[Xarcell]

I have almost $100 to invest on my camera(Pentax K-X).

What do you think I should buy? I'm new to this and I'm trying to expand my horizon. I have a very small studio with a muslin backdrop 3 lights(2 umbrella).

I was thinking of maybe buying a macro lenses, or a wide angle lens, or a ring flash. Perhaps more studio equipment, I dunno...

Currently for my camera I only have a 18-55mm zoom lens and a 55-300mm zoom lens. I also already purchased a flash diffuser just to try out.

I like taking portraits and close-ups.

Any advice on what I should spend my $100 on?

[JeffJS]

Pentax-A 50mm F1.7 Reviews - A Prime Lenses - Pentax Lens Reviews & Complete Lens Database

$100 should easily land you one of these if portraits are your thing.

[RioRico]

Being a cheap bastard, I'll recommend scouring eBay for a cheap bellows, some cheap enlarger lenses (ELs), and some cheap adapters and tubes. I wrote https://www.pentaxforums.com/forums/pentax-lens-articles/152336-cheap-macro-b...lose-work.html to cover some of that. Some cheap items:

* M42 bellows, probably for under US$40 (the most expensive part of this kit).
* ELs around 75mm (for macros), 100mm (for macros and portraits), 130mm (for general short tele work). Those should be around US$5 each.
* Many ELs are M39 mount, so a cheap M39-M42 adapter (under US$5).
* A cheap safe flanged no-infinity-focus M42-PK adapter (under US$5).
* A cheap set of M42 macro tubes (under US$10).

For something totally else: an M42 Super-Takumar 55/1.8 lens (under US$50); the M42 tube set I mentioned above; and a good third-party infinity-focus M42-PK adapter (under US$20). The lens by itself is splendid for portraits and for very sharp general work. Put it on tubes and it's great for macros.

Both of these options are totally manual -- aperture and focus. They require a bit more work than your autofocus zooms. And you will learn a TON about photography, and have piles of fun! And they're cheap. I like cheap.

[Ash]

Good advice already.

Looks like you'd do well with a manual focus fast fifty. You probably don't need macro capability, but the fast fifty will produce excellent results for portraiture both in and out of the studio setting.

[calsan]

How about a tripod? Actually, $100 probably only buys 1.5 legs...
or
spend $100 printing your best portraits on nice paper to show people to get more portrait work.
More work = more money to buy nicer lens later on.

[KxBlaze]

How about saving up a bit more for the FA 100mm 3.5 or even a bit more for the FA 50mm 2.8 which are both dedicated macro lenses?

[Xarcell]

these are all good ideas, but I am still unsure as what to get. I forgot about getting a prime lenses somewhere down the road. Maybe now's the time...

Unfortunately I know nothing about aperture, but I guess now would be a good time to learn?

But I'm also thinking of building me a green screen on my small studio. perhaps by painting a section of the wall?

[bobbyscon]

I am always in this dilemma. What to get with my fun money?! There are so many choices there basically isn't a wrong choice to make!

If you're relatively new to photography, and based on "I know nothing about aperture", I assume that you are, thinking about doing green screen stuff might not be worth your time just yet. Green screen is an art in itself. You need proper lighting (on top of your 3 light kit) which can get expensive fast. It's all about keeping the green perfectly evenly lit behind the subject in a way that keeps the green 1 uniform shade and doesn't spill back onto the subject. If you choose to paint, make sure to research the correct green to buy (you can go expensive and get "green screen" paint, or cheap and get something very close at Lowes Depot, but it does need to be the right shade of green (or blue if you want to do blue screening). These shades were scientifically chosen based on their proximity (or lack thereof) to human skin and hair tones.

I love RioRico's list. Getting a small host of older lenses will not only teach you a ton about photography and lighting, it also opens up a whole new set of photography options for you which will really enhance your portfolio, which, as calsan points out, = more $ which = more toys. (As calsan also said, you need a tripod if you don't already have one, but I figured you do if you're already shooting with a light kit.)

Stay versatile and flexible. Have a lens kit that gives you as many options as you'd like. But just have fun with it!

[RioRico]

Unfortunately I know nothing about aperture, but I guess now would be a good time to learn?

Indeed. Here are the basics:

Inside the glass of a lens (usually) is some mechanism for controlling the amount of light passing through. This is the aperture. The most common mechanism is a set of iris blades that open and close. Aperture is measured in f-stops. The aperture is the ratio of iris opening diameter to lens focal length. If the lens is 50mm and the iris opening is 25mm then the aperture is 25/50 = f/2. This f-stop measurement means you can calculate exposures (and other stuff) without having to know exactly what the iris opening is.

OK, that was the tough tech part. The implications of aperture are: The smaller the iris opening, the less light gets through -- and up to a point, the sharper the image is! And the converse: The larger the opening, the more light passes, and the softer the image. A wider (larger) aperture lets you shoot faster action and in dimmer light.

Before anyone jumps on me, I'll admit to using 'sharper' and 'softer' loosely and inaccurately here. What actually happens is a change to the depth-of-field or DOF. DOF is complex, but it boils down to the range of distances of acceptable image sharpness. A tighter aperture (larger f-stop number, like f/16) produces thicker DOF, so the image might be sharp from 2m to infinity. A wider aperture (smaller f-stop number, like f/2) produces thinner DOF, so the image might only be sharp between 2-4m. DOF depends on aperture, and lens-to-subject distance, and many other factors that we needn't worry about right now.

Faster lenses (with wider maximum apertures) usually cost more to produce and buy than slower lenses (with tighter apertures). Of my manual-focus Fifty's (all bought used), my ultrafast SMC-K 50mm f/1.2 (commonly called a K50/1.2) was a good deal at US$250; my good fast SuperTakumar 50/1.4 was a steal at US$50; and a decent but slower M50/2 often WON'T SELL for US$10.
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So, pros and cons of faster and slower lenses.

FASTER: Costlier; more artistic control of DOF; often softer wide-open (at maximum aperture); able to shoot faster action and in dimmer light.

SLOWER: Cheaper; less DOF control; sharper wide-open; need more light or higher ISO (which introduces noise), or use with lethargic subjects.
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All this applies to prime lenses, those with a single focal length like 50mm. With zooms, whose focal lengths can vary (like the 18-55mm kit lens), it's even worse. For our cameras, the number of FAST zooms (faster than f/2.8) ever built can be counted on one hand. Numerous fairly fast (f/2.8) zooms exist. They are not cheap. Long ones are not small. Read the lens database here and prepare for sticker shock. But a used f/3.5 zoom may be MUCH cheaper than a used f/2.8 zoom, even though the aperture difference is only 1/3 f-stop. And zooms with variable maximum apertures, like a 70-200mm f/3.5-4.5 zoom, tend to be of somewhat lower quality than one with a fixed maximum aperture, like f/4.

Uh oh, those numbers again! F-stops are measured as this series: 1, 1.4, 2, 2,8, 4, 5.6, 8, 11, 16, 22. (These are multiples of the square root of 2. Don't worry about it.) Each stop passes half the amount of light as the next number. And this tells us how to adjust shutter speeds. So a lens at f/2 only passes half the light as the same or another lens at f/1.4; and to get the same exposure value, we need to double the time the shutter is open. So if the camera meter says to use f/1.4 at 1/100 second, and we want more DOF, we set the aperture to f/2 and the shutter to 1/50. I hope that's clear!

There's much more, like diffraction. If you use an aperture tighter than f/16, light diffracts around the iris blades and the image is fuzzier. Most lenses are sharpest around f/8, say in the f/5.6 to f/11 range. But if you want thinner DOF or just need to grab more light, you must open-up the aperture more. There are trade-offs, many many trade-offs. Every camera+lens selection, and every picture shot, is a problem to be solved. And that's why we're all nutz. Cheers!

We're all here because we're not all there.
--Anon.