Sigma 135 400
Can you please critique my photos??? EASY TEN POINTS?

i use a Pentax *istDL with a Sigma APO 135-400 mm lens.

just from what i can see, these are pretty good photos. you should definitely keep progressing and mixing new objects into your photography. try some nature pics – those are always sweet. my favorite picture was “line up”. i think these are good – some are a little blurry – but if you keep it up you’ll definitely get ‘er done.

Sigma 135 400

A quick definition of stock photography might be helpful here. The wikipedia entry says that it consists of existing photographs that can be licensed for specific uses. Book publishers, specialty publishers, magazines, advertising agencies, filmmakers, web designers, graphic artists, interior decor firms, corporate creative groups, and others use stock photography to fulfill the needs of their creative assignments.

There are many big stock photography sites online. A quick search on Google returns popular names like corbis, fotosearch, comstock. The businesses prosper by selling photos at different sizes, as the client specifies.

The prices for these sizes vary to suit everyones needs: for small images the price is low, but these can mainly be used only on websites and other mediums that don’t require great resolution. The expensive large sizes are suited for printing, displays, posters etc. We’ll talk more about this price – size dependence. Here’s a plot depicting the price vs size dependence.

The blue line represents a plot of the price of an image found on stock photography sites (average price for the mentioned sites) versus the image size (in megabytes). The red line represents the best linear fit. This gives a trend for estimating larger size prices. The megapixels of the photo can be calculated by dividing the size in megabytes by 3.

A more detailed view of the data used can be found in the table at the bottom of the page.

The resolution of the photos can be derived from their size (in MB) like this:

640 KB - approx. 640 x 480 pixels; 8.9" x 6.7" at 72 ppi
2 MB - approx. 1024 x 1280 pixels; 14.2" x 17.8" at 72 ppi
14 MB - approx. 1700 x 2550 pixels; 5.7" x 8.5" at 300 ppi
32 MB - approx. 2800 x 4200 pixels; 9.3" x 14" at 300 ppi
50 MB - approx 3400 x 5100 pixels; 11" x 17" at 300 dpi

Using the linear estimator from the figure we can calculate the price for a 150% and 200% times larger image. These factors are considered in the zoom column from the table below. The size in megabytes has a quadratic dependence on the zoom factor. Let’s take the 200% zoom (from 8 to 16, respectively from 60MB to 240MB) for example. This means that the new size will be 200% the width * 200% the height of the photo. This gives a 4 times larger photo (60*4 = 240 MB).

zoom  MB  price
1      1    211
8     60    476
12   135    813
16   240   1284

We get that by doubling the size of the image we triple the price. It amounts to a 1284-476 = 808$ difference in price. The sites don’t offer these large sizes. It’s not that they are not needed, they actually are. But there are no such powerful sensors (cameras or scanners). It would require a 240/3 = 80 megapixel sensor. Professional cameras go as far as 20 megapixels. That doesn’t mean there are no higher resolution images. Several photos can be combined in panoramas and such.

So let’s just suppose that the linear trend holds. If upscaling photos and maintaining just 66% of the original quality this means doubling the price of the image (3 * 0.66) and a 400$ difference. So, doubling the size of a good quality image, of about 20 megapixels costs about 400$.

We’ve considered the worst case scenario, and still there is great value added by upscaling photos. The algorithm at reshade.com makes possible the above mentioned quality upscaling and on many images it works even better.

Vlad Hosu is the founder of http://reshade.com

Here you can make your own wallpapers for free. Enlarge any image without losing quality.

Best ultra telephoto for under $400?

I am looking for an ultra telephoto lens (more than 300mm) for under $400. I have a Nikon D1H so the cool thing is that I can mount all the 35mm lenses on my camera. I found 2 lenses for around $400, both about the same price, which one is better? Sigma 135-400mm f4.5-5.6 or Tokina 80-400mm ATX f4.5-5.6? Or, if you know of anything better for that price, let me know. Thanks

Tokina 80-400mm f/4.5-5.6 AT-X Pro D Auto Focus Zoom Lens is good choice for you