regarding DOF

[anandchhetri]

Just started taking photographs with my new D5000 and 18-55 kit lens and got loads of questions.

1.Using the lens that I have how do i get the background blurred? With my trials I get it when i use F5.6 . Is this the correct way of doing it??

2.If I want to take a lot of macro photographs, do I have the correct lens? If not which one will serve the purpose?

3.What is the difference between a prime lens and a zoom lens? From what i read it was written that in prime you cannot adjust the focal length whereas in zoom lens you can adjust the focal length.(If I am not wrong). But isn't adjusting the aperture same as adjusting the focal length? Where am i going wrong?

Thank u all in advance.

[RecurrentNerve]

Hi, welcome and well done for buying a great camera (I'm biased ). To answer your questions:

1. To blur the background you are correct in using f5.6. The larger the aperture, the shallower the depth of field, and thus the more blurred the background. If you look on top of your lens you will see it says '18-55mm 1:3.5-5.6'.

This means the largest aperture the lens will achieve is f3.5, when the lens is zoomed right back to 18mm, so you can blur the background a little more with these settings.

2. The 18-55mm lens is not ideal for macro photography, though you can still take good close up shots with it. For true macro you need a relatively expensive lens like the Nikon AF-S 85mm f3.5 G DX VR Micro lens. The main thing to look out for when buying lenses for your D5000 is the AF-S designation. This means the autofocus motor is in the lens itself; as the D5000 has no AF motor in the body itself this is essential, unless you don't mind manual focussing.

However, unless you're rich, I would recommend trying some close-up shots with your kit lens first of all. If you like it and get some good results, perhaps try some extension rings, which are rings that fit between the lens and the camera and increase the focal length allowing for closer-in shots. These are much cheaper - manual focus extension rings come in at around $20.

3. You are right in saying that a prime lens has a fixed focal length. Focal length is essentially 'zoom'. When your kit lens is zoomed right in, its focal length is at 55mm. Zoom out and it's 18mm.

The aperture is a different thing entirely. The aperture is the hole that lets light into the lens. The smaller the aperture, the less light comes in. As you know, a large aperture lets more light in and gives the effect of a shallow depth of field.

Prime lenses often have the advantage of having a much larger maximum aperture than zoom lenses. For example, the Nikon 35mm prime lens (so its focal length is fixed at 35mm) has a maximum aperture of f1.8. This makes it great for portraits because the large aperture gives a super-shallow depth of field, so your background will be really blurred. It's also great for low-light situations and indoor shots where you can't use the flash, because that wide open aperture lets lots of light in.

Hope that helps.

[zona5101]

Originally Posted by anandchhetri

Just started taking photographs with my new D5000 and 18-55 kit lens and got loads of questions.

1.Using the lens that I have how do i get the background blurred? With my trials I get it when i use F5.6 . Is this the correct way of doing it??

Experimenting and trialing is good. Your DOF will change with focal length as well as apreture. Check out Online Depth of Field Calculator Use the calculator and run some instances of distance, apreture, focal length ans observe how the near to far focus disatances change.

2.If I want to take a lot of macro photographs, do I have the correct lens? If not which one will serve the purpose?

If you indend to do a lot of macro work you should consider investing in a true macro lens.

3.What is the difference between a prime lens and a zoom lens? From what i read it was written that in prime you cannot adjust the focal length whereas in zoom lens you can adjust the focal length.(If I am not wrong).

Thats pretty much it in a nutshell...usually there are less optical compromises in a prime lens so they tend to be one or more of the following -sharper, clearer, faster, better color and contrast.

But isn't adjusting the aperture same as adjusting the focal length?

No. Have a gander at some of these articles...
http://www.digital-photography-schoo...-for-beginners

[mrteacherdude]

DOF: For a general overview of DOF I like this page - Controlling Depth of Field

Macro: If you start shopping for stuff to give your current lens better magnification, RecurrentNerve mentioned extension rings. These may also be listed as extension tubes.

Many people have good results from closeup rings (filters), which screw on to the end of your lens like a filter. However, they add another element of glass which could potentially alter your image; good ones are not necessarily inexpensive.

Another "cheap" way to go macro, but potentially more complicated, is to use an inverted (or reversed) lens. As near as I can tell from reading, most people use old, manual prime lenses in the 50mm range, but I don't see why you couldn't do it with other lenses. I'm currently playing around with an old 28mm wide angle lens I found in one of my old camera bags, and I rather like the initial results I'm getting. There are lots of articles and "how tos" on the internet about this (reverse mount), and to do it right will require a reverse mount adapter for your camera. Do be aware that this method is essentially more complicated than extension tubes or close-up filters, but the results can be quite stunning if done right.

Do be aware, as RecurrentNerve mentioned, that if you use (some types of) extension tubes or an inverted lens, you will be manually focusing your lens. Personally, I would play around with and practice getting close with the lens you have, and then try some other techniques as you get better at closeup stuff to see if you even like close-up photography before investing a lot of money in a macro lens. If your lens behaves similarly to the one I have, you will likely get better results at the 55mm focal length, and it gets you a little farther away from those pesky stinging ants

[anandchhetri]

Thank you all for the info...

This means the largest aperture the lens will achieve is f3.5, when the lens is zoomed right back to 18mm, so you can blur the background a little more with these settings.

I got confused here. ..so both f5.6 and f3.5 can be used?

and is the lens that I have a prime? How is it classified?

[anandchhetri]

Also when i read this article
Introduction to Aperture in Digital Photography

shallow depth of field is achieved at F4.5 and larger depth of field is achieved at F22.

Considering the lens that I have (18-55), I get a shallow depth of field at F5.6 than F3.5.
As I go back from 5.6(more zoom) to 3.5(less zoom) i get a larger depth of field( the backgrounds are not blurred enough).

Where am i going wrong?

[OsmosisStudios]

anandchhetri, I'm gonna answer everything all at once. But first, a deep breath.

*sigh*

Okay

In your first post:

1.Using the lens that I have how do i get the background blurred? With my trials I get it when i use F5.6 . Is this the correct way of doing it??

Getting a blurred background (or a shallower depth of field) is done mainly by using the largest aperture you can. This is the smallest number on the aperture scale, expressed as f/#. In your example, your 18-55 f/3.5-5.6 lens has a maximum (largest aperture) of f/3.5 at 18mm. This decreases to f/5.6 by the time you get to 55mm. So, if you look more carefully, the lens is an 18-55 ZOOM with a maximum aperture of f/3.5 at the wide (18mm) end and f/5.6 at the long (55mm) end.

If you're at 55mm, then yes, use f/5.6. If youre any shorter, then the number may change.

#2:

2.If I want to take a lot of macro photographs, do I have the correct lens? If not which one will serve the purpose?

No, you dont. Macro photographs require special equipment, but there are several options. The most common (and best all-around) is a dedicated macro lens. A dSLR isn't like a compact camera in that it cant do macro by itself: it needs the new lens. In the Nikon lineup, that's the AF-S 60mm f/2.8 Micro, the AF-S 85mm f/3.5 VR DX Micro or the 105mm f/2.8 VR Micro.

As I said, there are other ways of doing it: extension tubes, diopter filters and lens reversing. They're more complicated, but a quick search (either on Google or the forums here) should get you all the information you need.

#3:

What is the difference between a prime lens and a zoom lens?

A PRIME lens has one focal length that does not change. A ZOOM lens has a focal length range, from which you can choose any focal length. The advantage to a prime is that it is generally a larger-aperture lens so it allows more light. Being that it only has one focal length, it is also optimized for that particular focal length, meaning it's going to be very very good. A zoom is more convenient as you can carry one lens to cover several focal lengths, but most are smaller-aperture lenses and those that have larger apertures are expensive (and still arent as fast as some primes). These lenses do have another drawback: quality. Most zooms cant compete with primes, though that has changed in some cases.

From what i read it was written that in prime you cannot adjust the focal length whereas in zoom lens you can adjust the focal length.(If I am not wrong).

As you can see, your research is correct. There's just a bit more to it.

But isn't adjusting the aperture same as adjusting the focal length?

I'm gobsmacked. Literally speechless.

The aperture of a lens is the size of the opening at the nodal (where this is isn't important). If you want to think of it as a pipe, then the aperture is the diameter. The focal length is the length of the pipe.

Aperture controls how much light hits the sensor, while the focal length controls what is seen by the sensor. They're totally separate.

Where am i going wrong?

You need some more reading on the basics.

In your latest post, you mention that you get shallower Depth of Field (DoF) at 55mm f/5.6 than at 18mm f/3.5. While aperture is the MAIN contributor to this phenomenon, focal length does affect the DoF: longer focal lengths mean shallower Depth of Field.

So, if you're at 18mm f/3.5, you'll have a deeper DoF than at 55mm f/5.6. There's a very long-winded technical explanation of this, but you need a masters of physics to understand any of it (I still have trouble).

In short, at the same focal length, the aperture will control the DOF. So, if you're shooting at 18mm, you'll get a shallower DoF at f/3.5 than at f/5.6.

[anandchhetri]

In short, at the same focal length, the aperture will control the DOF. So, if you're shooting at 18mm, you'll get a shallower DoF at f/3.5 than at f/5.6.

This was the reason for my confusion as i couldn't get both f/3.5 and f/5.6 at 18mm. Do I have to use manual focus to get it??

[Eastree]

Originally Posted by anandchhetri

This was the reason for my confusion as i couldn't get both f/3.5 and f/5.6 at 18mm. Do I have to use manual focus to get it??

Manual r automatic focus have nothing at all to do with aperture. Adjusting the aperture changes based on what mode you're shooting in. If you're using shutter priority or aperture priority, you will adjust either shutter or aperture, and the camera will adjust the other, based on your ISO, to properly expose the metered area (expose as in make it that middle gray tone ... this gets complicated later on).

I suggest reading up on the exposure triangle.

You're really mixing up a lot of different things.


edit:
Focus: Determining what distance away from the lens, objects will be sharp in the image

Aperture: The diameter of the lens relative to its focal length; a way to determine the relative amount of light allowed into the camera. A wider aperture (smaller f/ number) yeilds a shallower depth of field.

Focal length: How "long" a lens is; it determines field of view and (basically) distance magnification.
A short focal length has a wide viewing angle exaggerates distances, and can cause distortion from fitting such a wide field of view into the space of the image.
A longer focal length compresses distances, is used to "zoom in on" farther objects (Zoom is in quotes because I cannot think of a better simple explanation. Of course a prime lens with a long focal length cannot zoom).

[Sterling]

Your zoom lens has different maximum apertures depending on the focal length you choose. At the minimum focal length of 18mm (as wide as possible) the max aperture is f/3.5. If you stay at 18mm the available f stops go up from there. You certainly can get both f/3.5 and f/5.6 at 18mm. f/3.5 will have the shallowest depth of field at 18mm.

At your lens' maximum focal length of 55mm (zoomed all the way in) the maximum aperture is f/5.6 and the available f stops go up from there. At 55mm, f/5.6 will give the shallowest depth of field.

In between 18mm and 55mm the maximum aperture will vary between f/3.5 and f/5.6.

I think this has already been stated above but it couldn't hurt to repeat it.