Sensor Electronics

[xpatUSA]

I'm not and expert nor and engineer. I did remember reading some materials on the DX vs FX (crop vs full frame) sensors and I seemed to remember something about overall quality.

The basic premise seems to be that the bigger the individual sensor (not the full sensor board, the individual sensors on that board) is for a given pixel produced, the more light will hit that individual sensor producing a higher quality result.

I'm not saying any of the above is right or wrong, especially from a pure technical aspect, but I think it is saying that bigger sensors have the capability of producing a better result in general. For example a 24MP DX vs a 24MP FX will have the same number of sensors on the board, but each sensor on the FX format will be larger and therefore will have more photons strike that area in a period of time as compared to the DX format. This should produce higher dynamic range and lower noise. At least, that's my very much a layman interpretation.

Just for interest, here are the words of a well-respected expert, Falk Lumo a.k.a. @falcon eyes:

http://www.falklumo.com/lumolabs/art...alence/ff.html

Warning: long sentences, graphs and formulae, sorry.

Opinions on this complex subject have a tendency to be brief and often skim the surface with no good references. Falk's articles, on the other hand, usually dig deeper than anyone here would care to go.

[billtils]

Every answer leads to a new question ...

The "shall I switch the D7100 for a D610" started a couple of months ago when I went on a wildlife workshop that led to exploring BIF. I use a Nikkor 70 - 300mm zoom, 4.5 - 5.6 lens, which works very nicely as a 400 on the DX. but I still have to crop to about 50%. A 400mm is not encompassed by the terms of the "domestic war and peace" budget, so the question is will using the 300 on a D610 produce any improvement when it comes to the product of cropping? As an illustration, the attached is cropped to approx 30% of the original

(I think the answer is "no of course it won't", but thought it worth checking).

[Manfred M]

Just for interest, here are the words of a well-respected expert, Falk Lumo a.k.a. @falcon eyes:

Falk's writeup is good, but is based on the math and physics side of the house. On the flip side, I don't think he has a good grasp of the design, manufacturing, financial, etc. side of things. I think he makes a lot of good points, but also some rather suspect ones.

Where I clearly see a miss is the cost of introducing fast, quality lenses on a crop frame sensor that give the user the equivalent depth of field of a full frame camera (which incidentally was one of the reasons I went full frame). Optically quality on so called "professional" lenses means even more constraints on the lens designer. Most pro zoom lenses have maximum apertures of f/2.8 and generally have zoom factors of less than 3x. Going to an APS-C sized sensor for the same DoF means that we would need f/2 lenses. The current market for this "fast glass" is largely the portrait / wedding photographer, i.e. people shots. This market still largely produces high quality prints, so I see that this market is going to have to be satisfied before Falk's predictions can be realized.

[Manfred M]

(I think the answer is "no of course it won't", but thought it worth checking).

If you are exclusively showing your images on a computer screen, I would agree with you. If you are doing large, high quality prints, I would be shooting the crop frame for birds in flight. This is where the crop frame D7100 will out performed the cropped 10MP DX version of the image on the D610.

[xpatUSA]

Falk's writeup is good, but is based on the math and physics side of the house. On the flip side, I don't think he has a good grasp of the design, manufacturing, financial, etc. side of things. I think he makes a lot of good points, but also some rather suspect ones.

Where I clearly see a miss is the cost of introducing fast, quality lenses on a crop frame sensor that give the user the equivalent depth of field of a full frame camera (which incidentally was one of the reasons I went full frame). Optically quality on so called "professional" lenses means even more constraints on the lens designer. Most pro zoom lenses have maximum apertures of f/2.8 and generally have zoom factors of less than 3x. Going to an APS-C sized sensor for the same DoF means that we would need f/2 lenses. The current market for this "fast glass" is largely the portrait / wedding photographer, i.e. people shots. This market still largely produces high quality prints, so I see that this market is going to have to be satisfied before Falk's predictions can be realized.

Good point. He does have another paper, specifically about equivalence, where he goes into that side of thing a little more - in particular comparing lens requirements for a given DOF, etc., for example between 135 format and 4/3 format. f/0.95 gets a mention, IIRC.

[billtils]

[QUOTE=the cropped 10MP DX version of the image on the D610.[/QUOTE]

Thanks for replying Manfred. I'm not sure about this part of your answer - Where does the 10MP come from? The 610 has a 24MP sensor, as does the 7100. The lens is a full frame FX series one and would not be cropped in camera. Are you factoring in the fact that the lens would now be functioning as a true 300mm and not a 450?

[Manfred M]

Thanks for replying Manfred. I'm not sure about this part of your answer - Where does the 10MP come from? The 610 has a 24MP sensor, as does the 7100. The lens is a full frame FX series one and would not be cropped in camera. Are you factoring in the fact that the lens would now be functioning as a true 300mm and not a 450?

If comes from an earlier question on this thread that you posted.

2) The D610 has an autocrop mode that will let me use my FX lenses (well, lens singular actually since my prime and longer telephoto zoom are FX ones) but crops to about 10MP; how will that 10MP on the FF sensor compare to the 24 on the FX when it comes to editing the image (including cropping it)?

When you use a FX camera in DX mode, only a part of the sensor is used, with the rest being cropped away. I don't have the D610 manual in front of me, but when I look at my D800 manual I get the following information:

Full frame image is 36MP (7360 x 4912 pixels). If I pop on a DX lens, this drops to 4800 x 3200 piexels (15MP), so the numbers you give for the D610 shooting in crop frame mode are in the right order of magnitude.

A 24MP image that is 23.4mm x 15.6mm in size has a lot higher definition than a 10MP image that is that size. It won't make any real difference on your computer screen, which is likely downsampling the image to somewhere around 2MP (1920 x 1280 display). On the other hand, if you are printing on an inkjet printer with 300 Dots Per Inch (DPI) on Canon or HP or 360 DPI on Epson, both the 24MP and the 10MP images will need considerable upsampling to print at say a 16" x 20" print. You will definitely see the difference in quality if you viewed the two prints made side by side. Do some cropping, and you will see even more of a difference.

[billtils]

Sorry Manfred - my fault, apologies for misleading you. The post you referenced should have said "... autocrop that will let me use my 16-85mm zoom DX lens. The 50mm prime and 70-300mm zoom are full frame FX format". So the question was really comparing what I'd get with the FX zoom on the full frame D610 and the same lens on the DX format D7100. As an aside, I try not to use the lens at focal lengths more than 250mm - the posted image was at 240mm.

[Manfred M]

Sorry Manfred - my fault, apologies for misleading you. The post you referenced should have said "... autocrop that will let me use my 16-85mm zoom DX lens. The 50mm prime and 70-300mm zoom are full frame FX format". So the question was really comparing what I'd get with the FX zoom on the full frame D610 and the same lens on the DX format D7100. As an aside, I try not to use the lens at focal lengths more than 250mm - the posted image was at 240mm.

So what you are really comparing is what an image shot on a 24MP DX (D7100) camera versus a 24MP shot on the FX camera (D610).

The answer I gave is still valid; the smaller sensor D7100 at 300mm would be the equivalent of shooting a 450mm focal length on the D610. If you shot the same lens at 300mm focal length and cropped your image coming out of the D610 so it was the same size as the one out of the D7100, you would be working with around 10MP of data.

So if birding and maximum magnification was your goal, the highest image quality option would continue to be the D7100. A lot of birders, with limited budgets do shoot with APS-C sensors because of this.

Now if I were a birder (and I'm not), with an unlimited budget, and stuck with Nikon I would get a D4s body and have both the 600mm and 800mm lenses. I'd have a 1.4x teleconverter along as well on top of a really heavy duty carbon fibre tripod, likely with a gimbal head.

[billtils]

Yep, I'd get those too, along with a divorce

But thanks for the feedback - it makes sense!