What might work best for me...

I have an application where I need a large depth of field and as low noise as possible. The subject is moving and in relatively low light and only 1-3 feet distance. Shutter speed has to be at least 1/160 and I can't use a flash.  If I switch to a small sensor camera - like a 1" sensor, I'll triple the depth of field at a given camera setting and the same focal length. Therefore, I can use a lower ISO to achieve the noise level I'm looking for. I don't think I need the extra resolution of the larger sensor since these images are for web-viewing only. 
I've been analyzing the pros and cons of each, but thought maybe someone else had a similar situations and has done the hands-on comparison.  So, is it a wash if I use a small sensor with greater depth of field at a lower ISO, or would there be an advantage, since I don't need the extra resolution of the larger sensor? 
I'm currently taking these shots with a k-50 and a K-3. Typically, the ISO is around 6400 at the aperture and speed I need. The photos are a bit noisy and noise reduction reduces detail too much.  I experimented with a K1 and the depth of field was so small that I had to reduce aperture size a lot - which gave me images similar to the others since the ISO had to go even higher to compensate.

McSpin wrote:

I have an application where I need a large depth of field and as low noise as possible. The subject is moving and in relatively low light and only 1-3 feet distance. Shutter speed has to be at least 1/160 and I can't use a flash. If I switch to a small sensor camera - like a 1" sensor, I'll triple the depth of field at a given camera setting and the same focal length. Therefore, I can use a lower ISO to achieve the noise level I'm looking for. I don't think I need the extra resolution of the larger sensor since these images are for web-viewing only.
I've been analyzing the pros and cons of each, but thought maybe someone else had a similar situations and has done the hands-on comparison. So, is it a wash if I use a small sensor with greater depth of field at a lower ISO, or would there be an advantage, since I don't need the extra resolution of the larger sensor?
I'm currently taking these shots with a k-50 and a K-3. Typically, the ISO is around 6400 at the aperture and speed I need. The photos are a bit noisy and noise reduction reduces detail too much. I experimented with a K1 and the depth of field was so small that I had to reduce aperture size a lot - which gave me images similar to the others since the ISO had to go even higher to compensate.

A crop of a larger sensor will give you the same result as a small sensor if they are covering the same scene and same perspective.  If the small sensor has more pixels than the cropped large sensor it mean high pixel density / smaller pixel size which probably means more noise.  A KP will give you 1-2 stops lower noise than your K-3 (based on my experience)

Doug

McSpin wrote:

I wondered about that, but the KP has a higher pixel density than the K-50, yet has lower noise. I was guessing that sensor technology was most important and that a recently produced sensor might be better.

In short... yes.

Doug

McSpin wrote:

MightyMike wrote:

If you can use a solid bright light source then maybe that would help you achieve the best result

I've tried that, but I'm taking photos of fish and they are frightened by the suddenly brighter light. I can put the light on for a few days and they get use to it, but that is too time consuming. I need the photos right away most of the time.

Maybe if you lower the water temperature they will swim slower and you can use a slower shutter speed 

Doug

DougOB wrote:

McSpin wrote:

I wondered about that, but the KP has a higher pixel density than the K-50, yet has lower noise. I was guessing that sensor technology was most important and that a recently produced sensor might be better.

In short... yes.

To follow up on my own post... I took a look at the Photons to Photos web site (http://www.photonstophotos.net/) and the KP at ISO 6400 has a "Photographic Dynamic Range" (their terminology) of 6.32, which is about the same as either the K-50 or K-3 at ISO 1600.  The K-70 is pretty close to the KP.

Doug

McSpin wrote:

If I switch to a small sensor camera - like a 1" sensor, I'll triple the depth of field at a given camera setting and the same focal length. Therefore, I can use a lower ISO to achieve the noise level I'm looking for.

Nope ... "duff science" I'm afraid.

Acceptable depth-of-field varies with sensor size.

If I take a "full-frame" lens and mount it on my APS-C (effectively half-frame) camera, the depth-of-field markings on the lens become "one stop out", that is to say, if I want "f/8 depth of field", as marked on the lens, I need to set the aperture to f/11.

As for photographing fish in a tank, I've done some in the past and don't remember any problems with flash disturbing the fish, though I do remember having to "try and try again" to get a result with no unwanted reflections. This was in the days of film, with no immediate gratification of instant preview, having to wait to get the film processed before I was sure I'd achieved what was wanted I have vague recollections of diffused flashguns on extension cables, but can't remember the details

McSpin wrote:

DougOB wrote:

DougOB wrote:

McSpin wrote:

I wondered about that, but the KP has a higher pixel density than the K-50, yet has lower noise. I was guessing that sensor technology was most important and that a recently produced sensor might be better.

In short... yes.

To follow up on my own post... I took a look at the Photons to Photos web site (http://www.photonstophotos.net/) and the KP at ISO 6400 has a "Photographic Dynamic Range" (their terminology) of 6.32, which is about the same as either the K-50 or K-3 at ISO 1600. The K-70 is pretty close to the KP.

Doug

After looking at this linked site, I was trying to figure out the relationship of dynamic range to noise, and don't see the connection. Can you explain this?

I am sure that my explanation will be corrected... But in this context think of photographic dynamic range as similar/related to signal to noise ratio.

From the web site: "The second test is for Photographic Dynamic Range (PDR).
This is a practical measure which incorporates all noise sources and targets a Signal to Noise Ratio (SNR) that is visually acceptable under standard viewing conditions.
PDR is the most popular measure published at PhotonsToPhotos."

(http://www.photonstophotos.net/Investigations/Measurement_and_Sample_Variation.htm)

Doug

McSpin wrote:

Using a flash is challenging because although it doesn't frighten this fish to an extreme, the images don't look realistically when the light is being bounce off the front of the fish (very reflective scales) vs coming from above, like it would from aquarium lights. I've experimented with this for years with tens of thousands of images and the best ones are with light from above that is bright enough. It's getting it bright enough without freaking out the fish that is the challenge. Part of that is because the aquariums are kept on the darker side on purpose.

I've done a little research into the methods I used ... the flashgun(s) were "face-up" in the aquarium hood, above the splash-guard, effectively in the same space as the normal aquarium lights, with diffusers fitted and the power settings adjusted to give just enough light for a good exposure. Nett result was very similar to the lighting from the aquarium lamps (flourescent tubes in my case), but the colour balance needed some tweaking in the darkroom ... it'd be a lot easier with Photoshop and a digital image! The flashguns would have been suitably waterproofed in plastic bags

Well, its not the sensor size that will affect the DOF, but rather the difference in focal length of lenses in this case. ISuppose you want to capture a 24mm FF-equivalent frame of view. A smaller sensor (1” or smaller), will have to use a tiny focal length in order to give you the 24mm FF-equivalent image. But, since you are not actually using a lens with 24mm focal length--- probably something like 6-8mm lens on a small sensor camera to get the same frame of view as a 24mm lens on a FF camera, your DOF is increased. So, the short answer to your question is YES, a small sensor camera will help you in this scenario, but not because of sensor size, rather the difference in focal lengths of lenses.