selmslie Loc: Fernandina Beach, FL, USA

Each pixel each occupies a discrete location in the image. The ones near the center hardly move at all while the ones near the edges move more.

Think of them as mosaic tiles. They will end up in a regular pattern after they are moved. The ones near the center may move less than one pixel in distance.

Think of it as a huge Chinese checkers with each position occupied by a single uniformly colored marble. After rotating the image, the board will not have moved. If you only moved the marbles without interpolation, the ones near the center would not move at all and the others would move by one or more discrete units. With or without interpolation the image would necessarily degrade.

UtahBob Loc: Southern NJ

These are not vector files so when the image needs to get shifted, the program has to figure out what each pixel needs to be and since you're rotating rather than shifting right/left and up/down some parts of the image will move more than others.

Since this camera will shoot raw, I'd suggest doing that and then straightening and corrections prior to creating jpg output. I'm not familiar with the interpolators in Picasa but perhaps there is a choice available when performing resizing and rotation that will provide better output. The better interpolators are generally slower.

With jpg you should see degradation with each iteration of saving. Some programs will also do a lossless 90 degree rotation - i.e. moving the pixels relative to each other as you suggested. I can't find an old web page that had great samples but this is informative: http://www.cambridgeincolour.com/tutorials/image-interpolation.htm

Dlevon Loc: New Jersey

You have the right answer! There is pixel averaging.

farmerjim Loc: Rugby, England

I make Sharpening and noise reduction the last two things I do in PP.

malco555 Loc: Kenilworth UK

Pixels are not moved relative to each other Steve! It's not simply rotated. The pixel arrangement in any software is always defined as horizontal and vertical rows of pixels. The software therefore has to interpolate (calculate) new pixels based on the existing image and degree of rotation and basically create a completely new image from that information. With a high pixel count image you won't often notice the difference at normal viewing size, but a low resolution image will suffer badly by being rotated.

Phreedom Loc: Kitchener, Ontario, Canada

http://www.cambridgeincolour.com/tutorials/image-interpolation.htm

Interpolation... occurs each time you rotate or distort an image. The previous example was misleading because it is one which interpolators are particularly good at. The ...image below...shows how image detail (sharpness) can be lost quite rapidly:

The 90° rotation is lossless because no pixel ever has to be repositioned onto the border between two pixels (and therefore divided). Note how most of the detail is lost in just the first rotation, although the image continues to deteriorate with successive rotations. One should therefore avoid rotating your photos when possible; if an unleveled photo requires it, rotate no more than once.

The...below...results use what is called a "bicubic" algorithm, and show significant deterioration. Note the overall decrease in contrast evident by color becoming less intense, and how dark haloes are created around the light blue. The above results could be improved significantly, depending on the interpolation algorithm and subject matter.

And thus you lose some sharpness.

RealBohemian Loc: Toronto

It crops automatically,there is cropping Sarge ,that is why comparing pictures after process show different size, usually smaller.

RichieC Loc: Adirondacks

You are asking the program to "re-draw" the image, with the pixels all moved about the pivot point. This seems intuitive to us- but it isn't really straightening a piece of paper. The pixels are all square and level in the original photo, like a brick wall.

IF you had to straighten a brick wall, either the bricks are now at an angle- or you'd have to take it apart and rebuild it. It is never as nice, as some of the pixels will be in a place where another one is now, progressively farther then they originally were as you get farther from the pivot point. And as JR1 pointed out, if it remains the same size, only straightened, then you may have re-sized it too.

Whoops, someone answered this before I got to it...

gessman Loc: Colorado

All of this bother can be eliminated when an image is made. Cropping at the point of shooting is better than cropping later. You have a 50x zoom. Use it to your advantage. Boats on land do not have to sit level but waterlines do. So, when you shoot, pay attention to get level that which has to remain level and let that which does not have to remain level be not level. Abide by nature not somebody who may have been drunk parking his boat on a cliff. If you need the boat level and cannot shoot it that way without messing with Mother Nature, zoom in and take a shot of the boat leaving nature out of as much as possible. That way you won't have to concern yourself with it later. Our minds fix all these problems for us naturally but your mind is the only one your camera has.

You must learn to see in pieces in advance to avoid having to later compensate for not seeing beforehand. It's much like what I suggested to you earlier about your deer shots - whether you want them to appear free, wild, and in nature or tame and behind a fence in a pen. At first, it takes time to think these things through but it becomes second nature later with practice. You'll get it. Just look and think. Don't be lazy just because you have "post processing" on your side. That should be a last resort in your thinking.

the Scottsman Loc: Roseland, new jersey

Lori, I just did it in Photoshop and it look ok. Just did it by eye.

saichiez Loc: Beautiful Central Oregon

I suspect your problem as you describe it might be the viewing function as it operates when you view in Picasa.

If you make the changes in Picasa and see these distinctions, I suggest your do your "pixel peeking" (viewing for critical comparison) outside of Picasa, such as in your Operating Systems image viewer. You may not see these differences you speak of. If you have not tried that, it's worth a try. Even looking at the original AND the edited version in another editing program will confirm if there is really a problem besides the way that Picasa displays images.

I have seen similar statements and complaints about Picasa with regard to view changes. Particularly with regard to a view shift that takes place when opening files.

Picasa may work for the functions, but may show the results with differing views.

Picasa is a very nice and quite "dumbed down" image editor, and sucks as an organizer. But hey, it's free. If one is going to be critical of the finer points, perhaps spending a few bucks is not such a bad thing, as in buying a more capable image editor.... Elements comes to mind.

Picasa is great for what it does do, and that's fine. But it is what we call in the industry a "casual" photo editor. I'm not saying abandon it if you get what you want from it. I am saying you should test those two images against each other WITHOUT viewing them for differences IN Picasa. It is surely not a professional product, and probably most of us don't need more.

However, if you are going to get critical, and not test your results, perhaps the small faults in Picasa and the far less editing capabilities are not going to satisfy you.

I do hardly any post processing, and when I do need a Quick and Dirty simple process, I will use Picasa. When I am going to be critical, I either use Photoshop Elements or Faststone Image Viewer, which both have more complex learning curves.

Just depends on what will satisfy you the best. Free and relatively easy to use is a very good solution, sometimes.

GESSMAN is quite right. More care and a thorough knowledge of your camera's capabilities is important. Composition particularly should be done in the viewfinder in a way that eliminates cropping, leveling, and other composition features as much as possible.

As many are starting to rise to on UHH, the more "Right You Get it In The Camera", the less you degrade the quality in POST PROCESSING or Image Editing.

I might ask one last question... and it's definitely related. Are you using any physical stabilization, such as a tripod or monopod, which aside from reducing focus and shake problems, also give you more time to compose the image. The sailboat could have certainly benefited from these practices.

I still think you may be chasing a view function in Picasa that really does not exist in the pictures, viewed outside of Picasa.

saichiez Loc: Beautiful Central Oregon

I'll make one more point here, and it also relates to the composition in the view finder.

The sail boat is not level in the first place and should NOT have been leveled in the second pic.

If you look at the real horizon.... the water and mountains, the sailboat is not level in either on. If you wanted the sailboat level, the real background should not have been included. In both pictures the tilt of the lake/mountain background looks unnatural.

That's it... I've done the damage I logged in to do today.

mwsilvers Loc: Central New Jersey

That's true. Straitening always requires some cropping. The greater the amount of straitening, the greater the crop. In this case the amount of the crop was not huge but I downloaded the files, and the cropped version was not much more than half the size of the original, meaning lower resolution. I also looked at both at the pixel level and the sharpness, to my eyes, was very close. I think the "issue" here is the OP's expectations. In the cropped version there is less pixel density per square inch, precisely because its a cropped version. If the OP cropped the original to the same degree as the straightened version, I believe they would look equally sharp.

LGilbert Loc: Earth

Picture elements that change to a greater angle from vertical (ie - more diagonal) will lose resolution. It is simply a matter of math. If the mast had (just an example for clarity) a total of 300 pixels/inch sitting vertically over a length of 1 inch in an original photo with a crooked horizon line and you, subsequently, rotated the picture 45º (I exaggerate for example sake, but the amount of effect is linear from 0º rotation) to straighten it, the number of pixels over the length of the mast will decrease. Let's look at it another way. If the picture grid was a checker board of 8X8 pixels and the mast was vertical covering the whole row than the number of pixels would be eight for the mast but the horizon was crooked. Now lets shift the mast as we straighten the horizon such that the mast was now at 45º from vertical, but its step (base) was sitting on the same corner square, then the number of squares it covered over its length is now 8x.707 or about 5.6 squares for the same mast length. You would, therefore, lose resolution, both in contrast and, potentially, color depth and resolution.

Additionally, the edge of the mast, previously well defined (in our example) by the vertical grid structure of the sensor pixels, now require adjacent diagonal pixels to contribute to the resolution. Thus the amount of information required to maintain the crisp line has more than doubled.

The camera algorithm that dithers the sensor output to produce edges as close to the original subject uses information as necessary to duplicate the original sensor data/image to the memory. When you rotate you do not have the advantage of the original sensor data upon which to apply the algorithm again, and are now stuck with the data/color assignments of the original camera processor's distillation of the sensor data. Had the mast been at the desired angle initially, that processor would have blended the sensor data differently.

Thus, the higher the resolution the original sensor, the closer to attaining an image that can be rotated with minimal damage. Picture elements that were vertical (inline with the sensor maximum density/inch) will suffer when rotated to a diagonal position. Picture elements that were diagonal and, subsequently, rotated to a vertical position will gain pixels upon which to attempt to match the original processor algorithm's interpretation of the sensor information.

However, pixel count does not completely indicate the ability to non-destructively rotate. How well the processor can differentiate color gradations is critical in rotation as cruder color depth limits the ability to approximate the information onto a new set of greater or lessor number of pixels upon rotation.

Thus, rotation will degrade an image, however whether you notice it depends upon a number of factors, pixel count, color depth and, certainly, enlargement. If you are going to rotate an image and then display it upon a monitor or the Internet as the target display media, then rotate it at the maximum resolution before you adjust the pixel count to match the native density of your screen or the current Internet standard (72 dpi) for the average monitor. That way, you will gain the most information possible for the rotating program to attempt to approximate the original color gradations.

marcomarks Loc: Ft. Myers, FL

It's still cropping though, although it's doing it without your intervention.