Frustrated - New Extension Tubes and Distortion

[Ed Bray]

After reading through this thread and your answers to questions asked by other members I can't help but think that you are trying to run before you can walk. To assume that a limited Depth of Field (DoF is the amount of perceived sharpness either side of the actual point of focus) is a form of lens distortion just further emphasises this feeling. DoF is a result of image magnification and can be effected by focal length, lens to subject distance and the aperture selected.

After reading various reviews of the extension tubes you have purchased it would appear that they are not the most reliable of items with owners having had issues with the plastic build, frequent issues with the contacts in particular especially when all three tubes are mounted together. There is an old adage of buy well, buy once and this would appear to be one of those times.

Can I ask why you felt you needed the extension tubes when you already have a lens that focusses to life size, have you outgrown it and are looking to improve upon your results?

From reading your last post it seems that you have little idea of photography at all, your third sentance in post #15 states you have absolutely no idea of the controls of which you are required to understand in order to operate the camera to acheive the results you want. Either that or you are a troll and this is just a wind-up.

My suggestion would be to read and understand the basic principles of camera operation and how the changing of the various controls allow you to alter the final result. If you can find a mentor locally who can guide you in the right direction that would be of benefit too.

Fortunately, in this digital world it will cost you little but time to experiment and learn the basics, in years gone by when using film, this was an expensive and time consuming business.

 

[Judobreaker]

Aperture: Lens opening.
Controls Depth of Field (DOF, the area in which objects appear sharp and in focus).
The F-number is the aperture setting. For example f/2 is a larger opening than f/8.
A larger opening lets in more light so this will also enable you to choose a higher shutter speed.

Simply put: More DOF = Less light.


Shutter speed: The time your shutter is opened.
Shutter speeds are displayed in parts of a second. For example 1/250 is faster than 1/10.
A slower shutter speed will make your sensor catch more light, thus making the photo lighter.
Slow shutter speeds will also introduce motion blur if the camera or subject moves.


ISO: The sensitivity of your sensor.
Controls how sensitive the sensor is to light.
When you increase the ISO you will need less light to get a good photo.
Increasing your ISO will also increase image noise.

Simply put: Higher sensitivity = More noise.


Exposure: Aperture + Shutter speed + ISO
This is basically all of the above combined. The optimal exposure is exactly what you need to get a well lit photo.
Basically this is a constant. If you increase one factor you have to compensate it with another factor.
For example, if you increase your DOF (by closing down the aperture) you will lose light and therefore have to decrease shutter speed or increase ISO.

 

[Ed Bray]

F-stop: DOF + Shutter speed + ISO
This is basically all of the above combined. The optimal F-stop is exactly what you need to get a well lit photo.
Basically this is a constant. If you increase one factor you have to compensate it with another factor.
For example, if you increase your DOF (by closing down the aperture) you will lose light and therefore have to decrease shutter speed or increase ISO.

Not sure where you are coming from here, an 'f stop' is simply the size of the aperture in the lens divided by the focal length (50mm lens with a 25mm hole = f2), the name 'stop' comes from the early days of photography when a board with a hole in it of a given size was placed in the light path of a lens to control the exposure. The photographer carried boards 'stops' with various sized holes and inserted the one required.

The optimal f stop has nothing at all to do with getting a correct exposure unless the other variables are adjusted to acheive the required 'Exposure Value.' You can have an incorrect exposure with your optimum aperture and you can have a correct exposure with an aperture other than your 'optimal'

 

[Judobreaker]

Oh lol, I haven't been too sure but I always thought people were using it like that.
Sometimes people use the words f-number and f-stop in a single story which has probably gotten me confused sometime.
Oh well... I'll just change that to 'Exposure" and it'll be correct.

 

[Helen B]

Not sure where you are coming from here, an 'f stop' is simply the size of the aperture in the lens divided by the focal length (50mm lens with a 25mm hole = f2)

That might be just a little confusing, mightn't it? The f-number is the focal length divided by the diameter of the aperture (actually the diameter of the entrance pupil); and because f-number and the less well defined f-stop are often used interchangeably it could be confusing, especially to a beginner, to call the f-stop the 'size of the aperture divided by the focal length'.

 

[Overread]

I would strongly recommend two things

1) read - reread and read it again - the manual that came with the camera (if you don't have it it should be on the Canon website for download). This tells you what is what in your viewfinder; how to adjust settings and short overviews of the features and their uses.

2) Read the book "Understanding Expoosure by Bryan Peterson" its a good introductary book to learning exposure and how to control it best for your shots. It has case studies as well to help reinforce the theory. It's not too complicated, but a good book should give you a good presentation of the whole subject as opposed to the bitty advice you'll get in the forums (bits will get glossed over - left out or - as above - mixed up --- Ps when in doubt listen to HelenB

 

[Ed Bray]

Not sure where you are coming from here, an 'f stop' is simply the size of the diameter of the aperture in the lens divided by the focal length (50mm lens with a 25mm hole = f2)

That might be just a little confusing, mightn't it? The f-number is the focal length divided by the diameter of the aperture (actually the diameter of the entrance pupil); and because f-number and the less well defined f-stop are often used interchangeably it could be confusing, especially to a beginner, to call the f-stop the 'size of the aperture divided by the focal length'.

Yes, I admit I missed out 'of the diameter' in the statement I made. My bad!

 

[Helen B]

Not sure where you are coming from here, an 'f stop' is simply the size of the diameter of the aperture in the lens divided by the focal length (50mm lens with a 25mm hole = f2)

That might be just a little confusing, mightn't it? The f-number is the focal length divided by the diameter of the aperture (actually the diameter of the entrance pupil); and because f-number and the less well defined f-stop are often used interchangeably it could be confusing, especially to a beginner, to call the f-stop the 'size of the aperture divided by the focal length'.

Yes, I admit I missed out 'of the diameter' in the statement I made. My bad!

Er, that wasn't what I thought was potentially confusing. It's the reference to the f-stop being the aperture/focal length rather than focal length/aperture, given that f-stop and f-number are usually taken to mean the same thing.

 

[Ed Bray]

That might be just a little confusing, mightn't it? The f-number is the focal length divided by the diameter of the aperture (actually the diameter of the entrance pupil); and because f-number and the less well defined f-stop are often used interchangeably it could be confusing, especially to a beginner, to call the f-stop the 'size of the aperture divided by the focal length'.

Yes, I admit I missed out 'of the diameter' in the statement I made. My bad!

Er, that wasn't what I thought was potentially confusing. It's the reference to the f-stop being the aperture/focal length rather than focal length/aperture, given that f-stop and f-number are usually taken to mean the same thing.

Oh, right, yes i see what you mean, I got it the right way around in the example, yes I meant focal length over aperture.

 

[Philoslothical]

1.)

For some reason the camera I have an issue with the camera focusing. No matter what I seem to do it sometimes doesn’t focus, and when I say that I mean there is no ‘beep’ sound with the green-light telling me it is set, thereby meaning if I click the shutter button down it will inevitably be distorted. I change the shutter speed, the F-stop?, etc. without luck. Looking through the viewfinder, the subject looks crystal clear, but the camera doesn’t focus? Other times it spontaneously focuses and I don’t know why? So much of my time with the extension tubes on is spent looking through the viewfinder, changing the angle and/or the settings, focusing the lens, and nothing happens?

Why is this happening?

The reason you're not always getting AF confirmation is because the extension tubes increase your effective aperture, meaning it increases the effective f stop used to focus (or, in simpler terms, it makes the lens function as if it had a much smaller maximum aperture).

The AF sensors in your camera are good to about f./8 if they're cross type sensors, and f./5.6 if they're the older type that is laid out in one direction only. Some cameras use both types, usually with cross type focus points near the center of the frame, and some weaker regular ones on the periphery. This is a limitation of the AF sensors and not a problem with your extension tubes.

The extension affects the max aperture of the lens you're using - not the f number you dial in, assuming the tubes have aperture linkage. The amount of extension will determine how much "slower" the lens becomes. There are ways to calculate this, but I won't go into that right now. The important thing is to understand why the AF confirmation fails, as you asked. The more intensely lit the scene is, the more you can get away with, generally. Other than that, all you can do is 1. use a faster lens, 2. use less extension, 3. stop relying on AF confirmation. I think #3 is the best option.

 

[Thunder_o_b]

Ok, a couple of things. You can photograph moving subjects at high mag handheld. I regularly shoot at 3:1 and higher handheld. But you will need a solid flash setup. LordV can even capture BIF's with the MP-E65 handheld.

"Sniper method" refers to long range shooting disapline. In short, you become one with the weapon. You learn to shoot between heart beats, and to use as few muscles as possible as each muscle used has a slight tremor. I shoot as the breath I exhale bottoms out my lungs. There is more (mind set etc) but you get the idea.

It is all rather Zen.