Photography - Technique and Equipment considerations

[CJ]

When you muck about with an image and save it you will often be asked something like the Quality or the compression you want to use. Jpeg images are what are called 'lossy compressions' that means once you have compressed them you don't get back all the information that went into them, you get back an 'approximation' of what you put in. How good that approximation is depends on the quality of compression you use. On Photoshop the compression starts at 12 (big file, good quality) to 0 (small file, poor quality). In the examples below I have copied the same image 13 times (0 to 12) and resized them all to 400 pixels wide than I have saved them at the 13 available quality setting, starting at the top with 12 and working down to 0. The table shows the file size for a given quality.

Compression vs File size.
12 93K
11 67K
10 49K
9 40K
8 34K
7 28K
6 29K
5 25K
4 23K
3 21K
2 19K
1 18K
0 17K


Watch the cross on the top of the little tower slowly disappear and the blocks of colour starting to appear in the grass. For screen work (all the stuff I have posted here) I use quality level 7 as it appears to be a reasonable compromise between quality and file size.

12


11


10


9


8


7


6


5


4


3


2


1


0

[FBM]

Ah-ha! I'd suspected something of that sort would happen, but didn't have anything solid to go on. I always do the max, based on the assumption.

Whey you resize a photo, what are you losing? Does it reduce the quality?

[CJ]

Whey you resize a photo, what are you losing? Does it reduce the quality?

Imagine a square made of 4 spots, two black and two white, it doesn't matter which are which colour. Imagine making one spot from those 4, you end up with one grey spot. When an image is resized this is what happens all over the frame, not quite as crudely as that but you get the idea. That illustrates what happens when you reduce the linear width of an image by 50% you reduce the pixel count by 75% so effectively 75% of the fine detail goes too. The resize algorithm does it's best to keep the pertinent information.

Printing requires 300 dots per inch (dpi) for good quality, 600 DPI for very high quality anything higher than this is not discernible by the human eye at normal viewing distances. Screens can get away with 72 DPI, going beyond that is, at the moment, is a complete waste of time.

[FBM]

First experimental shots. Nothing was done except resizing. No UV filter.
Old Tamron:


New Sigma 120-400:


I'm at "work" now, or I'd do something a little more revealing about the differences. I just pointed out my office window, over the parking lot this time.

Screw waiting. I stepped out back and did this comparison:





EDIT: OK, I've had some time to learn the lens now, so tomorrow will be my first excursion. Hope to have something better than that to show...

[CJ]

The left of the image below is as it was posted by FBM, the right has been tweaked as described below.



In Adobe Photoshop Elements follow Enhance > Adjust Brightness/Contrast > Levels... and you will see the Levels dialogue box. Look at the three little pointers on the x axis of the graph.



The pointers are at the left, right and middle, look how they have been moved in the image below.



Notice how this has increased the contrast in the image.

Next for a little more colour. Follow Enhance > Adjust Colour > Hue/Saturation and you will see the Hue/Saturation dialogue box.



All I have done is add 15 points to the saturation slider. You can just type the number in rather than faff around with the slider.

Finally I have added a little Unsharp mask.



Here is the difference again.

[FBM]

wow. Thanks, CJ! I've been thinking about invesigating those tools lately. Now I'm motivated to do so before I ever post another picture. Damn. For starters, I'm going to rework the photos of that little old lady. I'll share it with you when I'm done.

Here's the original of the above, just resized slightly, nothing else:



My initial enhancement (compare with CJ's improvements):

http://api.photoshop.com/home_dbb96af8e ... 236899c7f4[/imgc]

Edit: Do you think I took it too far with the little old lady?

http://api.photoshop.com/home_dbb96af8e ... 862e1bc467[/imgc]

[FBM]

I'd like to hear anyone's opinion on this question: If I were to switch my Tamron 28-80 for a Sigma 28-80 (all else being equal), would there be an improvment in the images?

[CJ]

I'd like to hear anyone's opinion on this question: If I were to switch my Tamron 28-80 for a Sigma 28-80 (all else being equal), would there be an improvment in the images?

Which Tamron 28-80 and which Sigma 28-80? Please would you add the aperture details as there are various models.

[FBM]

I'd like to hear anyone's opinion on this question: If I were to switch my Tamron 28-80 for a Sigma 28-80 (all else being equal), would there be an improvment in the images?

Which Tamron 28-80 and which Sigma 28-80? Please would you add the aperture details as there are various models.

Ah, well, I was speaking hypothetically, of course. I guess my real question was more, 'Are all Sigma/Nikon/etc. (high-end) lenses superior to the cheaper Tamron?' I gather from your answer, though, that some Tamrons produce images of at least equal quality. That pretty much answers my real question.

[CJ]

Canon, Nikon, Sony (ex Minolta), Tamron and Sigma all produce lenses of different quality 'bands' eg a 'price fighter' for inclusion in kits and consumer market, some stretch to a 'mid range' for upper amateur and occasional professional use and then a 'top end' range for solid professional use. So just be aware which 'band' you are buying in. Photography is definitely an area where in general price is a good indicator of ultimate function.

Tamron started the trend to 'Super zooms' they were the first to produce a 28-300mm these lenses are great for day-to-day tourist travel type shots but the huge zoom range creates design compromises all over the place. Personally I have a short zoom (18-70mm), a long zoom (70-300mm) and a Macro and a bit like Thunderbird 2 I choose which Macro I take with me. I also have one very 'fast' lens a 50mm f1.4 which give me a very good low light capability. I am actually very happy with the 18-70mm Sony it does perform better than the Canon and Nikon kit lenses in tests but it is the lens I would replace if I had the money.

Tamron short top-end zoom.

Sigma short top-end zoom.

Nikon Professional short zoom

Nikon short/medium zoom upper consumer

Which short zoom lens do yo have at the moment?

[FBM]

Canon, Nikon, Sony (ex Minolta), Tamron and Sigma all produce lenses of different quality 'bands' eg a 'price fighter' for inclusion in kits and consumer market, some stretch to a 'mid range' for upper amateur and occasional professional use and then a 'top end' range for solid professional use. So just be aware which 'band' you are buying in. Photography is definitely an area where in general price is a good indicator of ultimate function.

Tamron started the trend to 'Super zooms' they were the first to produce a 28-300mm these lenses are great for day-to-day tourist travel type shots but the huge zoom range creates design compromises all over the place. Personally I have a short zoom (18-70mm), a long zoom (70-300mm) and a Macro and a bit like Thunderbird 2 I choose which Macro I take with me. I also have one very 'fast' lens a 50mm f1.4 which give me a very good low light capability. I am actually very happy with the 18-70mm Sony it does perform better than the Canon and Nikon kit lenses in tests but it is the lens I would replace if I had the money.

Tamron short top-end zoom.

Sigma short top-end zoom.

Nikon Professional short zoom

Nikon short/medium zoom upper consumer

Which short zoom lens do yo have at the moment?

I still only have two lenses. I'm trying to do my research before I add to the kit. That's good info about the 'bands'. I read up on compromises that long zoom ranges involve, so I don't want to do that. I'm satisfied with what the Sigma is giving me, even though that's a pretty long range itself, so now I'm looking at short and mid-range. The Tamron is AF Aspherical 28-80mm 1:3.5-5.6. Come to think of it, I haven't even read any reviews on that one yet. Thanks for the links. I'll get right on studying them.

[CJ]

The Tamron is AF Aspherical 28-80mm 1:3.5-5.6. Come to think of it, I haven't even read any reviews on that one yet. Thanks for the links. I'll get right on studying them.

This lens ?
Ok the main issue with this lens is the 28mm end which represents 37mm in old 'film' money. I would say this does limit your creative capability as you lack a good wide angle which given the preponderance of architectural and landscape photography. You need a lens with a 16 to 18mm short end.

[FBM]

The Tamron is AF Aspherical 28-80mm 1:3.5-5.6. Come to think of it, I haven't even read any reviews on that one yet. Thanks for the links. I'll get right on studying them.

This lens ?
Ok the main issue with this lens is the 28mm end which represents 37mm in old 'film' money. I would say this does limit your creative capability as you lack a good wide angle which given the preponderance of architectural and landscape photography. You need a lens with a 16 to 18mm short end.

Yep. That's the one. Yes, it sure does limit what I can do. 16-18mm short-end tip noted. I very nearly bought something today, and now I realize that it wouldn't have helped me in the least if I had. Now you're saving me money!

[Taryn]

Wow CJ, this shot is stunning.

Sorry I didn't reply to your post sooner, I've been playing with my camera.

These are the three pics, the first two that I posted earlier in the thread plus the one that I adjusted as you suggested.

Original

[CJ]

Welcome back Tryan I had guessed that you were occupied with your new toy!!