Question about aperture settings

I got a trip to the philippines coming up and have a basic kit lens. Generically, I'm trying to improve the macro without going out and buying a specific lens for that purpose. I understand the basic principles behind an f-stop. What I don't understand is what determines your highest available hardware f-stop inside the camera. IE most DSLR's I've read about go to f22 but I've read where others can go to a higher f stop. Is this determined by the lens or the camera?

On supermacro shots - is it better to use a teleconverter or a simple macro extension - The macro extender simply allows a closer focal point so I know there's a point of diminishing return.

Gary,

F-stop is a lens setting. Most folks are more concerned with the lowest f-stop on their lens than the highest - generally, the smaller the f-stop number (i.e., f/2.8), the bigger the max aperture, and the more expensive the lens. You'll hear a lens with a large max aperture referred to as "fast."

On supermacro shots - is it better to use a teleconverter or a simple macro extension - The macro extender simply allows a closer focal point so I know there's a point of diminishing return.

A teleconverter makes the lens longer at the expense of aperture/light - i.e., a 200mm f/2.8 lens w/ a 2x tele is now a 400mm f/5.6 (twice as long, 2 stops slower). A macro extension tube decreases the focal distance of the lens - that's what the old Nikonos used for macro - also at the expense of light. Which is better? Up to you - guess it would depend on what lens you were using them with, and what you were taking pictures of. The extension tube will be a lot cheaper generally. There's a third option - you could put a close-up diopter on the front of the lens; basically a magnifying glass. That'll also decrease the focal length, but without impacting aperture. It does decrease depth of field though. Option #4 would be to buy a true macro lens, which is the easiest way to do it.

hmmm...

Macro without a real macro lens is very limiting. Wet or dry diopters do increase the close focusing ability of a normal (non-macro 50mm) lens; but, a real macro lens is specifically designed for close focus.

f/stop for macro

-limited by the amount of power your strobes can pump out (when using low ISO 100); I usually shoot f/22 with my nikkor 60mm macro. (note: the lens will do f/32 and the bellows effect pushes that to f/64 when focused to 1:1.)

-the closer you focus the shallower the depth of field at any f/stop

bottom line = look at either for your camera:

-Olympus 35mm f/3.5 (relatively inexpensive, ~$165 at b&h after rebate)

-Olympus 50mm f/2.0 (more expensive; but, faster and more flexible for lighting)

How much are you spending on your Philippines' trip?

(how many shots will you miss without a macro lens?)

Take Care,

ChrisS

Thanks Tim and Chris,

That definitely helps.

Chris,

A new lens would mean a new port and big $$. I'm actually not spending too much on the trip to the Philippines. I won the trip (diving and hotel) and I paid for the airfare via mileage. I'm on a pretty tight budget and am looking at adding an inon lens holder that will allow me to put a wet lens in front of the port. I should be able to get some decent macro with just the lens I have (14-42mm). I've already taken it out and given it a shot; however, the tiny stuff and super macro is out of reach of the lens. I was trying to see if there was a way to make it a touch more versatile.

F./number.

An F./stop is the focal length of the lens divided by diameter of the aperture of the lens. ie It is a reciprocal scale. F./22 is 1/22 of the diameter of the focal length. F./4 is one quarter.

Once you get into back focus extensions in order to do close-ups of subjects within say 10 times the focal length of the lens, this scale is no longer appropriate and you have to make adjustments when extending the back focus as you do with extension tubes. Macro lenses automatically adjust (mechanically) the aperture rating as you rack them out to focus closely. That is also why the minimum and maximum aperture (hole) in terms of F./stop in a zoom lens alters according to the focal length (zoom) setting.

Close-up suplementary lenses work by shortening the focal length of the lens while maintaining the same distance between image plane and lens (back focus).

Does that help?

Before buying extension tubes make sure that they support autofocus with your setup. I use Nikon and as far as I'm aware there are no extension tubes that support autofocus with my setup, maybe it's diffeent with Olympus

The f-stop shown by a camera actually takes into account magnification. This is because exposure increases by a factor equal to (1 + magnification factor) squared.

So if you are shooting at lifesize on film/sensor, the magnification of the subject which is imaged at its own size on the film/sensor is 1, so the exposure increase is (1+1) squared = 4 - ie 2 stops different to infinity shots. So if you are shooting with the lens set to f/16 it will indicate f/32 when shooting at lifesize and if you are using closer using an extension tube which 'talks' to the camera then the aperture shown may be even smaller. This often causes confusion!

The f-stop shown by a camera actually takes into account magnification. This is because exposure increases by a factor equal to (1 + magnification factor) squared.

 

So if you are shooting at lifesize on film/sensor, the magnification of the subject which is imaged at its own size on the film/sensor is 1, so the exposure increase is (1+1) squared = 4 - ie 2 stops different to infinity shots. So if you are shooting with the lens set to f/16 it will indicate f/32 when shooting at lifesize and if you are using closer using an extension tube which 'talks' to the camera then the aperture shown may be even smaller. This often causes confusion!

We had a discussion about this on a dutch forum as well. I noticed that the Nikons displayed the actual setting (e.g. f/64 etc), while my Canon 20D limits itself to the "lens settings". Do the more expensive Canon models show the actual setting as well?

So essentially the camera might read the "real" aperture or just the hardware aperture depending upon the brand of the camera. Additionally, if for example, true aperture value is smaller with an exension then you probably need to make sure you have the strobe power to light the subject.

I think that what is shown on the Nikons may be referred to as the 'effective' aperture as opposed to the 'set' or 'actual' aperture on the Canons.

What is important is to realise that as you approach and exceed 1:1, you will need more light - this is especially important if using manual flash, but that said once you are used to a specific set up, then it becomes much easier to predict whether to add power. close in the flash(es), etc. Its a useful bit of applied photography to understand and utilise when required.

I'm sorry to go back to Gary's post, after all the high-powered stuff, but "good underwater images" and "kit lenses" don't really belong in the same sentence.

The D70's kit 18-70 zoom was quite good for fish, but only with a big port, a zoom ring and a diopter. Most kit lenses aren't wide enough or macro enough to get close, unsurprising when you think that they are designed to be cheap and shoot people or distortion-free scenes.

I guess that you could try a close-up lens or diopter if there's space behind a flat port to improve close-up images, but there isn't really an alternative to getting a macro lens and a port for macro images. It's cheaper than a fisheye and a dome, anyway...

I know quite a lot of divers who have done better with a compact camera: the wide-ness and macro-ness of their zoom lenses is often better than a DSLR's kit lens.

The other thing about macro (as if I was an expert, ha ha...), is light. A good strobe or two are pretty important, or the light just won't allow for any depth of field (ie an f-stop of f16-22), or to freeze motion. You need a shutter speed of 1/90 sec or faster with ambient light if you haven't practised a lot, but as a strobe freezes motion in the few milliseconds of its flash, you can work down to quite slow shutter speeds. You can get quite artistic at 1/15 sec, as some parts of the image blur, though lots of images just look, well, badly focussed.

Tim

B)

So essentially the camera might read the "real" aperture or just the hardware aperture depending upon the brand of the camera. Additionally, if for example, true aperture value is smaller with an exension then you probably need to make sure you have the strobe power to light the subject.

Yes, that's more or less the practical takeaway - you will definitely need to make sure you have the strobe power to light the subject. Keep in mind that you'll also likely need to set a high aperture to get any depth of field, which means lots of strobe power, and/or moving your strobe close enough to do the job.

To be honest, having been in your situation (budget-constrained and trying to shoot macro), rather than spend any more on ext tubes/etc., I might just do what you can with the Inon, and save up for the macro lens/port at some later date. Since it's a Wetmate lens, you're not locked into shooting only macro during the dive as you'd be with extension tubes, and you can use it w/ a macro lens in future to get to greater than 1:1. Also, at least for me, shooting with an extension tube on a non-macro lens was considerably more frustrating than shooting with a diopter.

Good luck, hope the trip goes well.

"I'm sorry to go back to Gary's post, after all the high-powered stuff, but "good underwater images" and "kit lenses" don't really belong in the same sentence."

You might be right and my search might be in vain but I have found an M67mount which will allow me to place a wet lens in front of the flat port. I'm not sure how ideal that will be underwater but I think from a cost perspective it hits the mark.