Is Comparing Image Quality Possible

There has been a vast amount of discussion in certain threads about the different image quality available from different cameras/lenses/formats/software/etc., which all goes to prove that there are a huge number of variables involved when it comes down to producing a digital image. Having tried to figure out a way of standardising a 'real world comparison' I've come to the personal conclusion that unless as many variables as possible were taken out of the test, then there will ALWAYS be room for argument!

So I thought that I'd take a different route, and hopefully others will follow too. Essentially I thought that it would actually be far more helpful to post an example of an image taken with a particular combination of equipment, processed to optimise (as far as this is possible) for viewing on the web. I make no excuses for trying to make the image look as good as I can (when viewed on my system) and others will have to decide for themselves whether this is successful or not.

However, here goes. The attached shot shows a long-clawed squat lobster (Munida rugosa) shot off the west coast of Scotland this summer in so so vis (~5 mish). Shot on a Canon 1DS in a Seacam with a 60EFS lens and 11mm MkII extension tube. ISO was 100 and the flash was a Seacam 250TTL used in eTTL mode. Avaialble light exposure was 1/100s at f/18 I think, set manually. I've included a 100% detail too. I have been asked about this lens set-up many times so the post may be useful to anyone interested in seeing how it works. Out of interest, the image was used (albeit small) in BBC Wildlife as a 'wild guess' within a few weeks of being shot!

If this idea is of interest, please post other useful shots too.

I think this is very useful Paul - thanks for posting. I'll try to post some other pix soon. Wideangle pix are also "fair game."

What works best is if you post a full photo, then a 100% crop from the center or area of interest, as well as a corner. The 100% crops should be about 400 pixels wide.

Cheers

James

Fabulous

OK. Here is another example - I should have said that the aim of this post was/is to simply show what certain lens/port/camera systems can do. Its up to those that view this to decide whether the combinations are/would be of relevance to their own underwater photography. The last shot was taken in poor conditions and was illustrating the shorter focal length lens on a FF Canon and its capability.

The shot attached to this post was taken in Monterey under the kelp and in not terribly bright conditions. Vis was probably 6~8m (?) -ish, so OK but not startling, but as anyone who has dived with these

seals will know, they can shift! My aim was to capture a good shot of a seal showing some degree of movement. Exposure was Aperture Priority at f/5.6 giving a 1/25s shutter duration at 200 ISO. Flash was full power from a single Nikon SB105 (NO diffuser). I purposely angled the shot to hold the seal - hence the angled kelp. The Lens used was my favourite wide-angle (on land or underwater) the 24mm f/1.4L series Canon on a 1DS, and this gave me a very bright image to view together with very fast, accurate autofocus - which was needed in the dull conditions.

Having tried to figure out a way of standardising a 'real world comparison' I've come to the personal conclusion that unless as many variables as possible were taken out of the test, then there will ALWAYS be room for argument!

 

I should have said that the aim of this post was/is to simply show what certain lens/port/camera systems can do. Its up to those that view this to decide whether the combinations are/would be of relevance to their own underwater photography.

Thanks for these, I think they are both great photographs, but they also demonstrate that quality is not everything. The first shot is undeniably great quality, in terms of sharpness etc, and is probably ideal to demonstrate the best abilities of your rig. It is a shot that might make one think 'I should change my DX to full frame'.

The second shot which is a nice photograph, does not demonstrate the best possible quality obtainable with your rig in my opinion, due to conditions etc, and I might think ' My DX rig can do that'

So to get back to your original conclusion regarding comparing rigs, the only real way to do actually compare the quality of various rigs is to to set up some type of static underwater set in a pool or perfect conditions, and take the exact same shot with each rig.

Come on Steve Frink, where are you, I'm sure you have tons of time to do this!

So to get back to your original conclusion regarding comparing rigs, the only real way to do actually compare the quality of various rigs is to to set up some type of static underwater set in a pool or perfect conditions, and take the exact same shot with each rig.

Hi Loftus

My conclusion is actually that its a matter of strengths and weaknesses of set ups rather than anything else. The second shot illustrates the capabilities of a very fast lens in less than ideal conditions. Its not all about absolute image 'quality', but more about using the appropriate tool to achieve an end result. Even if every variable is reduced to an absolute minimum, the conclusions to be drawn from a static test are still not 'real world'. Evaluating and demonstrating real strenghts and weaknesses is still difficult, but it is 'real world'. One thing which interests me (and given the current stupidity from airlines over carry on luggage, will probably interest others on wetpixel) is how to optimise wide lenses behind small domes - because it is a lot easier to travel with small domes, and I should have added that the second shot was also taken using the most compact dome port (the DP95 in this case from Seacam) I can get for this lens. My point was that using a fast fixed focal can make shots possible which might not otherwise be so. And 1/25s at f/5.6 and ISO200 is pretty dim illumination for AF to lock on and hold onto a fast moving subject.

I reckon that underwater photographers have never had it so good, and that most decent cameras (define as you will) are capable of excellent results, but some combinations work better in certain situations.

Paul, my fiancee's nickname is "seal" and she absolutely loved the way the seal turned his head towards the camera! And, I liked the composition of the angled kelp, too!

My question: Were you panning on that shot to get motion blur of the kelp in the background?

(more below)

(cut)

The last shot was taken in poor conditions and was illustrating the shorter focal length lens on a FF Canon and its capability.

 

The shot attached to this post was taken in Monterey under the kelp and in not terribly bright conditions. Vis was probably 6~8m (?) -ish, so OK but not startling, but as anyone who has dived with these

seals will know, they can shift! My aim was to capture a good shot of a seal showing some degree of movement. Exposure was Aperture Priority at f/5.6 giving a 1/25s shutter duration at 200 ISO. Flash was full power from a single Nikon SB105 (NO diffuser). I purposely angled the shot to hold the seal - hence the angled kelp. The Lens used was my favourite wide-angle (on land or underwater) the 24mm f/1.4L series Canon on a 1DS, and this gave me a very bright image to view together with very fast, accurate autofocus - which was needed in the dull conditions.

When I first saw the 100% crop, I was initially fooled into thinking that you were shooting at ISO 3200, the turbidity was so great. Since your 1Ds is very quiet, my question to you is that do you think the shot would have been better at, say, ISO 800 with 2 more stops of aperture & speed?

Always willing to learn more,

Dan

And 1/25s at f/5.6 and ISO200 is pretty dim illumination for AF to lock on and hold onto a fast moving subject.

correct me if I'm wrong, but isn't the auto-focus speed only dependent on the widest aperture of the lens, and not the settings that the next shot is going to be taken at?

scott

Yes there is substantial motion blur - a 'fast' moving subject at 1/25s frozen partially by flash (ISO 800 on a 1DS WOULD be noisy!!!), and....

AF speed and lock-on capability is governed by many factors but in this case the camera settings show how dull the light levels were, nothing more. I was simply trying to illustrate that I was usign an APPROPRIATE lens/camera/flash set-up for a particular type of image (fast aperture, medium-wide, fixed focal length lens in dull, relatively murky conditions), nothing more.