper-zoom\u201d cameras like mine).<\/p>\n

The next time you have your camera out, turn it around and look into the lens and see if you can see the aperture \u2013 the actual opening. If you can fiddle with the aperture controls while you\u2019re looking you can see it move, if that helps you identify it. If you have any sort of point & shoot camera, you\u2019ll see that it is actually very, very small \u2013 even if you\u2019ve set it to a \u201clarge\u201d aperture (small f-number).<\/p>\n

Of course, the other side of this coin is that point & shoot cameras have an amazingly deep depth of field – one that most DSLRs can only dream of. Still, in my experience at least it’s better to err on the shallower side, at least for the types of photos I like to take.<\/p>\n

People who are more knowledgeable about photography might be saying \u201cwell, duh\u201d at this point \u2013 but it really took me a long time before I understood all of this, and I have to imagine that there are lots of other casual, amateur photographers like me out there who maybe have been wondering the same thing. But now, hopefully, we all have a better understanding of how lens & sensor size affect depth of field, even though the f-stop number itself is the same.<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"

Explaining why that blurry background effect is harder to get on your point & shoot camera, even though you might have it set to the same f-stop as a DSLR.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"webmentions_disabled_pings":false,"webmentions_disabled":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"activitypub_content_warning":"","activitypub_content_visibility":"","activitypub_max_image_attachments":3,"activitypub_interaction_policy_quote":"anyone","activitypub_status":"","footnotes":"","jetpack_post_was_ever_published":false},"categories":[204],"tags":[247,92],"class_list":["post-3230","post","type-post","status-publish","format-standard","hentry","category-photography-pictures","tag-digital-camera","tag-photography","entry"],"jetpack_shortlink":"https:\/\/wp.me\/pimUj-Q6","jetpack-related-posts":[{"id":4500,"url":"https:\/\/www.starkeith.net\/coredump\/2014\/01\/23\/aperture-focal-length-sensor-size\/","url_meta":{"origin":3230,"position":0},"title":"Photography Experiments: Aperture, Focal Length, and Sensor Size","author":"Keith Survell","date":"January 23, 2014","format":false,"excerpt":"Just a quick photography experiment to demonstrate the effects that aperture, focal length, and sensor size can have on depth of field (i.e., how much you can blur the background of a photo.)","rel":"","context":"In "Photography"","block_context":{"text":"Photography","link":"https:\/\/www.starkeith.net\/coredump\/category\/pictures\/photography-pictures\/"},"img":{"alt_text":"snow on pine tree branch - f5.6","src":"https:\/\/i0.wp.com\/farm4.staticflickr.com\/3770\/12086166773_5f8cff5794_z.jpg?resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/farm4.staticflickr.com\/3770\/12086166773_5f8cff5794_z.jpg?resize=350%2C200 1x, https:\/\/i0.wp.com\/farm4.staticflickr.com\/3770\/12086166773_5f8cff5794_z.jpg?resize=525%2C300 1.5x"},"classes":[]},{"id":3749,"url":"https:\/\/www.starkeith.net\/coredump\/2012\/01\/21\/depth-of-field-experiments-parts-2-and-3\/","url_meta":{"origin":3230,"position":1},"title":"Depth of Field Experiments – Parts 2 and 3","author":"Keith Survell","date":"January 21, 2012","format":false,"excerpt":"More experiments into understanding and controlling depth of field (or the lack thereof) - this time, with my new camera and new lenses!","rel":"","context":"In "Photography"","block_context":{"text":"Photography","link":"https:\/\/www.starkeith.net\/coredump\/category\/pictures\/photography-pictures\/"},"img":{"alt_text":"depth of field experiment 2 (wine)","src":"https:\/\/i0.wp.com\/farm4.staticflickr.com\/3049\/3015399455_9f0d0615ff.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":1506,"url":"https:\/\/www.starkeith.net\/coredump\/2008\/11\/10\/depth-of-field-experiments\/","url_meta":{"origin":3230,"position":2},"title":"Depth of Field Experiments","author":"Keith Survell","date":"November 10, 2008","format":false,"excerpt":"Some experiments into understanding (and controlling) depth of field (or the lack thereof).","rel":"","context":"In "Pictures"","block_context":{"text":"Pictures","link":"https:\/\/www.starkeith.net\/coredump\/category\/pictures\/"},"img":{"alt_text":"wine line up","src":"https:\/\/i0.wp.com\/farm4.static.flickr.com\/3295\/3015399273_2ab12a3f9e.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":5879,"url":"https:\/\/www.starkeith.net\/coredump\/2022\/11\/15\/frosty-november-morning\/","url_meta":{"origin":3230,"position":3},"title":"Frosty November Morning","author":"Keith Survell","date":"November 15, 2022","format":false,"excerpt":"We had our first real solid frost last night - when I woke up it was 28\u00b0F (-2\u00b0C) out - and so of course I had to try and get some photos. https:\/\/flic.kr\/p\/2nZp3Hu However, I had just cleared all the leaves off the lawn this past weekend, and there are\u2026","rel":"","context":"In "Photography"","block_context":{"text":"Photography","link":"https:\/\/www.starkeith.net\/coredump\/category\/pictures\/photography-pictures\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":1056,"url":"https:\/\/www.starkeith.net\/coredump\/2008\/03\/03\/focus-focus\/","url_meta":{"origin":3230,"position":4},"title":"Focus… Focus!","author":"Keith Survell","date":"March 3, 2008","format":false,"excerpt":"I've been fiddling around with my camera again lately, and my feature-of-fiddling has been aperture, as it relates to the focus of the camera. Like a lot of people who get into photography (or so I assume), it's a little mind-bending at first with all the terms... focal length, depth\u2026","rel":"","context":"In "Pictures"","block_context":{"text":"Pictures","link":"https:\/\/www.starkeith.net\/coredump\/category\/pictures\/"},"img":{"alt_text":"lettuce closeup","src":"https:\/\/i0.wp.com\/farm3.static.flickr.com\/2236\/2303305594_0a3a224749.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":3156,"url":"https:\/\/www.starkeith.net\/coredump\/2010\/07\/31\/why-i-still-use-my-canon-powershot-s3-is-camera\/","url_meta":{"origin":3230,"position":5},"title":"Why I Still Use My Canon PowerShot S3 IS Camera","author":"Keith Survell","date":"July 31, 2010","format":false,"excerpt":"Why I still use my 2006 vintage Canon PowerShot S3 IS Camera, despite being a bit old.","rel":"","context":"In "My Opinion"","block_context":{"text":"My Opinion","link":"https:\/\/www.starkeith.net\/coredump\/category\/personal\/my-opinion\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.starkeith.net\/coredump\/wp-content\/uploads\/\/2010\/07\/Canon_Powershot_S3_IS-300x185.jpg?resize=350%2C200","width":350,"height":200},"classes":[]}],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/www.starkeith.net\/coredump\/wp-json\/wp\/v2\/posts\/3230","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.starkeith.net\/coredump\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.starkeith.net\/coredump\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.starkeith.net\/coredump\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.starkeith.net\/coredump\/wp-json\/wp\/v2\/comments?post=3230"}],"version-history":[{"count":0,"href":"https:\/\/www.starkeith.net\/coredump\/wp-json\/wp\/v2\/posts\/3230\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.starkeith.net\/coredump\/wp-json\/wp\/v2\/media?parent=3230"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.starkeith.net\/coredump\/wp-json\/wp\/v2\/categories?post=3230"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.starkeith.net\/coredump\/wp-json\/wp\/v2\/tags?post=3230"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}