February 25, 2011

by Gavin Seim: Updated 11/22/12. There’s a lot of confusion out there about resolution as it relates to making prints, so I want to help clear it up. I make mostly large prints and spend quite a bit of time studying factors that effect my image quality. Often I use a 5D MK II, which is 21MP. I also use 4×5 film because of it’;s vastly higher resolution. It scans in at closer to 200MP. But to start with lets use an average 18MP file as our example.

First let me say that digital has a long way to go in terms of resolution. Today’s camera’s are amazing, but lets get a perspective. Ansel Adams did much of his work on 8×10 sheet film. It’s hard to compare film to digital exactly, but using a good film he probably would have had a rough equivalent of around 400 million (mega) pixels. This makes our digital cameras look pretty paltry at times and it’s one of the reasons I’ve started working with 4×5 film for some of my projects, as it can give me  200+ effective megapixels when scanned (more of that on my pictorials website).

Say we have a full size file from a Canon 7D. The resolution of that file would be 5184×3456 pixels. About 18 mega pixels (roughly 22x less than that 8×10 film). Our file comes in at just over 11 x 17 at 300 PPI. Note that PPI and DPI refers to Pixels Per Inch or Dots Per Inch (a printing term). For today’s purpose I’ll refer to it as PPI as it’s becoming the more common term.

First and foremost, PPI and actual file resolution (or pixels) are not always the same. For example I could take our file in Photoshop and set the size to 30×20. Unless I told PS to Resample (or increase the resolution) of the file, the computer would now see this file as a 20×30. Only now it would show as being just over 172 PPI instead of 300 because the pixels have not changed or increased, which means there must be less pixel per inch when printed at that size – It’s still an 18MP file. I’ve just told the computer it’s larger in physical print size. What really matter however is if you have enough overall resolution. Here a screen capture to show how I was changing PPI. The PPI on each is different, but the pixel quantity is the same.

So what if I printed this file as a 4×6. I’m not sure why I would want a print that small (see the wall portrait article), but bear with me. At 4×6 our 18MP file would print out at just over 860PPI if we left it at full resolution. That’s a lot since most human eyes can’t see any difference above 300PPI. Bottom line, my file has more than enough pixels. Printing with that extra PPI won’t hurt anything. Though depending on the printer, all that information may not be used.

Why does all this matter. Well mainly so you don’t get confused. PPI has relevance in sizing and printing because it can quickly tell us something about how good our print will be. That brings us to larger prints and how this all relates.

Click for larger view – Gavin’s 30 inch canvas, Bull of the Mist. This a medium sized print. Taken in early morning at ISO 3200 made the detail on this slightly less, but it was needed for shutter speed. As you can see, the detail is good, but not flawless. The canvas helps give it an organic art feel. This was made from a file that was 5464 x 2732 pixels. It was up converted to 9000px wide before print. More about this image here.

Resolution VS Large prints.
This is where things get subjective. I’ll speak from my own experience as I regularly produce prints 40 inches and beyond. With our 18MP file we know we have plenty of information for a baby print. What about a serious print meant for the wall. Lets look at that 20×30 again. Lets go into the “Image Size” box of Photoshop and changing the file dimensions to 20×30, without altering the resolution as I did above. I left Resample un-checked which means I changed the print size but not the amount of pixels in the file. We’ll now have 172PPI at a print size of 30×20. Are you getting it? This is telling us how much information we have to lay on paper in terms of real life printed pixels – 172PPI is not bad. Most peoples eyes can probably see a bit more detail than that, but the print should still be good.

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January 22, 2011

Click To Listen>> Photography Podcast. PPS #74
Review in iTunesVote on Podcast AlleyDirect Podcast Feed

Today’s Host... Gavin Seim.

Today we’re going in depth on digital quality and the Six Keys to Image Quality. Gavin discusses what he’s learned about getting down and getting the best image quality possible from digital files.

Gav with the new printer. The image links to the post about it.

Podcast #74 forum discussion:

Notable Time Indexes:

  • 00:00 Introduction. The Challenge
  • 07:05 The Six Keys to Quality.
  • 26:07 Editing Process in depth.
  • 29:18 Film resolution thoughts. More process.
  • 49:05 Thoughts on cameras, sensors & lenses.
  • 51:23 The new printer. Canon IPF8300.
  • 56:52 Picks of the week (links below)
  • 59:20 Coming workshops and closing thoughts.
  • 1:04:32 The after show.

NOTE: The Pro Photo Show Christmas contest winners will be announced soon. Stay tuned.

The Six Keys to Getting Great Image Quality.

The Fuji X100 looks really good.

A look at RAW vs JPEG.

File degradation article.

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June 21, 2009

Image from Despair INC. Their funny people.

by Gavin Seim: How often have you walked from of a business, annoyed at the lack of service? Businesses close everyday because people didn’t care enough to please. No matter what you sell, you need to give customers a happy experience. As photographers this is especially true. We’re selling quality and an experience, not a piece of paper. Similar in many ways to a movie theater, so today I’m using them as an example.

Last night I went to a theater called the Majestic in Yakima WA. Yep, I’m naming names. This is one of the worst Theaters in Washington because they don’t care. Poor management and inexperienced kids run the show. This “could” be a really nice theater, but you can almost feel the chilling lack of interest the moment you walk thru the door.

I went to see UP with family (fun movie by the way). The last show of the evening started and about half way thru I went to grab snacks. I was met by dimmed lights and told by a group of kids around sixteen that they were closing and cleaning so they could go home. Questioning this, I was informed that the owners make the decision. Then one young employee proceeded to make snotty remarks saying she likes the way they do it just fine and that they have lives too! Not kidding.

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March 25, 2008

JPEG, TIFF, PSD, Successive Save, Save As, and more.

by Gavin Seim. Updated 11/11. There’s often confusion about what makes a JPEG and other files degrade, so I thought I would so a few a real world test. First let me say that simply copying, or viewing a file does NOT cause any degradation as people sometimes believe. If you copy and paste a file it’s simply a bit for bit cop. There’s no loss because nothing has been altered.

When you open, and then re-save a file is when things usually change. Even if you save at the highest quality JPEG settings you have still re-compressed that file when you save again. Unless or course your using an uncompressed file format to start with (TIFF for example). But even then there can be some quality loss version after version.

So how bad is a file damaged each time you successively save it. Well lets just say you should keep your originals. I’m not saying we can’t make revision copies (or file generations as I refer to them). But we should be aware. Below we’re going to look at the same image submitted to various torturous conditions and you can then judge for yourself.

These image are 700px. Click any image to see it at that resolution, or download all the images to compare them. Images that were opened and saved with “Save As” rather than “Save” commands are noted as such. If you want to join the discussion beyond comments here is the forum topic on this.

Original File
Original File.
open/save/close/100x
JPEG / Open / Save / Close / 100x -- Here I simply opened the file and saved it again 100 times. No pixel edits were done to the image, I just made a type layer and then deleted it so that PS would allow me to save. Apparently PS could tell that no pixels were edited and did not overwrite the unchanged pixels. Minimal or no degradation here.

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