Recent Posts | Submit an Article | Back to Basics | Reader Photos | Forum | Subscribe
Home Studio | Tutorials | Readers Projects
Removing The Mystery From The Heart Shaped Bokeh Thing
Fri, 2008-08-22 22:45 — udijw
One of the most popular posts here at DIYP is the Create Your Own Bokeh post - this is the one that teaches you how to make nice shapes in the blurred area of your image - AKA Bokeh.
It is a nice thing because, usually, those hotspots are just taking away from your subject attention, and if you apply this technique, those annoying hotspots can become part of your artistic say.
Creating your own bokeh shapes is easy and fun, however there are a few repeating questions that I frequently get by email and comments. This is why I was really happy to learn that manimal magic has done some great thinking and have solutions for all questions. Some of manimal magic's wisdom was found in the comments of the original post, and some was taken (along with the images for this article) from his (really awesome) Flickr stream. I am going to format this as a Q&A thing, cuz it really feels like he's answered all the hard questions.
How Small Should I Make The Shaped Hole?
Well, that really depends on the aperture your lens have and on the focal length you are shooting with. The calculations below are based on the assumption that the black card is placed directly on the outer glass. In real life there is a bit more distance created by a filter, so the size needs to be a bit smaller
Because we are creating a new aperture, it must be smaller than the one inside our lens. This of course is how a lens works - it is one big aperture with a
smaller one inside. All we have done is supplement the old aperture :)
If we take a "large" aperture, say a value of f/2 - this just expresses
the ratio of the focal length to the diameter of the aperture.
In a prime lens of 50mm with an aperture setting of f/2 the aperture
will be 25mm, so your cutout shape must be less than 25mm in diameter
to get the effect.
A prime lens of 100mm at f/2 will have an aperture diameter of 50mm,
which is why they are so big and heavy and expensive, and your pre-cut
shape can be up to 5cm in diameter.
How do you know how big of a hole to make and what settings to use on any lens?
The shape you make must be smaller than the aperture in your lens.
Take the focal length that you wish to use (e.g. 100mm)
Divide this by the aperture value that is smallest on your lens (e.g. f/2)
In this case the diameter of the lens aperture is 50mm.
If you make your shape smaller than 50mm across the effect should work as shown above.
50mm f/2 - shape must be less than 25mm across
75mm f/2 - must be under 37.5mm across
100mm f/2 - must be under 50mm
50mm f/2.8 - must be under 17.5mm
50mm f/3.5 - must be under 14.2mm
Can I use this cool trick with my point and shoot?
Well, that depends on how small you can make your punctured hole. The focal length of a regular point and shoot is about 7 millimeters on the wide side and about 12 millimeters on the zoom side. (I'm talking real focal length and not crop factor equivalent).
That means that your hole will have to be about 2.5 millimeters at 2.8 wide. Not that trivial, but possible.
How do I make the hole in the dead center of the lens?
One of the key points to utilizing the entire "new" aperture is to place it on the dead center of the black card or cap of the lens. It's real easy if you make two lines to form an "X" on the card board. See the picture to the left.
Once you have the cross to mark the center, simply place your hole on the middle of the "x". As my good friend Indy use to say "X marks the spot".
If you like this art, you can find a great collection of images on the DIYP Flickr group.
Related Links:
- Shaped Bokeh on Flickr
Great Bokeh Lenses:
Want to make sure you get more great articles? Register to the RSS feed or the newsletter.
Bookmark this post with:
Comments
Ok, i was able to build my
Ok, i was able to build my own bokeh...i made it on a triangular shape.
My only doubt is how should i place the lights to achieve the kind of effect that you got on those photos...i've only been able to make it with street lights set far far away from me.
Bokeh and Distance
Hi Rafael,
To make the Bokeh magic you need to make sure that the bright spots of light are A - bright and B - off focus.
Street lamps is indeed one way of doing it. If you'll look at the pool, you'll see that most bokeh pictures are made with a really (really) close object and some relatively distant lights - street lamps, candles, stars...
new! a dedicated flickr group for it:
Shaped Bokeh
http://www.flickr.com/groups/shaped_bokeh/
WOW Fabio
Looks like you are on with a great start. I added the group into the article.
Cool group!
In the photo above the doll is at the lenses minimum focus distance (about a foot away for this lens) and the lights about 3 feet away.
In the question mark photo the lights are just taped to some black card about one foot behind the model.
Great post!
This is a very interesting technique. I have not seen this before.
I managed to get the effect
I managed to get the effect without the black card by misfocusing on some street lamps and zooming in a lot.
I guess I'd like to know what I'm supposed to see in the viewfinder to get the effect? Black screen with small hole or black screen with large hole? Because, so far nothing has worked with the black card and the shape...
re. black card
If you look through the viewfinder and you see the black card with a hole in it, the effect has not worked.
Look at the photos above - they look like regular pictures, there is no hole in the middle.
These photos have not been cropped - when your hole is the right size you will see a picture like the one above, and you will not see the black card.
Let's take your example.
Point the camera at the lights and defocus so that you see the lights turn from points of light into circles of confusion.
Check the aperture in your camera. This should be as big as possible, and this means the number should be as small as possible, eg. f/2 or f/3.5, but not f/8 or f/14.
If you do this, then simply adding the black card with a small enough hole in it will get you a picture like the one above.
Here is an example of what you see at the moment.
This is not good - either the hole was made too large, or the aperture inside the lens is too small.
The shape you put in front MUST BE SMALLER than your aperture.
If this STILL does not work, please post here what type of lens you have. If you include what focal length it is, eg. 100mm or 70mm, and post it's biggest aperture size, eg. f/2 or f/3.5, then we can calculate for you what size of hole you must use to get the effect above.
Great tips
Thanks for helping to clear this out. The idea about defocusing first is great.
It still doesn't seem to
It still doesn't seem to work. Sigh...
I have an 18 - 200mm, f/3.5 - 6.3 lens.
hmmm
Well, I am guessing your lens only does like f/5.6 as you zoom out a bit.
We want to keep the aperture large, and we want to be able to create some background blur.
If we tried 18mm, even at f/3.5 this makes an aperture diameter of around 5mm - your hole would need to be smaller, and that's pretty small.
So lets try something larger - 70mm and f/5.6. Remember that f/5.6 just means focal length (f) divided by 5.6, so this time the aperture is 12.5mm across, and your shape can be one cm or so.
Try this - make sure the black card completely covers your lens and male sure the hole is in the middle.
Put the camera on aperture priority mode.
Set the aperture to f/5.6.
Set the lens to between 70mm and 100mm.
The shape you cut out must be smaller than 1cm across, try no bigger than 8mm.
If you do this you will see the effect - if not keep zooming.
There must be something in the background to blur also, like streetlights in the distance.
I hope this works :D
Great fun
I gave it a go with my totally inappropriate 70-300mm f4 lens and managed to get it working. Nice trick. More details here.
Works better now! I got the
Works better now! I got the circles of light to look like my shape and there isn't the shape in the viewfinder. Now I just need to try and get it to fit the whole frame.
Thanks for your help!
I've tried a few times, used
I've tried a few times, used f2.8, and the shape is less than 5mm, but I still can't do it :(
I have an 17-50mm f2.8 -22 lens
thanks!
17-50
I'm not sure if your lens does f/2.8 throughout the zoom range, so I will work it out for something that you will be able to access with any lens, like f/5.6.
f/5.6 is just the focal length divided by that number, so for 17mm it is 17/5.6, around 3mm - way too small.
But f/5.6 at 50mm is 50/5.6, around 8 or 9mm across.
So if you set your lens to f/5.6 (or lower, go f/2.8 if you can) and also to 50mm, your shapes should work.
If you set your lens to 17mm and f/2.8 for example, 17/2.8 is close to the 5mm your shapes are now, and this might be why it doesn't work.
If you zoom in to 50mm and it STILL doesn't work, try a slightly smaller hole, but hopefully your current 5mm hole will work at f/5.6 or less at 50mm.
;]
Camera Aperture
Hi I have used this technique in the early 80s and shot a calendar using a middle format camera Mamiya RB67 Pro with 127 mm lens.
I would like add that we donot use the camera aperture and we keep the camera aperture at its maximum opening.
We are adding an external aperture by way of a shape in black card board/plastic/metalic sheet in front of the lens as a filter.
The size of the shape being cut in the center as shown in the diagram should be like F11 plus.
The bigger the distance between the subject and background that have specular / hotspots.
focusing
what a great idea u have. How about the focusing?...which one is the best, manual focus or automatic focus? please tell me more about the focusing technique to get a great picture with custom bokeh.
focusing
Well, most of your shapes will have a definite shape and orientation to them.
You want your hearts with the pointy bit down, that kinda thing :P
It's easiest to adjust the focus manually, and when you get it right then adjust your shape to make it the way you want it.
In fact, if you can focus and then add the card afterwards it is probably even better - but either way, autofocus could end up messing your shot in this case by moving your shapes when you don't want it.
Go manual >:-]
Post new comment