£0.75 poster size photos @ Pixum (usually about £8 elsewhere) & 20 free 6"x4" prints

RightRevBod

Thanks for the answers regarding resolution. I was assuming 300dpi, which is 90,000 dots per square inch. For a 18" by 12" this give around 19 megapixels.

However, if you have tried it, then I will go by your results.

Highland_Lass_2

MSE_Jenny wrote:

The poster looks like a good deal. Postage seems to be £3.05 - I've never developed pics online and was wondering if that was steep or normal?

I've ordered pictures online a couple of times and £3.05 does seem steep to me. Was going to order a couple but the postage put me off.

Karnam

i have some pictures from my digital camera at 3.2mp is this good enough for a mega poster? also i have a physical picture id like to scan in and have done as a poster, would this by ok? would i need to scan it quite high resolution?

i think this is a really good deal as i was thinking of getting some pictures as smallish posters (is 12in not quite small for a poster?) as room decorations. do they have an option to print things off in matt for the posters? or do they come as giant glossy pictures? or as poster type things?

Kentish

Karnam wrote:

i have some pictures from my digital camera at 3.2mp is this good enough for a mega poster?

According to Pixum's website, the minimum resolution for the 12" format on special offer is 1800 x 1800 pixels but they recommend 4800 x 3600 pixels...

Your 3.2 mp should be fine I judging by other comments above

Highland_Lass_2

Am I missing something? Is there anywhere on the site to edit your photographs - i.e. crop, lighten etc. Did try to upload some photos but it took an absolute age.

seth

Kentish wrote:

According to Pixum's website, the minimum resolution for the 12" format on special offer is 1800 x 1800 pixels but they recommend 4800 x 3600 pixels...

Your 3.2 mp should be fine I judging by other comments above

Kentish is right you should be ok.

There is no hard and fast rule about image size and resolution. 2 picture of the SAME scene on say a 4 mega pixel camera might product different results when printed. The guidelines provide on this thread are spot on, but the only way to get a definitive answer for your camera and type of photo (remember camera apply different processing in different situations!) At 79p + P&P this is a good time to see what your 3, 4, 5, 6, 7, 8 MP can do!

Seth.

Fuller explanation for those who care…..

The reason for the vagueness in what is the minimum image resolution is due to 2 reasons.

1)[font=&quot] [/font]Manufactured quote “effective resolution” Fuji are famous for this. For example they might have a 4MP sensor but output a 6mp image. This practice is not as common as it used to be, but the fact is the number of mega pixel is a major factor when people purchase cameras.

2)[font=&quot] [/font]The camera takes the photo and then processes it and then compresses it using JPEG. These 2 steps can change the print characteristics dramatically for the better or worse! Remember JPEG is a lossy compression (like MP3 for sound) it throws away detail. This might not matter for snaps that are 6x4 but blow the picture up and you might see the effects of the compression. These “artefacts” number and nature depends on the pre processing of the image from the sensor and the compression settings and algorithms used by the camera’s software writers: The people who program the computers inside your digital camera. Clearly big names like Nikon, Canon, Casio, HP and Kodak can spend time and effort on the software in their camera. The cheaper cameras tend to have slower processors (these are cheaper!) and so do less processing. You will notice the effects of a slow processor, slow start up times, slow auto focus lock, and image quality may not be as good as some of the more recent camera with faster processors and better software.

3)[font=&quot] [/font]Cameras are just boxes for catching light. The business end is the lens, if you have a poor lens you might not see some of the flaws until you blow up the image. All lens are compromise but cheap lens will limit image quality. There is no point talking about resolution, without considering the lens quality. A good lens can even make a low resolution sensor produce crisp (though not high resolution) images even when blown up. This is possible by matching good optics, mechanics and great software. Casio and Canon do this very well. E.g. the Canon S1 is only a 3.2 MP camera but the images it takes at this resolution scale well even to A3.



Just as plugging an MP3 player into a high end hi fi might highlight some of the shortcomings of the MP3 track, blowing up a poorly compressed JPEG may show some it shortcomings. This is not a problem with cheap cameras it depends how good a job the software does. For example many of the more expensive camera early cameras had slow processors but the problems were minimised with lots of processing from the sensor to the JPEG code. E.g. the DIGIC 1 based Canons, I had an IXUS 400 which has a slow processor by today’s standards but could produce A3 prints without problems.

This is one reason why a 3.2 or 4 MP camera may produce a better picture than a new 6 or 8 MP camera.

If you want to know about JPEG these are some good sites. Though the maths can seem tough it is basically simple. Just as MP3 encoders take the full sound and remove part humand do not notice, JPEG takes an image from the sensor in the camera that has been processed to improve colour and edges etc and removes things we don’t notice in a picture!

What are the things humans tend not to notice in pictures? “ One of these is the tendency for the human eye to notice variations of brightness intensity much more than variations of colour in an image. The JPEG algorithm can take advantage of this by applying different rules for brightness and colour variations.

Another property is that real world images generally do not have sharp boundaries for brightness intensity changes and colour changes. This means that spatial frequencies detected within an image are generally low order, ie gradual change rather than quick changes over a localised area of an image.”

Remember that JPEG compression and image processing is not straightforward the difference between good JPEG software and bad ones is vast, and this is before you consider the image processing from the sensor to the JPEG encoder.

http://murray.newcastle.edu.au/users/students/2000/c9425349/section3.htm
http://www.prepressure.com/techno/compressionjpeg.htm

Example of a camera that is 5mp but can still product A3 prints.

http://www.canon.co.uk/For_Home/Product_Finder/Cameras/Digital/Digital_IXUS_500/

Karnam

thanks guys, what about the matt/gloss thing? do pixum do matt pictures?

pookie

have tried uploading photos but was transferring the picture forever and gave up in the end. why does it take that long? is it better to send photos by CD (but of course that would take even longer)?

seth

I tried the java applet but that gave a cannot connect error.
How are people uploading?
Anyone contacted customer support for them?

Alfie_E

seth wrote:

Remember that JPEG compression and image processing is not straightforward the difference between good JPEG software and bad ones is vast, and this is before you consider the image processing from the sensor to the JPEG encoder.

The compression algorithm for JPEG is pretty fixed. The only choice is in the quantization tables, but custom tables don’t provide much, if any, improvement over the pair defined by the standard. With the standard tables, it’s the single-valued quality factor that determines the level of compression and dictates the quality.

While both JPEG and MP3 both use Fourier-based transforms and psychological phenomena to remove information, the comparison isn’t so direct. MP3 doesn’t even give a standard for encoding, only decoding. There is huge choice in encoding. There are three different frame sizes and fourteen different bit-rates that can be chosen at will across the file, and there is complete freedom in the psycho-acoustic model chosen, with no absolute limit to its complexity. This is the reason for such variability in MP3 files, and the steady improvement in quality for a given overall bit-rate provided by state-of-the-art encoders.

But, otherwise you’re right. It’s poor optics and noisy detectors that spoil the images in cheaper cameras.